Question:
I've heard about Caucasicum offered through a nutritional MLM. Can you tell me more about it?
Answer:
This information is about the best probiotic and anti-oxidant of which I've learned during my research this year. We were so impressed with its qualities both my husband and I have been using it since January. Its ingredients are far ahead of ordinary yogurt, as made commercially. Because it is in capsule form, it can easily be swallowed by those who don't like yogurt, and want a product which will give them more pro-biotic or friendly bacteria, along with its amazing anti-oxidant properties.
Kefir Caucasicum, is a combination of Kefir grain, which is among the world's first known grains, and a type of yogurt culture derived from Kefir. The end result is a complex, symbiotic mixture of the micro-organisms that indigenous peoples of mid-Eastern countries have been consuming for many centuries. It naturally contains 4 genera and 11 species of probiotic, or friendly, bacteria. It is then freeze-dried at low temperatures, and 2 probiotic growth accelerants are added, recognized as superb. The end result is a complete, alcohol and yeast-free, Kefir complex in every capsule.
The yogurt which most Americans eat is quite basic. The yogurt manufacturers usually add 2 species of friendly bacteria to milk, along with flavorings, sugar, and small amounts of overcooked fruit. It is then bottled in various shapes of containers, and then allowed to ferment in incubators. This is more of a dessert than anything else. Even the plain yogurt, while a good calcium-rich food, is no match for the actual probiotics, or friendly bacteria, contained in the Kefir Caucasicum. However, there is a use in a healthful diet for both the plain, calcium-rich yogurt, and the Kefir Caucasicum.
The other part of Caucasicum Plus is one which helps to give the product its unique properties and astounding healthful benefits. Rhodogen, a Trade- Marked Formula, is an unusual extract from the root of an extremely rare variety of plant named Rhododendron Caucasicum. It is also known as the Snow Rose, and usually grows at altitudes above 7,000 ft. on the Caucacus Mountains in the Republic of Georgia. This was once part of the southern border of the Soviet Union. It is not unusual for people to live beyond 100 years of age in that region. About 40 years ago Soviet scientists launched a full scale research project to discover the reason for this longevity.
It was discovered that the Georgian peoples traditionally brewed the roots of their Snow Rose into what they called Alpine Tea. and added it to their widely used Kefir culture, which proved to be the key to their longevity. The reasons they did so were three-fold. The Alpine Tea or Rhododendron Caucasicum sweetened the Kefir culture, while protecting it from harmful bacteria, or turning rancid before it could be eaten, and they learned over a long period of time that it gave them strength and energy. They also discovered that it protected them from what today we call "free radicals, pathogens, and viruses." But to them it just seemed to ward off many diseases from which their neighbors in surrounding countries were always dying.
The scientists learned that the Rhododendron Caucasicum has many important properties of its own. It improves physical abilities, increases activity of the cardiovascular system, and increases blood supply to muscles and especially to the brain. It also shows tremendous anti- bacterial activity against the harmful bacteria, but allows "friendly" or probiotics, such as are found in Kefir culture, to thrive.
There were many clinical studies and experiments performed over the years in the First Central Moscow Hospital using the Rhododendron Caucasicum alone. These all proved very successful in cases of Heart Disease, Gout, Neuropsychotic (brain) Disease, severe Depression, Capillary fragility, and Detoxicant (increasing discharges of toxins from the body.) The most important discovery, however, was that it was the most tremendously effective ultra-antioxidant or "free radical" scavenger in their experiences.
There are other plant extracts such as pine bark and grape seed, sold under several different product names, that have shown strong anti- oxidant activity. However, they are, by nature, much less effective "free radical" scavengers. Furthermore, the methods of extracting and producing those extracts almost always include the use of organic solvents, which generate highly toxic and powerful "free radicals" them- selves,--the very things the products were meant to destroy. So, much of the scavenging energy of pine bark and grape seed extracts is spent cleaning up the very dangers that they created.
The Rhododendron Caucasicum in CAUCASICUM PLUS is not only a much more effective antioxidant or "free radical" scavenger, but it is also absolutely organic solvent-free, and 100% water soluble.
Also added to the Kefir Caucasicum culture, are concentrated minerals from the waters of the Georgian mountains. Each of these ingredients are incredible by themselves, but when all 3 are combined, the final result is the unique product known as Caucasicum Plus.
Because Caucasicum Plus helps to increase the circulation in the legs, it is a valuable Formula to take on a regular basis. I will Forward a Testimonial to you concerning this.
For further information on Caucasicum Plus, again please look in my Web Site below. Also, if I can help you further in any way, don't hesitate to write me with more questions!
Better Health for YOU, and Everyone!
Carol McKinney
Kefir tanesi
Tuesday, January 30, 2007
Kefir - Milchkefir und Wasserkefir
Wer Kefir trinkt, hat ein längeres Leben wird behauptet. Im Kaukasus, der Heimat der Kefirknolle, die auch Kefirpilz genannt wird, leben viele Menschen bei bester Gesundheit weit über 100 Jahre. Untersuchungen des russischen Nobelpreisträgers Elie Mechnikow belegen eindeutig die gesundheitsförderliche Wirkung von Milchkefir.
Ein anderes schmackhaftes Kefirgetränk ist der Wasserkefir, der mit Kefirkristallen und mit Wasser statt Milch hergestellt wird. Im Alter gesund mit Kefir
Ob man durch den Genuss des Naturprodukts Kefir tatsächlich 100 Jahre wird, sei dahingestellt - auf jeden Fall gehören Milchkefir und Wasserkefir wohl zu den gesündesten Lebensmitteln überhaupt.
Als langjähriger Fan der Kefirknolle und der Wasserkefirkristalle möchte ich auf dieser Seite den Milchkefir seinen Verwandten, den Wasserkefir, vorstellen. Da sich der Kefirpilz und auch die Kefirkristalle vermehren, gebe ich auch gern etwas an Leute ab, die neugierig geworden sind und etwas für ihre Gesundheit tun möchten.
Ein anderes schmackhaftes Kefirgetränk ist der Wasserkefir, der mit Kefirkristallen und mit Wasser statt Milch hergestellt wird. Im Alter gesund mit Kefir
Ob man durch den Genuss des Naturprodukts Kefir tatsächlich 100 Jahre wird, sei dahingestellt - auf jeden Fall gehören Milchkefir und Wasserkefir wohl zu den gesündesten Lebensmitteln überhaupt.
Als langjähriger Fan der Kefirknolle und der Wasserkefirkristalle möchte ich auf dieser Seite den Milchkefir seinen Verwandten, den Wasserkefir, vorstellen. Da sich der Kefirpilz und auch die Kefirkristalle vermehren, gebe ich auch gern etwas an Leute ab, die neugierig geworden sind und etwas für ihre Gesundheit tun möchten.
Faruk BEŞER fbeser@stargazete.com Kefir içen káfir mi olur?
Başlığa takılmayın, onu sırf cinas olsun diye söyledim. Yoksa şarap içen dahi sadece içmekle káfir olmaz.
Kefir denen içeceğin helal olup olmadığı konusunda çok soru almış, ama bir türlü cevaplama imkánı bulamamıştım. Şimdi hepsine birden cevap vermiş olayım.
Kefir, özel bir maya mantarıyla, keçi veya inek sütünün mayalanmasıyla hazırlanan ayrana benzer ekşi bir içecektir.
Çok eski yıllardan beri özellikle Kafkasya bölgesinde bilinmekte, bugün ise dünyanın her tarafında tanınmaktadır. Bileşiminde yüzde 0.6-1.1 oranında etil alkol oluşur. Çok faydalı olduğu söylenen bir içecektir.
Bilindiği gibi İslam’da sarhoş edici içecekler haramdır. Çünkü alkol beyin hücrelerini tahrip edip insanın aklına zarar verir. Akıl ise İslam’ın öncelikle korumayı hedeflediği beş temel değerden biridir. İçki yasağını konu edinen ayeti kerime Allah ‘çünkü onun zararı faydasından çok daha büyüktür’ der. Demek ki faydası zararından fazla olsaydı muhtemelen yasaklanmayacaktı. Çünkü İslam, insan için zararlı olanları defetmek, faydalı olanları celbetmek için vardır. Ve zararın giderilmesi daha önceliklidir.
Buradan İslam fıkıhçıları bir kural geliştirmişlerdir: ‘Hükmü kıyasla da olsa Kur’an’da ve Sünnet’te zikredilmeyen, sonradan ortaya çıkan yiyecek ve içeceklerdeki meşruiyet ölçüsü, zararlı olup olmamasıdır. Zararlı ise haramdır, değilse helaldir.’
Bir başka kural şudur: İslam, alkolü değil, sarhoş edicileri yasaklamıştır. Oysa alkolün şöyle ya da böyle bulunmadığı hemen hiçbir gıda yoktur. Meyvelerde bile bulunur. Ölçü şudur: ‘Bir içkinin çoğu sarhoş ediyorsa azı da haramdır.’
Buradan biz İslam’ın bir laboratuar dini, bir elit dini olmadığını da anlıyoruz. Onun ölçülerini en sade insan dahi anlamalıdır. Çoban dahi içildiğinde sarhoş eden içecekleri tecrübe ile bilir ve inanıyorsa kaçınır.
Eğer kefir laboratuar tahlillerinin olmadığı zamanlarda ortaya çıkmış olsaydı o zamanın fakihleri onun hükmünü ancak bu ölçü ile vereceklerdi.
Kurá’n-ı Kerim’in sarhoş edicileri şeytan işi bir pislik ilan ettiği doğrudur. Ancak bu pisliğin maddi bir pislik mi yoksa ahlaki ve manevi bir pislik mi olduğu çok açık değildir. Fıkıhçıların çoğunluğu, ihtiyatlı davranıp sarhoş edicileri aynı zamanda maddi bir pislik sayarlar ve insanın üzerine bulaşması durumunda onunla namaz kılınamayacağını, yiyeceklere düşmesi halinde onu pisleteceğini ve yenmez kılacağını söylerler. Buna itiraz edecek değiliz. Ancak içine sarhoş edici içki katılan gıda ile, içinde kendiliğinden bir miktar alkol oluşan gıda aynı değildir.
Kefire alkol katılmamaktadır, içinde çok az bir miktar alkol oluşmaktadır ve bu miktar da onu sarhoş edici bir içki kılmamaktadır. Boza da böyledir. Ama biranın çoğu sarhoş eder, o halde azı da haramdır.
Diğer yönden kefirin faydaları zararlarıyla kıyaslanmayacak kadar çoktur.
Gıdalar konusunda bilmemiz gereken önemli bir kural da şudur: İkisi de hata olmakla beraber; helal daireyi daraltıp bazı helallere haram demek, haramları daraltıp bazı haramlara helal demekten çok daha büyük bir hatadır. Çünkü bu tavır, hayatı yaşanmaz kılar ve insanlarda harama karşı duyarlığı zayıflatır.
O halde kefir İslam’ın yasakladığı sarhoş edicilerden değildir.
Afiyet olsun
Kefir denen içeceğin helal olup olmadığı konusunda çok soru almış, ama bir türlü cevaplama imkánı bulamamıştım. Şimdi hepsine birden cevap vermiş olayım.
Kefir, özel bir maya mantarıyla, keçi veya inek sütünün mayalanmasıyla hazırlanan ayrana benzer ekşi bir içecektir.
Çok eski yıllardan beri özellikle Kafkasya bölgesinde bilinmekte, bugün ise dünyanın her tarafında tanınmaktadır. Bileşiminde yüzde 0.6-1.1 oranında etil alkol oluşur. Çok faydalı olduğu söylenen bir içecektir.
Bilindiği gibi İslam’da sarhoş edici içecekler haramdır. Çünkü alkol beyin hücrelerini tahrip edip insanın aklına zarar verir. Akıl ise İslam’ın öncelikle korumayı hedeflediği beş temel değerden biridir. İçki yasağını konu edinen ayeti kerime Allah ‘çünkü onun zararı faydasından çok daha büyüktür’ der. Demek ki faydası zararından fazla olsaydı muhtemelen yasaklanmayacaktı. Çünkü İslam, insan için zararlı olanları defetmek, faydalı olanları celbetmek için vardır. Ve zararın giderilmesi daha önceliklidir.
Buradan İslam fıkıhçıları bir kural geliştirmişlerdir: ‘Hükmü kıyasla da olsa Kur’an’da ve Sünnet’te zikredilmeyen, sonradan ortaya çıkan yiyecek ve içeceklerdeki meşruiyet ölçüsü, zararlı olup olmamasıdır. Zararlı ise haramdır, değilse helaldir.’
Bir başka kural şudur: İslam, alkolü değil, sarhoş edicileri yasaklamıştır. Oysa alkolün şöyle ya da böyle bulunmadığı hemen hiçbir gıda yoktur. Meyvelerde bile bulunur. Ölçü şudur: ‘Bir içkinin çoğu sarhoş ediyorsa azı da haramdır.’
Buradan biz İslam’ın bir laboratuar dini, bir elit dini olmadığını da anlıyoruz. Onun ölçülerini en sade insan dahi anlamalıdır. Çoban dahi içildiğinde sarhoş eden içecekleri tecrübe ile bilir ve inanıyorsa kaçınır.
Eğer kefir laboratuar tahlillerinin olmadığı zamanlarda ortaya çıkmış olsaydı o zamanın fakihleri onun hükmünü ancak bu ölçü ile vereceklerdi.
Kurá’n-ı Kerim’in sarhoş edicileri şeytan işi bir pislik ilan ettiği doğrudur. Ancak bu pisliğin maddi bir pislik mi yoksa ahlaki ve manevi bir pislik mi olduğu çok açık değildir. Fıkıhçıların çoğunluğu, ihtiyatlı davranıp sarhoş edicileri aynı zamanda maddi bir pislik sayarlar ve insanın üzerine bulaşması durumunda onunla namaz kılınamayacağını, yiyeceklere düşmesi halinde onu pisleteceğini ve yenmez kılacağını söylerler. Buna itiraz edecek değiliz. Ancak içine sarhoş edici içki katılan gıda ile, içinde kendiliğinden bir miktar alkol oluşan gıda aynı değildir.
Kefire alkol katılmamaktadır, içinde çok az bir miktar alkol oluşmaktadır ve bu miktar da onu sarhoş edici bir içki kılmamaktadır. Boza da böyledir. Ama biranın çoğu sarhoş eder, o halde azı da haramdır.
Diğer yönden kefirin faydaları zararlarıyla kıyaslanmayacak kadar çoktur.
Gıdalar konusunda bilmemiz gereken önemli bir kural da şudur: İkisi de hata olmakla beraber; helal daireyi daraltıp bazı helallere haram demek, haramları daraltıp bazı haramlara helal demekten çok daha büyük bir hatadır. Çünkü bu tavır, hayatı yaşanmaz kılar ve insanlarda harama karşı duyarlığı zayıflatır.
O halde kefir İslam’ın yasakladığı sarhoş edicilerden değildir.
Afiyet olsun
Kefir neye iyi gelir
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Bağırsaklardaki maddelerin küreselleşmesini önler
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Beyine enerji verir ve zihinsel gelişimi sağlar
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Kansere karşı koruyucu ve kanseri geciktirici etkisi vardır
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Yüksek tansiyonu giderir
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Kolesterolü düşürür
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Damar sertliğini giderir
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Kemik erimesini önler
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Bronşit ve astım nöbetlerini azaltır
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Kansızlığı ve kan bozukluğunu giderir
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Mikrobik enfeksiyonlara karşı direnci arttırır
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Egzama ve alerjilerde faydalıdır
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İdrar yolu iltihaplarını tedavi eder
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İdrarı sulandırır
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Karaciğer bozukluğunu tedavi eder
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Mide ve bağırsak salgılarını arttırıp hazmı kolaylaştırır
Bağırsak hareketlerini hızlandırır
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Mide ve bağırsak rahatsızlıklarına iyi gelir
Bağırsaklardaki maddelerin küreselleşmesini önler
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Beyine enerji verir ve zihinsel gelişimi sağlar
#
Kansere karşı koruyucu ve kanseri geciktirici etkisi vardır
#
Yüksek tansiyonu giderir
#
Kolesterolü düşürür
#
Damar sertliğini giderir
#
Kemik erimesini önler
#
Bronşit ve astım nöbetlerini azaltır
#
Kansızlığı ve kan bozukluğunu giderir
#
Mikrobik enfeksiyonlara karşı direnci arttırır
#
Egzama ve alerjilerde faydalıdır
#
İdrar yolu iltihaplarını tedavi eder
#
İdrarı sulandırır
#
Karaciğer bozukluğunu tedavi eder
#
Mide ve bağırsak salgılarını arttırıp hazmı kolaylaştırır
Bağırsak hareketlerini hızlandırır
#
Mide ve bağırsak rahatsızlıklarına iyi gelir
Kefir Nedir?
İnsanlar kendi hücrelerinin 10 katı sayıdaki (100 trilyon) faydalı bağırsak mikrobu ile ortak bir yaşam sürdürmektedir. Faydalı bağırsak mikropları (probiyotikler) çeşitli yararlarının yanında dış ortamdan gelen zehirli maddelerin kana geçmesini engelleyen koruyucu bir bağırsak tabakası oluştururlar. Bağırsaktaki sağlıklı mikrop dengesinin, zararlı mikroplar lehine değişmesi, yani bağırsaktaki mükemmel dengenin bozulması çok sayıda ivegen ve müzmin hastalığa yol açar.
Son yıllarda rafine gıdaların tüketimindeki artışa paralel olarak, turşu, kefir, boza, çeşitli salamuralar gibi geleneksel fermantasyon gıdalarının az tüketilmesi, süt ve yoğurt gibi fazla tüketilenlerin ise ekşimesin ya da kesmesin diye pastörize edilmesi ya da antibiyotik katılması vücudumuzun mükemmel probiyotik dengesini alt üst etmiştir.
Probiyotik - Prebiyotik
Yeterli miktarda yenildiğinde insan ya da hayvan sağlığını olumlu yönde etkileyen mikroorganizmalara probiyotik denir.
Bağırsaktaki bazı mikroorganizmaların çoğalmasını artıran ve/veya aktivitesini uyaran ve insan ya da hayvan sağlığını olumlu yönde etkileyen maddelere (besinsel lifler gibi) prebiyotik denir
Probiyotikler = yararlı bağırsak mikropları (bakteriler ve mantarlar)
Erişkin bir insan bağırsağında 100 trilyon (1,5 kg) faydalı bakteri ve mantar bulunur. Bu rakam insan hücre sayısının 10 katı kadardır.
Sayıları 400’ün üzerinde olan bu bakteriler ve mantarlar normal bağırsak florasını oluştururlar.
Bu bakteriler ve mantarlar 300 m2 büyüklüğünde bir yüzey oluşturan bağırsak sümüksü zarını koruyucu bir tabaka şeklinde döşer.
Probiyotiklerin görevleri
- Bağışıklık sistemini güçlendirmek.
- Yiyeceklerin hazmını kalaylaştırmak.
- Vitaminlerin (K vit, biyotin, B12, niasin vb) sentezini yapmak.
- Bağırsak duvarını zararlı maddelerden korumak ve bağırsak geçirgenliğini azaltmak.
- Zararlı maddelerin (toksinler) kan dolaşımına geçmesini engellemek.
- Besin allerjilerini ve ekzemayı önlemek.
- Kronik enflamatuvar (iltihabi) hastalıkların oluşumunu engellemek.
- Kanseri önlemek.
- Yaşlanmayı yavaşlatmak.
- Depresyonu hafifletmek.
- Otizm bulgularını hafifletmek.
- İshali önlemek ve tedavi etmek.
- İdrar yolu iltihaplarını önlemek.
- Kabızlığı tedavi etmek.
- Böbrek taşlarının (okzalat) oluşumunu azaltmak.
Kefir nasıl yapılır?
Kefir yapılışında kullanılan süt kaynatılır ve metal olmayan (tercihan cam) bir kap içinde ılıtılır (süt temiz ise kaynatılmayabilir).
Üzerindeki kaymak tabakası alınır ve 1 çorba kaşığı kadar kefir mayası atılır ve süt iyice karıştırılır.
Kabın kapağı kapatılır ve süt 20-25 C 'de kalacak şekilde kap bir yere bırakılır. Mayalanacak kab soba ya da kalorifer yakınına getirilir. Çevre ısısı düşük ise kabın etrafı bezle sarılır. Kabın 20-30°C' lerde olması sağlanır. Kap içindeki süt normal olarak 18-24 saat sonra pıhtılaşır. Maya miktarı düşük ve ortam soğuk ise pıhtılaşma gecikir. Mayalanmış süt madeni olmayan bir tel süzgeçten ya da tülbentten süzülür. Süzgeç üzerinde kalan daneler tekrar maya olarak kullanılır. Kefir mayası (taneleri) hemen kullanılmayacaksa ağzı kapalı bir cam kavanoz içinde buzdolabında saklanır. Bazıları kefir tanelerini saklamadan önce yıkarlar. Eğer yıkama yapacaksanız kefir tanelerinin zarar görmemesi için klorsuz su kullanın. Saklanmak istendiği zaman daneleri örtecek kadar bardağa su koymak gerekir.
Kefir neye benzer?
Kefir yoğurda ya da ayrana benzer. Zaten benzer şekilde mayalanır. Bekletildikçe tadı ekşir ve çok az olan alkol oranı artar.
Kefirin zararı var mı?
Kefirin bilinen bir zararı yoktur. Çok nadir olarak bazı kişiler yeni başladıklarında fazla kefir içmeye tahammül edemezler. Bu kişiler kefir miktarını yavaş yavaş artırmalıdır. Bazı kişiler toksinlerden temizlenirken toksinlerin geçtiği dokularda bir takım rahatsızlıklar oluşabilir. Kısa bir süre sonra, toksinler vücut dışına çıkacak ve kişi kendini çok iyi hissedecektir (iyileşme krizi).
Kefir tanelerini nereden temin edebilirim?
Kefir tanelerini, Ege Ziraat fakültesi gibi bazı fakültelerden, aktarlardan ya da tanıdıklarınızdan temin edebilirsiniz.
Bazı firmalar hazır kefir de satmaya başlamıştır.
Kefirinizin ucuz ve istediğiniz kıvamda olması için mümkünse kendiniz yapın.
Kefir taneleri neye benzer?
Kefir taneleri karnabahar görünümünde fakat lastik kıvamındadır. Kefir tanelerinin dışında kefiran denilen bir yapışkan bir zar(f) vardır. Yararlı bakteriler ve mantarlar kendi yaptıkları bu zarın içinde yaşarlar
Kefir taneleri çok büyümüşse kesilmeli mi?
Kefir taneleriniz büyük ise bunu kesmeyin, aksi halde kefiran metalden zarar görebilir. En iyisi hafifçe elinizle sıkmadan ayırmaktır.
Kefir taneleri sonsuza kadar yaşayabilir mi?
Kuru kefir taneleri birkaç mayalamadan sonra yok olabilir. Ama ıslak maya eğer iyi bakılırsa sonsuza kadar sağlıklı kalır (şimdiye kadar nasıl geldi!) Kefir tanelerini sıkmayın, metal değdirmeyin, temiz tutun. Uzun süre kullanmayacaksanız soğuk bir yerde (tercihan buzdolabında) tutun. Daha uzun süre saklamak istiyenler derin dondurucuya koyabilirler.
Kefir tanelerini daha çabuk nasıl büyütebilirim?
Mayanın miktarı ne kadar fazla ve mayalama süresi ne kadar uzunsa kefir taneleri de o kadar büyük olur. Fakat belli bir noktadan sonra üreme yavaşlar. Tane ve su ayrılırsa tekrar ekilirse taneler daha çabuk büyür.
Kefirin tam olarak mayalandığını nasıl anlarım?
Bu genellikle oda sıcaklığında 24 saat içinde gerçekleşir. Kefir tanelerine kürdan sokun. Ayakta duruyorsa kefir mayalanmıştır. Mayaladığınız kefirde taneler (yukarıda) ile peyniraltı suyu (whey) (aşağıda) arasındaki sınır keskinleşmişse kefir olmuştur.
Kefirin tadını ve kıvamını ayarlamak için ne yapayım?
Kefiriniz tatlı ise ve ekşi seviyorsanız mayalanma süresini 48 saate kadar uzatın. Kefir ekşidikçe faydası artar. Ayrıca alkol miktarı da artar. Tatlı kefir istiyorsanız mayalanma süresin 24 saatten fazla uzatmayın ve kefiri buzdolabında saklayın. Kefirinizin daha katı olmasın istiyorsanız ayırdığınız kefir ayranını birkaç saat buzdolabında tutun.
Kefir yapmayı bir süre ertelemek istiyorsam ne yapayım?
Eğer bir süre kefir yapmayacaksanız, mayayı buzdolabının rafına koyun. Böylece kefirin üremesi yavaşlayacaktır. Birkaç gün bu şekilde fazla değişmeden durabilir. Eğer daha uzun süre tutmak istiyorsanız, kefir tanelerini örtecek kadar kaba süt koyun ve kabı dondurucuya koyun. Böylelikle birkaç hafta süre ile kefir aşırı bir üreme göstermez.
Kefir için hangi sütü kullanayım?
En tercih edileni Eski ve Orta Asya Türklerinin yaptığı gibi çiğ keçi sütüdür. Diğer hayvanların sütü de olabilir. Yemlenen değil otlayan hayvanların sütünü tercih edin. Market sütleri iyi bir tercih değildir. Bunlar içinden günlük şişe sütlerini tercih edin. Kutu sütlerini tercih etmeyin (zaten bazıları da mayalanmıyor).
Ne kadar kefir tüketmeliyim?
Ne kadar yoğurt yiyorsanız o kadar. Önce bir çay bardağı için sonra miktar gittikçe arttırın. Genellikle 250-1000 mL kadar tüketilmektedir. Müzmin hastalığı olan kişilerin en az bir litre kadar kullanması tavsiye edilmektedir.
Sıcak yemeklere kefir konulur mu?
Kefir sıcak yemeklerin üzerine eklenebilir ve hatta pişirilebilir de. Kefirden maksimal etkiyi sağlayabilmek istiyorsanız ısıya maruz bırakmayın. Çünkü bu içindeki faydalı mikropları öldürecektir.
Süt dışı maddelerle de kefir yapılabilir mi?
Evet yapılabilir. Fakat verilen sıvının içinde kefir mikroplarının hayatiyetini sürdürebileceği herhangi bir şeker bulunmalıdır. Meyve suyu ya da şekerli su ile yapılan kefire su kefiri denmektedir. Bu kefirlerin mayalanması genellikle daha uzun sürmektedir.
Kefir ile yoğurdun farkları nelerdir?
Her ikisi de sütün fermantasyonu sonucu elde edilir. Görünüş olarak birbirlerine çok benzerler Yoğurt prebiyotiktir yani probiyotiklerin üremesini artarır. Kefir probiyotiktir. Yani kendisi yararlı mikroorganizmadır.
Yoğurtta mikroorganizma olarak sadece bifidobakterler ve laktobasiller bulunur (market yoğurdu ise onlar da yok !!). Kefirde ise bunlara ilaveten Lactobacillus Caucasus, Leuconostoc, asetobacter ve streptokok gibi bakteriler ile Saccharomyces kefir and Torula kefir gibi mantarlar bulunur. Sonuç olarak evde yapılan yoğurt sağlığınız için çok iyidir kefir ise ondan da iyidir.
Kefir ve kanser
Kefir tümör oluşumunu engellemekte ya da var olanın ilerlemesini azaltmaktadır.
Kefir ve vitaminler
Kefir içindeki mikroorganizmalar bol miktarda vitamin (K vit, B1 vitamini, pan-totenik asit, niasin, folik asit B12, ve biyotin) sentezi yapar-lar. Kefir mikroorganizmalarının ürettiği biyotin diğer B kompleks vitaminlerinin emilimini de artırır.
Prof.Dr. Ahmet AYDIN
Son yıllarda rafine gıdaların tüketimindeki artışa paralel olarak, turşu, kefir, boza, çeşitli salamuralar gibi geleneksel fermantasyon gıdalarının az tüketilmesi, süt ve yoğurt gibi fazla tüketilenlerin ise ekşimesin ya da kesmesin diye pastörize edilmesi ya da antibiyotik katılması vücudumuzun mükemmel probiyotik dengesini alt üst etmiştir.
Probiyotik - Prebiyotik
Yeterli miktarda yenildiğinde insan ya da hayvan sağlığını olumlu yönde etkileyen mikroorganizmalara probiyotik denir.
Bağırsaktaki bazı mikroorganizmaların çoğalmasını artıran ve/veya aktivitesini uyaran ve insan ya da hayvan sağlığını olumlu yönde etkileyen maddelere (besinsel lifler gibi) prebiyotik denir
Probiyotikler = yararlı bağırsak mikropları (bakteriler ve mantarlar)
Erişkin bir insan bağırsağında 100 trilyon (1,5 kg) faydalı bakteri ve mantar bulunur. Bu rakam insan hücre sayısının 10 katı kadardır.
Sayıları 400’ün üzerinde olan bu bakteriler ve mantarlar normal bağırsak florasını oluştururlar.
Bu bakteriler ve mantarlar 300 m2 büyüklüğünde bir yüzey oluşturan bağırsak sümüksü zarını koruyucu bir tabaka şeklinde döşer.
Probiyotiklerin görevleri
- Bağışıklık sistemini güçlendirmek.
- Yiyeceklerin hazmını kalaylaştırmak.
- Vitaminlerin (K vit, biyotin, B12, niasin vb) sentezini yapmak.
- Bağırsak duvarını zararlı maddelerden korumak ve bağırsak geçirgenliğini azaltmak.
- Zararlı maddelerin (toksinler) kan dolaşımına geçmesini engellemek.
- Besin allerjilerini ve ekzemayı önlemek.
- Kronik enflamatuvar (iltihabi) hastalıkların oluşumunu engellemek.
- Kanseri önlemek.
- Yaşlanmayı yavaşlatmak.
- Depresyonu hafifletmek.
- Otizm bulgularını hafifletmek.
- İshali önlemek ve tedavi etmek.
- İdrar yolu iltihaplarını önlemek.
- Kabızlığı tedavi etmek.
- Böbrek taşlarının (okzalat) oluşumunu azaltmak.
Kefir nasıl yapılır?
Kefir yapılışında kullanılan süt kaynatılır ve metal olmayan (tercihan cam) bir kap içinde ılıtılır (süt temiz ise kaynatılmayabilir).
Üzerindeki kaymak tabakası alınır ve 1 çorba kaşığı kadar kefir mayası atılır ve süt iyice karıştırılır.
Kabın kapağı kapatılır ve süt 20-25 C 'de kalacak şekilde kap bir yere bırakılır. Mayalanacak kab soba ya da kalorifer yakınına getirilir. Çevre ısısı düşük ise kabın etrafı bezle sarılır. Kabın 20-30°C' lerde olması sağlanır. Kap içindeki süt normal olarak 18-24 saat sonra pıhtılaşır. Maya miktarı düşük ve ortam soğuk ise pıhtılaşma gecikir. Mayalanmış süt madeni olmayan bir tel süzgeçten ya da tülbentten süzülür. Süzgeç üzerinde kalan daneler tekrar maya olarak kullanılır. Kefir mayası (taneleri) hemen kullanılmayacaksa ağzı kapalı bir cam kavanoz içinde buzdolabında saklanır. Bazıları kefir tanelerini saklamadan önce yıkarlar. Eğer yıkama yapacaksanız kefir tanelerinin zarar görmemesi için klorsuz su kullanın. Saklanmak istendiği zaman daneleri örtecek kadar bardağa su koymak gerekir.
Kefir neye benzer?
Kefir yoğurda ya da ayrana benzer. Zaten benzer şekilde mayalanır. Bekletildikçe tadı ekşir ve çok az olan alkol oranı artar.
Kefirin zararı var mı?
Kefirin bilinen bir zararı yoktur. Çok nadir olarak bazı kişiler yeni başladıklarında fazla kefir içmeye tahammül edemezler. Bu kişiler kefir miktarını yavaş yavaş artırmalıdır. Bazı kişiler toksinlerden temizlenirken toksinlerin geçtiği dokularda bir takım rahatsızlıklar oluşabilir. Kısa bir süre sonra, toksinler vücut dışına çıkacak ve kişi kendini çok iyi hissedecektir (iyileşme krizi).
Kefir tanelerini nereden temin edebilirim?
Kefir tanelerini, Ege Ziraat fakültesi gibi bazı fakültelerden, aktarlardan ya da tanıdıklarınızdan temin edebilirsiniz.
Bazı firmalar hazır kefir de satmaya başlamıştır.
Kefirinizin ucuz ve istediğiniz kıvamda olması için mümkünse kendiniz yapın.
Kefir taneleri neye benzer?
Kefir taneleri karnabahar görünümünde fakat lastik kıvamındadır. Kefir tanelerinin dışında kefiran denilen bir yapışkan bir zar(f) vardır. Yararlı bakteriler ve mantarlar kendi yaptıkları bu zarın içinde yaşarlar
Kefir taneleri çok büyümüşse kesilmeli mi?
Kefir taneleriniz büyük ise bunu kesmeyin, aksi halde kefiran metalden zarar görebilir. En iyisi hafifçe elinizle sıkmadan ayırmaktır.
Kefir taneleri sonsuza kadar yaşayabilir mi?
Kuru kefir taneleri birkaç mayalamadan sonra yok olabilir. Ama ıslak maya eğer iyi bakılırsa sonsuza kadar sağlıklı kalır (şimdiye kadar nasıl geldi!) Kefir tanelerini sıkmayın, metal değdirmeyin, temiz tutun. Uzun süre kullanmayacaksanız soğuk bir yerde (tercihan buzdolabında) tutun. Daha uzun süre saklamak istiyenler derin dondurucuya koyabilirler.
Kefir tanelerini daha çabuk nasıl büyütebilirim?
Mayanın miktarı ne kadar fazla ve mayalama süresi ne kadar uzunsa kefir taneleri de o kadar büyük olur. Fakat belli bir noktadan sonra üreme yavaşlar. Tane ve su ayrılırsa tekrar ekilirse taneler daha çabuk büyür.
Kefirin tam olarak mayalandığını nasıl anlarım?
Bu genellikle oda sıcaklığında 24 saat içinde gerçekleşir. Kefir tanelerine kürdan sokun. Ayakta duruyorsa kefir mayalanmıştır. Mayaladığınız kefirde taneler (yukarıda) ile peyniraltı suyu (whey) (aşağıda) arasındaki sınır keskinleşmişse kefir olmuştur.
Kefirin tadını ve kıvamını ayarlamak için ne yapayım?
Kefiriniz tatlı ise ve ekşi seviyorsanız mayalanma süresini 48 saate kadar uzatın. Kefir ekşidikçe faydası artar. Ayrıca alkol miktarı da artar. Tatlı kefir istiyorsanız mayalanma süresin 24 saatten fazla uzatmayın ve kefiri buzdolabında saklayın. Kefirinizin daha katı olmasın istiyorsanız ayırdığınız kefir ayranını birkaç saat buzdolabında tutun.
Kefir yapmayı bir süre ertelemek istiyorsam ne yapayım?
Eğer bir süre kefir yapmayacaksanız, mayayı buzdolabının rafına koyun. Böylece kefirin üremesi yavaşlayacaktır. Birkaç gün bu şekilde fazla değişmeden durabilir. Eğer daha uzun süre tutmak istiyorsanız, kefir tanelerini örtecek kadar kaba süt koyun ve kabı dondurucuya koyun. Böylelikle birkaç hafta süre ile kefir aşırı bir üreme göstermez.
Kefir için hangi sütü kullanayım?
En tercih edileni Eski ve Orta Asya Türklerinin yaptığı gibi çiğ keçi sütüdür. Diğer hayvanların sütü de olabilir. Yemlenen değil otlayan hayvanların sütünü tercih edin. Market sütleri iyi bir tercih değildir. Bunlar içinden günlük şişe sütlerini tercih edin. Kutu sütlerini tercih etmeyin (zaten bazıları da mayalanmıyor).
Ne kadar kefir tüketmeliyim?
Ne kadar yoğurt yiyorsanız o kadar. Önce bir çay bardağı için sonra miktar gittikçe arttırın. Genellikle 250-1000 mL kadar tüketilmektedir. Müzmin hastalığı olan kişilerin en az bir litre kadar kullanması tavsiye edilmektedir.
Sıcak yemeklere kefir konulur mu?
Kefir sıcak yemeklerin üzerine eklenebilir ve hatta pişirilebilir de. Kefirden maksimal etkiyi sağlayabilmek istiyorsanız ısıya maruz bırakmayın. Çünkü bu içindeki faydalı mikropları öldürecektir.
Süt dışı maddelerle de kefir yapılabilir mi?
Evet yapılabilir. Fakat verilen sıvının içinde kefir mikroplarının hayatiyetini sürdürebileceği herhangi bir şeker bulunmalıdır. Meyve suyu ya da şekerli su ile yapılan kefire su kefiri denmektedir. Bu kefirlerin mayalanması genellikle daha uzun sürmektedir.
Kefir ile yoğurdun farkları nelerdir?
Her ikisi de sütün fermantasyonu sonucu elde edilir. Görünüş olarak birbirlerine çok benzerler Yoğurt prebiyotiktir yani probiyotiklerin üremesini artarır. Kefir probiyotiktir. Yani kendisi yararlı mikroorganizmadır.
Yoğurtta mikroorganizma olarak sadece bifidobakterler ve laktobasiller bulunur (market yoğurdu ise onlar da yok !!). Kefirde ise bunlara ilaveten Lactobacillus Caucasus, Leuconostoc, asetobacter ve streptokok gibi bakteriler ile Saccharomyces kefir and Torula kefir gibi mantarlar bulunur. Sonuç olarak evde yapılan yoğurt sağlığınız için çok iyidir kefir ise ondan da iyidir.
Kefir ve kanser
Kefir tümör oluşumunu engellemekte ya da var olanın ilerlemesini azaltmaktadır.
Kefir ve vitaminler
Kefir içindeki mikroorganizmalar bol miktarda vitamin (K vit, B1 vitamini, pan-totenik asit, niasin, folik asit B12, ve biyotin) sentezi yapar-lar. Kefir mikroorganizmalarının ürettiği biyotin diğer B kompleks vitaminlerinin emilimini de artırır.
Prof.Dr. Ahmet AYDIN
METHODS FOR SHIPPING KEFIR GRAINS for SHARING PURPOSES for both milk-based, and water-based kefir grains
Below are details explaining methods for shipping [by post] both milk-based or water-based kefir grains by postal or courier services.
Part 1 Describes three preferred systems used by the sender to prepare kefir grains ready for postage. The first system includes directions for shipping translucent water kefir grains.
Part 2 Explains the process and methods for reactivating kefir grains by the recipient at the receiving end.
PREPARING KEFIR-GRAINS TO POST IN FRESH FORM
For preparing milk-based or water-based kefir grains
Shipping kefir grains, which may take between 1 - 3 days to reach their destination [by post e.g.], may be sent fresh, by placing the grains in either a solution of sweet whey or with fresh milk [for milk-based grains only]. Water kefir grains may be shipped in a 3% sugar-water solution. The container of choice is a 100 - 200 ml [1/3- 3/4 cup] food-grade plastic bottle [obtainable from pharmacies]. Alternatively an empty plastic cola drink or mineral water bottle may be used.
Preparing traditional milk-based kefir grains:
Fill the bottle approx. 3/4 with a solution prepared with pre-boiled cooled water, mixed with 1-2 tsp of whey powder. Or fill the bottle 3/4 full with fresh milk. Add 1 - 2 tbs of kefir grains. Make sure not to fill the bottle more than approx. 90% with kefir grains + solution. Squeeze the bottle with one hand until the liquid reaches the rim. While holding the bottle with one hand [while still squeezing], place and secure the lid tightly with the other hand. The bottle should be left with little to no air gap. This procedure leaves the plastic bottle slightly distorted due to a partial vacuum. This is performed so as any CO2 gas is produced during transit, the pressure expands the bottle, forcing it back to its uniform state, and not cause the bottle to bulge out due to excessive pressure. This simple procedure reduces the potential risk of excessive pressure buildup during transit.
Preparing translucent water-kefir-grains [traditional Sugary Kefir Grains]:
The method explained above may be implemented for shipping fresh translucent water kefir grains [WKG], only if shipping time does not exceed 7-10 days. When shipping WKG, the preferred medium for shipping is prepared with a solution of water and sugar [not whey or dairy milk]. Approx. 2 tsp of sugar [sucrose] to 250 ml [1 cup] of water, plus 3 tbs of translucent WKG has worked well. An alternative medium may be prepared with 1 - 2 tsp of molasses with 250 ml of water. The latter solution produces less CO2 gas, which is favourable by reducing pressure buildup during transit.
NOTES: WKG should remain viable when shipped fresh, as explained above, for up to 10 days at ambient temperature.
SHIPPING PARTIALLY DEHYDRATED KEFIR GRAINS [please see footnotes]
For milk-based kefir grains only
Milk-Kefir grains may be shipped in a partially dehydrated state. This is useful when shipping time may exceed 5 days.
To partially dehydrate [PD] kefir grains, place the grains in a strainer and rinse with Chlorine-free clean COLD water to remove protein deposits from the surface of the grains. Alternatively, the grains may be placed in a bowl filled with fresh cold water and the grains are gently stirred to remove protein deposits from the surface of each grain. Pour the contents into a strainer to drain away the water and recover the washed grains. Gently pat-dry the grains by placing between a sheet of paper or cotton toweling. Finally, place the grains between two sheets of thin cloth or paper toweling. Keep in a warm spot with good ventilation and let dry at room temperature for 24 hours. Mix 2 parts by volume of *dry milk powder [DMP] with 1 part PD kefir grains. The PD kefir grains + DMP mixture is placed in a ziplock plastic bag and shipped in this state. Kefir grains shipped in this state will remain viable for approx. 2 months, depending on the extent of dehydration [the drier the grains, the longer they will store].
I use an electric-driven heat controllable food dehydrator to partially dehydrate kefir grains. Dehydrating at 25° C [77° F] for approx. 2 hours [until the outer-surface of the grains dehydrate]. This is performed so that the DMP does not adhere to the surface of the grains and to reduce water content.
Any form of dry milk powder may be used i.e. full cream or non fat, cow or goat's milk etc.
NOTES:This shipping method was investigated by a Professor of Microbiology, Professor J. M. Schneedorf, whom at the time was researching kefir at the University of Alfenas, Brazil. The parcel took approx. 2 weeks to reach the Professor by post. The grains were healthy and grew well in his laboratory. He also found that there was no evidence of any microbes, yeasts or molds cultivable from the actual DMP removed from the grains, after 4 days culturing under laboratory conditions.
This was likely due to initially sterilizing the DMP, before mixed with PD kefir grains. Sterilization was performed by toasting the DMP in a hot iron skillet for approx. 3 minutes [while continuously stirring the DMP]. Rapid cooling the sterile DMP to ambient temperature and then mixing the DMP with the PD kefir grains. The mixture was placed in a ziplock plastic bag before posting by regular airmail.
SHIPPING FULLY DEHYDRATED KEFIR GRAINS
Instructions for dehydrating Milk Kefir Grains
To fully dehydrate kefir grains, place the grains in a strainer and wash with Chlorine-free clean COLD water, to remove protein deposits from the surface of the grains. Alternatively, the grains may be placed in a bowl filled with fresh water and the grains are gently stirred to remove protein deposits from the surface of each grain. Pour the contents into a strainer to drain the water and recover the washed grains. Gently pat-dry the grains by placing the grains on a sheet of paper or cotton toweling. Finally, place the grains between two sheets of thin cloth or paper toweling. Keep in a warm spot with good ventilation and dry at room temperature.
The grains should be dried until they become hard and yellow in colour. This may take between one to five days, depending on temperature, humidity and size of the grains. Dehydrated kefir grains remain viable for up to 1 to 1-1/2 years if placed in a sealed container stored in the fridge [do not freeze]. I recommend adding *dry milk powder, adding enough to cover the grains, which will aid in preserving the dehydrated kefir grains more effectively.
Dehydrated kefir grains can be placed in a ziplock plastic bag, ready for postage.
*Any form of dry milk powder may be used i.e. full-cream or non fat, cow or goat's milk etc.
Instructions for dehydrating Water Kefir Grains
Dehydrate an amount of water kefir grains, by first rinsing the grains with fresh clean cold water. Place the grains on a sheet of white cotton or linen toweling and leave to dry in a well ventilated area. The grains should shrink to app 1/2 the original size and have the texture and appearance of large sugar crystals. Dehydration should take between 1 to 3 days, depending on size of the grains, temperature and humidity. The grains should remain viable in a dehydrated state, for at least 6 months.
CULTURING KEFIR GRAINS SHIPPED IN FRESH FORM
For culturing both milk-based and water-based kefir grains
Pour the contents of the bottle into a strainer and strain to separate the grains from the liquid [whey, milk or sugar-water media]. Discard the strained solution then follow the directions for culturing milk-kefir explained on the web here:
http://users.chariot.net.au/~dna/Makekefir.html#Utensils
or below regarding directions for preparing water-kefir on the web:
http://users.chariot.net.au/~dna/Makekefir.html#Kefir-d-acqua
Alternatively directions explained below may be followed regarding culturing water-kefir [under "Activating dehydrated water kefir grains"]
ACTIVATION OF PARTIAL OR FULLY DEHYDRATED MILK-KEFIR GRAINS
Place the grains in one cup of fresh milk and leave in a partially sealed jar, for 24 hour at room temperature. Strain and renew the milk daily, whether or not the milk coagulates. Anywhere within four to seven days, the 24 hour batches of kefir should begin to smell sour but clean and the milk should start to coagulate within 24 hours.
NOTES: When activating dehydrated milk-based kefir grains, for the first few days the culture-product may go through some unusual stages regarding producing an unusual aroma and appearance. An overgrowth of yeast is likely to occur during the first 3 - 4 batches. This may be evident as a layer of froth or foam forming on the surface of the milk. This should settle down as consecutive batches are prepared. This foaming is mostly due to initial friendly yeast overgrowth. Within 5 - 7 days, the yeast and bacterial components should find a workable and desirable balance between the two components, to produce a kefir without excess yeast activity. When the kefir begins to have a clean sour smell, with an aroma resembling fresh yeast [or beer-like], the grains have then reached a workable or desirable state of balance. From this point on, the kefir may be consumed for its appealing flavour and consistency.
Under some circumstances, activation period may take anywhere between 2 to 4 weeks. So perseverance with a little patience is required during this period. The grains should commence growth within 3 to 4 weeks. Within this time frame the grains should become white and slimy [the slime factor of propagable kefir grains], which is an indication that the grains have begun to grow. After the fifth week, any yellow or pinkish-brown grains should be removed and discarded. This should provide enough time for any slow to activate grains, a chance to awaken and begin propagation.
Please read FAQ 38 for further details regarding reactivating dehydrated milk-kefir grains, explained on the web here:
http://users.chariot.net.au/~dna/kefir-faq.html#reactivation
ACTIVATING DEHYDRATED WATER-KEFIR GRAINS
In an 8-cup glass jar, dissolve 4 to 6 tbs of cane sugar in 4 cups of cold fresh water. Add 2 to 3 thin slices of lemon and add the dehydrated water kefir grains. Place a tight lid on the jar and let sit at room temperature for 3 to 4 days, or until the solution is bubbly with a slightly sweet flavour. If too sweet let sit for 24 hours or longer. Strain the brew, rinse the grains with cold water and repeat the process for the next batch.
NOTES: The grains should commence propagation within the first week. As consecutive batches are cultured, the beverage should be ready within 48 hours thereafter. The grains should be reasonably clear and translucent. If the grains appear to begin to go brown and loose transparency, and reduce in over size [of each grain], rinse the grains well under a stream of cold tap water, then place the grains in a sugar-solution explained above. Then store the jar in the fridge for 5 to 7 days. Strain, rinse the grains with cold water and commence brewing at room temperature once again. Dry fruit such as one dry fig or dry sultanas or raisins etc., may be included after the first week. Slices of fresh apple, straw berries including a variety of fresh fruits may substituted or included with lemon.
Kefir_making FAQs
Getting Started...
Q. What is kefir
Q. What is *real* kefir?
Q. What are kefir grains?
Q. Where did kefir grains originate?
Q. Why should I drink Kefir? Is it healthy?
Q. Where can I get some kefir grains?
Q. OK, I have some kefir grains, so how do I prepare kefir?
… and a Little More Info, PleaseQ. Should I sterilise all utensils?
Q. Should I rinse the grains with water between each milk change?
Q. I’ve never had kefir. What do I need to know beforehand?
Q. How much kefir can one drink?
Q. Is it true that the grains grow?
Q. Is it true that people eat the grains?
Q. Any tips on handling grains?
Q. What do I do if the grains become contaminated or pink spots appear on the surface of the cultured medium?
Q. I have problems drinking milk. What can I do to have kefir?
Q. Can I make kefir with non-dairy milk... e.g., soy milk?
Kefir d'acqua (Water Kefir)Q. What is kefir d'acqua?
Q. How do you make kefir d'acqua?
Q. Can I make water kefir using ordinary milk-based grains?
Q. Is it necessary to add all that sugar to kefir d’acqua? And what is the dried fruit for?
Q. What about kefir made with grape juice or other fruit juice?
Q. Are there any precautions to take when making kefir d'acqua?
Extra StuffQ. Are there other kefir recipes?
Q. How do you prepare kefir leban [fresh kefir sour cream cheese]?
Q. Can I use the whey left over from making fresh kefir cheese?
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Q. What is kefir?
A. Kefir is a health promoting fermented dairy drink, similar to yoghurt but slightly tangier. While yoghurt usually contains only two or three strains of bacteria, kefir contains a much wider variety of friendly micro organisms, including beneficial yeasts, some of which can break down lactose [milk sugar].
More detail about what kefir is:
http://users.chariot.net.au/~dna/kefirpage.html#what's-kefir
Also, please see further down the page:
http://users.chariot.net.au/~dna/kefirpage.html#kefirnovice
Q. What is *real* kefir?
A. *Real* kefir is kefir prepared in the traditional fashion, starting off with kefir grains. Store bought kefir, on the other hand, is produced by culturing pasteurised milk with a limited number and species of organisms, which are strategically selected to imitate the flavour and texture of the real thing, but with limited properties. In particular, commercial kefir cannot be used to make new kefir on a continuous basis, because the culture inevitably loses viability. Kefir grains, instead, can continue to produce fresh kefir on an indefinite basis. Also, distinctive scientifically proved therapeutic properties of the actual kefir grains, when ingested, which enhance health, are not possible with the use of commercial kefir or a kefir prepared with commercial starter-cultures.
For more information, please see Dom's Kefir in-site:
http://users.chariot.net.au/~dna/kefirpage.html#real-kefir
Q. What are kefir grains?
A. Kefir grains are a biological mass synthesized [created] by colonies of micro organisms living together [symbiotically] to form a polysaccharide mass, which form into lumps similar in appearance to cauliflower rosettes. Grain size varies from the size of wheat kernels to that of a golf ball or larger. Once placed in fresh milk, the grains [also referred to as a natural starter-culture or starter-culture], transform the milk into kefir within app. 24 hours. The same grains (or culture) are used for the next batch, to continue the ongoing process.
Q. Where did kefir grains originate?
The grains originated in the Northern Caucasus Mountain region, where local people have been using the culture for centuries - perhaps for up to one and half to two thousand years. It is said that the people of this region were gifted kefir grains from Allah, or God. At the beginning of the 20th century, Russian nobel prize winner E. Mechnikov investigated the grain's health promoting properties. This initially brought much interest in the product to the people of former USSR, which followed on to the the rest of the world.
More info available here:
http://users.chariot.net.au/~dna/kefirpage.html#Kefir-history
Q. Why should I drink Kefir? Is it healthy?
Kefir has many health promoting benefits. In a nutshell, these benefits could be divided in two groups:
1. Kefir grains contain a vast amount of micro-organisms from 4 genus groups, including lactic acid bacteria and yeasts. The distinctive microflora of kefir is compatible with the needs of our body. Kefir micro-organisms are able to stabilize or balance the Gastro Intestinal tract, as well as ensuring better digestion and fight off harmful bacteria, yeasts [including those which cause stomach ulcers, diarrhea, and yeast infection] and viruses. The consumption of kefir has proven to stimulate the immune system, which can also assist the cells of the body to increase the production of interferon [virus controlling agent] due to a unique lipid [sphingomyelin] found in kefir.
2. Kefir may provide other benefits: the friendly micro-organisms breakdown substances such as lactose in milk and from, this synthesize favourable substances, including lactic acid and "Kefiran", a health promoting polysaccharide unique to kefir grains and to kefir. Kefiran has proven to reduce the size of certain cancers, including having anti-inflammatory properties. Certain organisms of kefir produce lactase, an enzyme which breaks down lactose [milk sugar], which provides the body the ability to further breakdown any milk-sugar [lactose] in the diet, while taking kefir with that meal.
Q. Where can I get some kefir grains?
A. You can post a request for kefir grains to the list. Please be sure to mention the country, town or area which you live in so that members on the list can respond accordingly. Also, please check Clarkson database at : http://66.46.11.99/clarkson/Show/Clarkson/kefir/default.asp for a source of kefir grains in your area. This database lists many individuals around the world who are willing to share kefir grains.
You may also try to procure kefir grains from the list owner Dom, if he has spare culture. Dom provides a copy of his book along with the culture and although he resides in Australia, he provides two options for procuring his quality kefir grains. He can send fresh kefir grains [which come with a portion of dehydrated kefir grains as a generous offer and as a back up supply for your convenience] worldwide. He also provides an option to obtain just dehydrated kefir grains, at an affordable price. Please email Dom for details state your country of residence so that appropriate details regarding cost are forwarded to you. Dom's email address:
dna@chariot.net.au
Alternatively, it might be possible to post an announcement at your local nature or health food shop, i.e. if a public bulletin board is available.
Q. OK, I have some kefir grains, so how do I prepare kefir?
A. Basically, just put two to three tablespoons of kefir grains in a half litre [1 pint] of fresh milk, and leave at room temperature for 24 hours. For greater or smaller quantities, vary the proportions accordingly. Unlike yoghurt, the milk with the added culture does not need to be heated and kept warm during incubation. Nor does it need to be boiled first [to sterilize or pasteurize]. Actually, brewing at a cooler temperature makes a smoother kefir [but takes a little longer to brew]. Once the kefir is ready, strain through a plastic colander or sieve and plop the grains into more fresh milk to prepare the next batch. This process is simply repeated.
For more details, including tips on handling utensils etc. please go to this webpage:
http://users.chariot.net.au/~dna/Makekefir.html
Q. Should I sterilise all utensils?
A. While cleanliness is always important in the kitchen, it is not necessary to go as far as to maintain a sterile environment when preparing kefir, since kefir grains are hardy and survive quite well in the kitchen environment. However, try avoiding non-stainless steel metal utensils, because the acidity of the kefir may cause corrosion. To avoid problems, you could opt to use only glass, plastic, nylon or wooden utensils.
Q. Should I rinse the grains with water between each milk change?
A. This is not necessary. But if you really want to, you can “fast” the grains by placing them in filtered water for one day [one part kefir grains to 3 part water as a general rule]. The grains are then strained and placed directly in fresh milk to prepare kefir as per usual [explained above]. This can be performed once weekly, fortnightly or monthly. The water strained from soaking the grains contains Kefiran, a unique healthy polysaccharide native to kefir grains. Dom, the list owner has given a uniquie name for this solution “Kefiraride”, which has a variety of applications.
For more information regarding rinsing:
http://users.chariot.net.au/~dna/kefir-faq.html#rinsing
Tips for using Kefiraride:
http://users.chariot.net.au/~dna/kefir-faq.html#kefiraride
Q. I’ve never had kefir. What do I need to know beforehand?
A. Certain individuals may have a reaction when first consuming kefir, similar to the Herxheimer reaction. This reaction may range from slight stomach cramps to diarrhea, nausea or vomiting – which may be attributed to certain changes of the intestinal microflora due to the new micro-organisms and unique substances introduced through drinking kefir. In most cases, individuals find that symptoms eventually clear up after a short period of time. Newcomers to kefir who may experience such reactions should begin taking lesser amounts of kefir, for instance, taking a couple of tablespoons of kefir daily, and increasing the amount by one to two tablespoons each day, until one cup of kefir can be well tolerated. Once this amount is well tolerated, in most cases, the individual can then take one to four or more cups of kefir daily, if required.
Q. How much kefir can one drink?
A. As much as you feels comfortable with. Many individuals may have one cup of kefir in the morning and one at night before bed time. Some individuals enjoy a small glass of kefir before each meal. One word of caution: like yoghurt, kefir contains lactic acid bacteria which can erode the tooth enamel, so be sure to rinse your mouth with water after consuming kefir, or after consuming food which contains lactic or acetic acid.
Q. Is it true that the grains grow?
A. Yes, healthy kefir grains should grow by 5 to 15 % daily [by weight]. This enables generous people to share extra grains with others who are interested in the preparing the drink fro themselves. For additional tips on what to do with growing grains, please check out:
http://users.chariot.net.au/~dna/kefir-faq.html#growthrate
Q. Is it true that people eat the grains?
A. Yes! Grains contain many beneficial properties. A Japanese study showed that among mice that had been inoculated with cancer and later fed with kefir grains, cancer growth stopped and even receded. For further details including recipes, check out:
http://users.chariot.net.au/~dna/kefir-faq.html#ingestingkg
Q. Any tips on handling grains?
A. Avoid exposing them to excessive temperatures, since some of the micro-organisms are quite sensitive to heating above body temperature. As a rule of thumb, milk that is too hot for you to put a finger in it, will surely kill your grains.
Q. What do I do if the grains become contaminated or pink spots appear on the surface of the cultured medium?
A. This might happen especially if you covered the jar with a cloth, which might favour certain mold spores or weed micro-organisms to fall in the kefir. Simply strain the grains and rinse them in filtered water. “Fast” them in plain water for 24 hours in the fridge. Rinse the grains with fresh water and place them in fresh milk. You might want to discard the first batch of kefir, since it might still taste unusual. The second batch of kefir should be good enough to drink.
Q. I have problems drinking milk. What can I do to have kefir?
A. Either:
- you are lactose intolerant: in that case, leave your kefir to ripen one more day before drinking it. This will give time for the kefir bugs to digest more of the lactose [milk sugar] in the milk, and for the bugs to produce more lactase [the enzyme responsible for breaking down lactose which your body can then utilise to further break down lactose]. For more info:
http://users.chariot.net.au/~dna/Makekefir.html#Storing
OR
- you are allergic to casein (the protein in milk). In such cases you might try different milks (goat's and sheep's milk is less allergenic than cow's milk), or you may have to avoid dairy altogether, in which case you should read the next question.
Q. Can I make kefir with non-dairy milk... e.g., soy milk?
A. Yes, with some adjustment, you can use just about any non-dairy milk. The only drawback is that the grains will not be able to grow any longer, because they need their native dairy medium to grow. For more details on non-dairy kefir, please check out Dom’s alternative dairy milk kefir page:
http://users.chariot.net.au/~dna/vegmilk.html
Q. What is kefir d'acqua?
A. It's Italian for water kefir [in
For more information on water kefir and the unique kefir grains to produce the beverage, please check out:
http://users.chariot.net.au/~dna/kefirpage.html#alternativekefir
Q. How do you make kefir d'acqua?
A. Water kefir is made by adding sugar, lemon juice and a dried fig/plum/date/apricot etc. to water and special crystal-like water kefir grains, which are quite different than milk kefir grains.
For more information on how to prepare water kefir:
http://users.chariot.net.au/~dna/Makekefir.html#Kefir-d-acqua
For more information regarding sugary water kefir-grains:
http://users.chariot.net.au/~dna/kefirpage.html#alternativekefir
Q. Can I make water kefir using ordinary milk-based grains?
A. Water kefir can be prepared with milk kefir-grains. Use only a portion or extra milk-grains for this. First rinse the grains with filtered cold water and place them in a 5 to 10 % sugar solution. Add some lemon slices and brew for 48 hours at room temperature. Initially, the grains will take up to 4 days to begin brewing the new form of kefir. This is normal since they have to get used to the new medium. Please note that once converted to water, milk grains will stop growing and will no longer be able to produce milk kefir any more. So make sure to only use extra grains to make the water version, and always brew the two types separate from each other.
Q. Is it necessary to add all that sugar to kefir d’acqua? And what is the dried fruit for?
A. If using milk kefir grains transferred to a water media, then it is suggested to feed the grains with a variety of different sugars. This helps maintain a diversified microflora in the kefir. Instead of dried fruit, you can add fresh fruit. The lemon keeps the solution slightly acidic and produces a lemonade-like flavour. Different fresh fruits will produce water kefir, which retains the flavour of that fruit.
Q. What about kefir made with grape juice or other fruit juice?
A. Detailed instructions here:
http://users.chariot.net.au/~dna/Makekefir.html#Grape-juice_Kefir
and
http://users.chariot.net.au/~dna/kefir-faq.html#addfruitjuice
Q. Are there any precautions to take when making kefir d'acqua?
A. Yes, there are two things that one must be aware of:
1. Kefir d'acqua is a fizzy drink. If you brew it in a tightly sealed jar, pressure will build up pretty fast. It is important to use a strong enough vessel to withstand the pressure, but especially to leave plenty of room in the jar for the gas to accumulate. Typically, you should leave your jar half full with the kefir ingredients.
2. Kefir d'acqua is a mild alcoholic drink - it may contain between 0.5 to 3 % alcohol per volume [depending on the amount of sugar and fermentation time]. So it might not be advisable to give to small children, or animals, and one should be careful when driving a car to avoid accidents.
Q. Are there other kefir recipes?
A. You can make kefirkraut [fermented cabbage, a bit like sauerkraut], several kinds of cheese (see next FAQ), and pizza/bread dough. On the sweet side, smoothies and desserts may be enjoyed with the addition of kefir. This group has a recipe section (go the group’s web site http://groups.yahoo.com/group/Kefir_making and look under “Database”). Check this database periodically as people add their successful recipes and experiments.
Instructions for kefirkraut:
http://users.chariot.net.au/~dna/kefirkraut.html
Some recipes with milk kefir:
http://users.chariot.net.au/~dna/Makekefir.html#the-butterfly
Q. How do you prepare kefir leban [fresh kefir sour cream cheese]
A. Please visit Dom's kefir-cheese site regarding recipes for preparing fresh cheeses with kefir.
Study of Stability and Properties of Kefiran and Succinyl Kefiran for Application to Cosmetics and Foods
Takahiro Mitsue a), Yusaku Fujio b)
a) Sansho Seiyaku Co., Ltd.
b) Faculty of Agriculture, Kyushu University
Keywords: Kefir, Kefiran, Succinyl Kefiran, Cosmetics, Foods
Abstract
Kefir is a popular fermented milk produced by a starter, the so-called Kefir grains, in
the Caucasus region of Russia. Kefiran contained in Kefir is a polysaccharide with a
repeating unit of Glc-Gal-(-Glc)-Gal-Gal-Glc, and its molecular weight is 1,000-4,000
kDa. Lactobacillus kefiranofaciens KF-75 isolated from the Kefir grains was improved
to yield an industrial Kefiran production of 2 kg per day of purified Kefiran, at present.
An aqueous solution of 1%(w/v) Kefiran was gelatinized automatically by standing at
low temperature (5 ºC). In contrast, Kefiran chemically modified by acylation, which
was Succinyl Kefiran, did not gelatinize under at low temperature (5 ºC), nor aqueous
solution of 1%(w/v) Succinyl Kefiran in 40%(v/v) ethanol concentration. Because of the
high viscosity (60mPa•s, at 20 ºC) of 1%(w/v) Succinyl Kefiran aqueous solution (pH6.5),
showed useful properties, both as a beverage ingredient for adding viscous accretion
property, and as a cosmetic ingredient for human skin for giving moisture and good
feeling accretion properties.
a) Sansho Seiyaku Co., Ltd.
b) Faculty of Agriculture, Kyushu University
Keywords: Kefir, Kefiran, Succinyl Kefiran, Cosmetics, Foods
Abstract
Kefir is a popular fermented milk produced by a starter, the so-called Kefir grains, in
the Caucasus region of Russia. Kefiran contained in Kefir is a polysaccharide with a
repeating unit of Glc-Gal-(-Glc)-Gal-Gal-Glc, and its molecular weight is 1,000-4,000
kDa. Lactobacillus kefiranofaciens KF-75 isolated from the Kefir grains was improved
to yield an industrial Kefiran production of 2 kg per day of purified Kefiran, at present.
An aqueous solution of 1%(w/v) Kefiran was gelatinized automatically by standing at
low temperature (5 ºC). In contrast, Kefiran chemically modified by acylation, which
was Succinyl Kefiran, did not gelatinize under at low temperature (5 ºC), nor aqueous
solution of 1%(w/v) Succinyl Kefiran in 40%(v/v) ethanol concentration. Because of the
high viscosity (60mPa•s, at 20 ºC) of 1%(w/v) Succinyl Kefiran aqueous solution (pH6.5),
showed useful properties, both as a beverage ingredient for adding viscous accretion
property, and as a cosmetic ingredient for human skin for giving moisture and good
feeling accretion properties.
Effect of the kefir ferment on the colibacteria during the process of *kefir* *production* [*Contamination* control]
Ivanova, L N
Molochn Prom-st' Sept 1975 9: 8-11.
LC: 44.8 M734
Language: Russian
Document Type: ARTICLE
Section Headings: 2010 Dairy Products (1972-79); 1505 Consumer
Protection (1972-79)
Identification of lactic acid bacteria isolated from freeze-dried kefir
grains (Georgia, Russia).
Ohara, N.; Suzuki, M.; Okada, S.; Uchimura, T.; Kozaki, M.; Komagata, K.
Fac. of Agric., Tokyo Univ. of Agric., 1-1-1 Sakuragaoka, Setagayu-ku,
Tokyo 156, Japan
Japanese Journal of Food Microbiology 1997 , 13 (4) 165-171
NOTE: 29 ref.
DOCUMENT TYPE: Journal Article ISSN: 0910-8637
LANGUAGE: Japanese SUMMARY LANGUAGE: English
Lactic acid bacteria (n = 6) isolated from freeze-dried kefir grains from
Georgia were identified and the flora compared with that previously
obtained from kefir grains. Based on phenotypic characteristics and DNA-DNA
relatedness, the isolates were identified as Weisella confusa (GKL1),
Lactobacillus kefir (GKL2) and Lactobacillus kefiranofaciens (GKL5, GKL7,
GKL9, GKL28). However, results of phenotypic characterization indicated
that GKL5 and GKL7 might be Lactobacillus acidophilus whilst GKL9 might be
Lactobacillus delbrueckii subsp. lactis. The predominant species was W.
confusa and it is thought that it may have *contaminated* kefir during
activation of the freeze-dried *kefir* *grains*. Lactococcus lactis and
Leuconostoc mesenteroides, isolated previously from kefir grains, were not
detected in Georgian kefir grains; it is suggeted that their absence may be
due to culture conditions prior to freeze drying. (From En summ.)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Microflora present in kefir grains of the Galician region (North-West of
Spain).
Angulo, L.; Lopez, E.; Lema, C.
Microbiol., Fac. de Ciencias, Univ. de Vigo, Apartado 874, 36200 Vigo,
Spain
Journal of Dairy Research 1993 , 60 (2) 263-267
NOTE: 10 ref.
DOCUMENT TYPE: Journal Article ISSN: 0022-0299
LANGUAGE: English
Microflora present in kefir grains (a symbiotic association of yeasts and
lactic acid bacteria embedded in a polysaccharide matrix (kefiran) used in
the fermentation of milk was investigated. 8 kefir grains were obtained
from different dairies in Galicia, Spain; grains were propagated by twice-
or thrice-weekly transfer into pasteurized cows' milk. From the interior of
kefir grains, 49 yeast strains corresponding to 5 genera were isolated;
Torulaspora delbrueckii and Saccharomyces cerevisiae were 13.3 and 10.6%,
respectively, of the total yeast spp. isolated. 46 strains of lactic acid
bacteria representing 4 genera were isolated; 9 homofermentative (25.7%)
and heterofermentative (74.3%) lactobacilli spp. were identified.
Lactococcus lactis subsp. lactis (6.2%) was isolated from most *kefir*
*grains*. Also, 18 bacterial strains, considered to be *contaminating*,
representing 5 genera were isolated, including spp. of the Pediococcus,
Micrococcus, Bacillus and Acetobacter genera. (JAT)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Survival of Listeria monocytogenes in fermented milk products.
AUTHOR: Stanczak Bozenna J(a); Szczawinski Jacek; Peconek Janina
AUTHOR ADDRESS: (a)ul. Nowoursynowska 166, 02-787 Warszawa, Poland
JOURNAL: Medycyna Weterynaryjna 53 (10):p592-595 1997
ISSN: 0025-8628
RECORD TYPE: Abstract
LANGUAGE: Polish; Non-English
SUMMARY LANGUAGE: English
ABSTRACT: Samples of fermented milk products on the Polish market called
"natural yogurt" and "natural kefir" as well as raw milk were
artificially *contaminated* with L. monocytogenes (inoculum 10-6
cells/ml). Yogurt and kefir were stored at 6 degree C for 35 days and at
20 degree C for 14 days. Samples of raw milk were incubated at 20 degree
C for 7 days. In each sample the pH-value, aerobic plate count and number
of listeria were determined. It was found that the number of L.
monocytogenes decreased in all tested products during storage. From the
regression analysis T-4D values (time required for reduction of listeria
by 4 log units) were calculated. T-4D values amounted to: for kefir and
yogurt stored at 6 degree C - 43.4 and 25.4 days respectively; for kefir
and yogurt stored at 20 degree C - 9.5 and 4.8 days, for raw milk stored
for natural fermentation at 20 degree C - 38.2 days. The obtained results
were compared to theoretical results obtained from the Pathogen Modeling
Program 4.0. This program makes it possible to predict the behavior of L.
monocytogenes in culture media. It was found that microflora of fermented
milk products increases the dying rate of L. monocytogenes during storage
at 20 degree C. Lactic acid bacteria used for yogurt production seem to
exert a particularly strong antagonistic effect on L. monocytogenes.
REGISTRY NUMBERS: 50-21-5: LACTIC ACID
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fate of aflatoxin M1 during kefir processing and its effect on the
microflora and the chemical structure.
Ismail, A. A.; Tawfek, N. F.; Abd-Alla, E. A. M.; El-Dairouty, R. K.;
Sharaf, O. M.
Food Technol. & Dairying Lab., Natn. Res. Cent., Dokki, Cairo, Egypt.
Deutsche Lebensmittel-Rundschau vol. 85 (3): p.76-78
Publication Year: 1989
ISSN: 0012-0413
Language: English Summary Language: german
Document Type: Journal article
Kefir manufactured using kefir grain and fresh skim milk was spiked with
2.0 and 4.5 micro g/litre aflatoxin M1 (AFM1). Treatment of milk with
low-heat (64 deg C for 20 min) and high-heat pasteurization (84 deg C for
30 min) reduced AFM1 content to 58 and 62%, respectively, with low levels
of AFM1 and to 53 and 57%, respectively, with high concn of AFM1. No
difference in microbial content was observed between the control and the
*contaminated* milk. Acetaldehyde content ranged from 4.0 to 25.3 micro
M/ml. The pH was 4.0-4.3. Total solids content varied from 6.7 to 9.05%.
It is concluded that AFM1, if present in milk used to manufacture cultured
dairy products, will remain in the products after processing. 17 ref.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Behavior of aflatoxin M1 in yogurt, buttermilk and kefir.
Wiseman, D. W.; Marth, E. H.
Dep. Food Sci., Wisconsin Univ., Madison, Wis. 53706, USA.
Journal of Food Protection vol. 46 (2): p.115-118
Publication Year: 1983
ISSN: 0363-028X
4 fig., 3 tab.
Language: English
Document Type: Journal article
Yoghurt, buttermilk and kefir were made from milk that was naturally
*contaminated* with aflatoxin M1. The aflatoxin content of yoghurt varied
during storage, but after 6 weeks at 7 deg C it was essentially at the
same levels as in the initial milk. In 3 buttermilk samples the aflatoxin
M1 content increased after fermentation and the content remained high for
4 days of storage at 7 deg C. Three further buttermilk samples behaved
like the yoghurt, the aflatoxin M1 content was variable during holding,
but remained stable through 2 weeks of storage at 7 deg C. Kefir was made
from skim milk subjected to low-heat (64 deg C for 30 min.) or high-heat
pasteurization (84 deg C for 30 min.). After fermentation, the aflatoxin
M1 content of kefir decreased. During storage the aflatoxin M1 content of
3 of 4 kefir samples increased slightly, but in no instance did it return
to original levels during or at the end of storage at 7 deg C. 16 ref.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Qualitative and quantitative analyses of kefir.
Original Title: Le Kefir: analyse qualitative et quantitative.
Vayssier, Y.
Lab. de Microbiol., Univ. de Clermont-Ferrand II, 4 Rue Ledru, 63000
Clermont-Ferrand, France.
Revue Laitiere Francaise (No. 361): p.73-75
Publication Year: 1978
ISSN: 0035-3590
Language: French Summary Language: english
Document Type: Journal article
Analysis of 2 samples of kefir grains from the Vienne region of France,
4 kefir starters (from Germany, Holland, Canada and Poland) and 2 kefir
beverages (from Germany and Czechoslovakia) showed that they varied
greatly in microbial composition. The 2 samples of kefir grains had
similar contents of lactic acid bacteria and yeasts, but one contained
appreciable amounts of coliforms and the other had a high content of
faecal streptococci. The German and Canadian starters contained 2 X 107
and 8 X 106 faecal streptococci/g resp., and the Polish starter contained
no yeasts. The kefir beverage from Czechoslovakia was *contaminated* with
4 X 104 moulds/ml. The proportion of lactobacilli in the kefir lactic
flora varied from 0 in the Polish starter to 100% in the Dutch starter and
German beverage. Streptococcus lactis, Str. diacetilactis, Leoconostoc
cremoris, Leuc. mesenteroides, Lactobacillus casei subsp. alactosus, L.
casei subsp. rhamnosus, L. brevis, L. cellobiosus and L. helveticus subsp.
jugurti were identified in the lactic flora of the different samples; the
yeasts were mainly Saccharomyces florentinus and Sacch. globosus in the
kefir grains and starters, and Kluyveromyces bulgaricus and K. fragilis in
the beverages. For production of kefir in France, the development of a
pure kefir starter with standardized microbial composition is necessary.
21 ref.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bacteriological evaluation of kefir.
Bugrova, V. I.; Bursak, G. Z.; Rudykh, K. I.; Muzyukina, T. M.;
Fel'dberg, F. L.; Shlyakhova, V. V.; Zhelikhovskaya, F. M.
Moskovskii Nauchno-issled. Inst. Gigieny imeni F. F. Erismana, Moscow,
USSR
Gigiena i Sanitariya 1969 , 34 (7) 91-92
DOCUMENT TYPE: Journal Article
LANGUAGE: Russian
578 samples of kefir were examined bacteriologically in the Moscow,
Irkutsk, Tula, Stavropol' and Kuibyshev dairy factories. 436 had a coliform
titre (by the standard method GOST 9225-59) of LESS THAN 0.3, 59 a titre
of 0.3, 16 a titre of 3 and 67 a titre of GREATER THAN 3. Numbers of
samples showing citrate-positive and citrate-negative coliform titres
respectively were: LESS THAN 0.3, 261 and 281; 0.3, 158 and 150; 3, 48 and
36, GREATER THAN 3, 111 and 111. The large proportion of samples with
coliform titre LESS THAN 0.3 was taken as indicating unsatisfactory
sanitary conditions of manufacture. Results of bacteriological examinations
at different stages of manufacture in the different factories are outlined
and cuases of *contamination* described. A coliform titre of GREATER THAN
OR EQUAL 3 is suggested as standard ffor bacteriological evaluation of
kefir. On direct microscopy, lactic acid streptococci and yeast cells
should always be detected.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Changes in the nitrate content of yogurt and kefir.
Steinka, I.; Przygylowski, P.
Przemysl Spozywczy 47 (10) 281-282 91993) [15 ref. Pl, eng] [Katedra Towaroznawstwa i
Ladunkoznawstwa, WSM, 81-192 Gdynia, Poland]
To detirmine changes occurring in the nitrate contents of yogurt and kefir during their manufacture
and ripening, 0.7% fat instant milk [antibiotic-free] was reconstituted to 10% DM, pasteurized (95
C/30 min), cooled, inoculated with 4-5% yogurt starter or 3% kefir starter, treated with sufficient
KNO3 to provide 5, 10 or 15 mg NP3 -/dm3, and incubated at 42 C for 4 hours (yogurt) or 23
C for 22 h (kefir). Yogurt was stored initially at 4-6 C for 12 h and both end products were stored
at 4-6 C for 12 h. Analyses covered acidity (SH) and nitrate contents of the pasteurized raw
material, curd, ripening yogurt and both products after 24 h of storage. In yogurt, NO3 - formation
remained steady during curd formation, fell in the aqueous phase during ripening (by 2.90-3.71
mg/dm3), and returned to the initial level after 24 h at 4-6 C. In kefir, NO3- content declined in the
aqueous phase by an average of 3.7 mg/dm3 during storage. It is concluded that changes in NO3 -
concentration of the 2 products were dependent not on level in the raw material, but on temp and
rate of acidification of milk; addition of 5-15 mg NO3 -dm3 had no effect on the lactic fermentation
process.
Kefir – a complex probiotic
......................................................................................................................................................................
Kefir – a complex probiotic
Edward R. Farnworth
Food Research and Development Centre, Agriculture and Agri-food Canada, St. Hyacinthe, Quebec, Canada J2S 8E3.
Tel. 450-773-1105. Fax 450-8461. E-mail farnworthed@agr.gc.ca
Abstract
Kefir is a fermented milk drink produced by the actions of bacteria and yeasts contained in kefir grains, and
is reported to have a unique taste and unique properties. During fermentation, peptides and exopolysacchar-
ides are formed that have been shown to have bioactive properties. Moreover, in vitro and animal trials have
shown kefir and its constituents to have anticarcinogenic, antimutagenic, antiviral and antifungal properties.
Although kefir has been produced and consumed in Eastern Europe for a long period of time, few clinical
trials are found in the scientific literature to support the health claims attributed to kefir. The large number of
microorganisms in kefir, the variety of possible bioactive compounds that could be formed during fermenta-
tion, and the long list of reputed benefits of eating kefir make this fermented dairy product a complex
probiotic.
Keywords: kefir, probiotics, kefir grains, kefiran, human health, bioactive ingredients
known than yoghurt; however, an analysis of its composi-
1. Introduction
tion indicates that it may contain bioactive ingredients that
Archaeological evidence has indicated that the process of give it unique health benefits, which means that kefir may
fermentation in foods was discovered accidentally thou- be an important probiotic product (Farnworth 1999).
sands of years ago. However, over time, it soon became
apparent that many fermented foods had longer storage
2. Origins of kefir
lives and improved nutritional values compared to their
Kefir is a viscous, slightly carbonated dairy beverage that
unfermented equivalents, making this form of food proces-
contains small quantities of alcohol and, like yoghurt, is
sing a popular technique. It is not surprising, therefore, to
believed to have its origins in the Caucasian mountains of
find that many foods including vegetables, fruits, cereals,
the former USSR. It is also manufactured under a variety
meat and fish have all been converted into desirable food
of names including kephir, kiaphur, kefer, knapon, kepi
products by fermentation and are still being consumed
and kippi (Koroleva 1988a), with artisanal production of
throughout the world today (Farnworth 2004).
kefir occurring in countries as widespread as Argentina,
Certain bacteria, either alone or through the changes
Taiwan, Portugal, Turkey and France (Thompson et al.
they bring about during fermentation, have been shown to
1990; Angulo et al. 1993; Lin et al. 1999; Garrote et al.
have positive effects on health as well as resistance to dis-
2001; Santos et al. 2003; Gulmez and Guven 2003). It is
ease. Interest in such probiotic species has increased in
not clear whether all kefirs originate from a single original
recent years as more is learned about the microorganisms
starter culture, since microbial analyses of kefir samples
used in the fermentation process, and the possibility of
taken from different locations indicate microflora popula-
adding beneficial bacteria to food products. Furthermore,
tion differences.
consumers are increasingly looking to improve their health
The FAO/WHO (2001) have proposed a definition of
and increase their resistance to disease through dietary
kefir based on the microbial composition of both kefir
means.
grains (the starter culture used to produce kefir) and the
Fermented dairy products from milk from a variety of
final kefir product (see Table 1).
animals are perhaps the most common fermented foods
worldwide. Yoghurt, which is known by many different
names in different countries, is a fermented product which 3. Kefir manufacture
is familiar to consumers. Kefir, meanwhile, is less well
Although commercial kefir is traditionally manufactured
from cows’ milk, it has also been made from the milk of
Food Science and Technology Bulletin: Functional Foods 2 (1) 1–17
ewes, goats and buffalos. Moreover, kefir produced using
DOI: 10.1616/1476-2137.13938. Published 4 April 2005
ISSN 1476-2137 # IFIS Publishing 2005. All Rights Reserved soy milk has also been recently reported (Ismail et al.
Kefir – a complex probiotic E.R. Farnworth
2
lactic acid production and ethanol production, compared
Table 1. Codex Alimentarius description of kefir*
to kefir produced from soy milk alone (Liu and Lin 2000).
Definition
The grains used in this study were found to have a-galac-
Starter culture prepared from kefir grains, Lactobacillus kefiri, tosidase activity that helped explain how these kefir grains
and species of the genera Leuconostoc, Lactococcus and
were able to use the galactose-based carbohydrates which
Acetobacter growing in a strong specific relationship. Kefir
occur in soy milk.
grains constitute both lactose-fermenting yeasts (Kluyveromyces
Kefir grains are key to kefir production, and it has been
marxianus) and non-lactose-fermenting yeasts (Saccharomyces
unisporus, Saccharomyces cerevisiae and Saccharomyces found that the finished product has a different microbiolo-
exiguus). gical profile from the grains and therefore cannot be used
to inoculate a new batch of milk (Simova et al. 2002).
Composition
Grains have been shown to possess a dynamic and com-
Milk protein (% w/w) min. 2.8
plex flora which is not conducive to commercial produc-
<10
Milk fat (% m/m)
tion of a uniform, stable product; this has prompted
Titratable acidity, expressed as % of lactic acid min. 0.6
groups to try to produce kefir from a mixture of pure cul-
(% m/m)
tures (Petersson et al. 1985). Duitschaever et al. (1987,
Ethanol (% vol./w) not stated
1988a) combined a yoghurt culture with three other lactic
min. 107
Sum of specific microorganisms constituting the
acid bacteria and Saccharomyces cerevisiae (a non-lactose
starter culture (cfu/g, in total)
fermenting yeast) to produce a fermented milk with kefir
min. 104
Yeasts (cfu /g)
characteristics (which produced CO2 and contained etha-
*From Codex Standard for Fermented Milks CODEX STAN 243-2003
nol) under a variety of conditions. Rossi and Gobbetti
(1991) produced a multistarter culture using four bacteria
and two yeasts isolated from kefir grains in order to manu-
´
1983; Mann 1985; Zourari and Anifantakis 1988; Halle facture kefir under a continuous process. More recently,
et al. 1994; Kuo and Lin 1999). Traditionally, kefir is pro- Beshkova et al. (2002) produced a starter consisting of
duced by adding kefir grains (a mass of proteins, polysac- two bacteria (Lactobacillus helveticus and Lactococcus
charides, mesophilic, homofermentative and hetero- lactis subsp. lactis,) and one yeast (S. cerevisiae) isolated
fermentative lactic acid streptococci, thermophilic and from kefir grains and combined with two yoghurt strains
mesophilic lactobacilli, acetic acid bacteria, and yeast) to (Lactobacillus delbrueckii subsp. bulgaricus, and Strepto-
´
a quantity of milk (Koroleva 1982; Halle et al. 1994; coccus thermophilus). Yeast was added to the starter with
Tamime et al. 1999). The size of the initial kefir grain sucrose either at the beginning, or after lactic acid fermen-
inoculum affects the pH, viscosity and microbiological tation. The two resulting kefirs produced were found to
profile of the final product (Koroleva and Bavina 1970; have high numbers of viable cocci and lactobacilli and
Garrote et al. 1998). Koroleva (1991) reported that grain had chemical and organoleptic properties that were similar
to milk ratios of 1:30 to 1:50 were optimum. In some to traditional kefir. A commercial kefir is being produced
manufacturing procedures, a perculate of the grains from a in the United States using a mixture of defined microor-
coarse sieve is used as the mother culture to inoculate ganisms rather than kefir grains. This starter culture mix-
fresh milk. Fermentation of the milk by the inoculum pro- ture has been reported to contain Streptococcus lactis, L.
ceeds for approximately 24 hours, during which time plantarum, Streptococcus cremoris, L. casei, Streptococcus
homofermentative lactic acid streptococci grow rapidly, diacetylactis, Leuconostoc cremoris and Saccharomyces
initially causing a drop in pH. This low pH favours the florentinus (Hertzler and Clancy 2003).
growth of lactobacilli, but causes the streptococci numbers Starter cultures containing freeze-dried lactic acid bac-
to decline. The presence of yeasts in the mixture, together teria and yeasts from kefir grains are now available com-
with fermentation temperature (21–238C), encourages the mercially; some are supplemented with additional microor-
growth of aroma-producing heterofermentative strepto- ganisms to impart desirable characteristics in the finished
cocci. As fermentation proceeds, growth of lactic acid kefir product (Piotr Kolakowski, private communication).
bacteria is favoured over growth of yeasts and acetic acid It is evident that the final product, as produced from kefir
bacteria (Koroleva 1982). grains, will have a larger number and variety of microor-
Taiwanese researchers have shown that the lactic acid ganisms than kefir produced from a mixture of a small
bacteria from kefir grains grow more slowly in soy milk number of pure cultures.
compared to cows’ milk (Liu and Lin 2000). This may be Kefir is still most familiar to consumers in Eastern Eur-
due, in part, to the slower production of growth factors at ope, although commercial production now occurs in North
the beginning of fermentation when soy milk is the America. However, several patents can be found relating
substrate rather than cows’ milk. Addition of carbohydrate to commercial kefir production worldwide (Klupsch 1984;
(e.g. 1% glucose) to soy milk increases yeast numbers, Dmitrovskaya 1986; Tokumaru et al. 1987; Kabore 1992).
Kefir – a complex probiotic E.R. Farnworth 3
Production/consumption figures for kefir are not readily acceptability of kefir, compared to traditionally made kefir
(Duitschaever et al. 1991; Muir et al. 1999).
available since statistics for fermented dairy products are
not always broken down into separate items such as Acetaldehyde and acetoin have received particular
yoghurt and kefir (Mann 1989; Libudzisz and Piatkiewicz attention with regard to their roles during kefir manufac-
1990; Serova 1997; Zimovetz and Boyko 2000). A survey ture because of their contribution to taste; both have been
of kefir products purchased on the retail market in War- found to increase in concentration during kefir fermenta-
saw, Poland showed that 73% of products contained 107– tion. During storage, acetaldehyde increases in concentra-
109 cfu bacteria/g, and that 97% of samples were coli- ¨
tion and acetoin decreases (Guzel-Seydim et al. 2000a,
˘
¨
form-free (Molska et al. 2003). However, 48% of samples 2000b). Yuksekgag et al. (2004a), in their study of 21 iso-
did not meet FAO/WHO requirements for yeast numbers lates of lactic acid bacteria from various sources of Turk-
(FAO/WHO 2001). ish kefir, were able to show that all 21 isolates produced
acetaldehyde (0.88–4.40 mg/ml) when added to milk.
A whey beverage with an acceptable flavour has
4. Characteristics of kefir
recently been developed using kefir yeasts (Athanasiadis
et al. 2004), especially when fructose was added to fresh
The flavour, viscosity and microbial/chemical composition
milk before fermentation, and final pH of the beverage
of the final kefir product can be affected by the size of the
inoculum added to the milk, the occurrence of any agita- was 4.1. Fructose was found to increase production of sev-
tion during fermentation, and the rate, temperature and eral flavour volatiles, but did not increase fermentation
time.
duration of the cooling and ripening stages following fer-
mentation (Koroleva 1988b). Natural kefir has a refresh-
ing, yeasty taste and a ‘sparkling’ mouth feel (Kemp
5. Kefir grains
1984).
Kefir grains resemble small cauliflower florets: they mea-
Modern manufacturing procedures for kefir result in
sure 1–3 cm in length, are lobed, irregularly shaped, white
ethanol levels in the finished product of 0.01–0.1% (Koro-
to yellow-white in colour, and have a slimy but firm tex-
leva 1982), although kefir with ethanol concentrations as
`
ture (La Riviere et al. 1967; Kosikowski and Mistry 1997;
high as 0.25% have been produced from grains in the
laboratory (Kuo and Lin 1999; Simova et al. 2002; Besh- see Figure 1). Grains are kept viable by transferring them
kova et al. 2002). The amounts of ethanol and CO2 pro- daily into fresh milk and allowing them to grow for
duced during fermentation of kefir depend on the produc- approximately 20 hours; during this time, the grains will
´
have increased their mass by 25% (Halle et al. 1994).
tion conditions used. CO2 content of kefir has been said to
be ‘comparatively low’ in relation to other fermented Grains must be replicated in this way to retain their viabi-
drinks (Koroleva 1982); values of 0.85–1.05 g/l have been lity, since old and dried kefir grains have little or no abil-
`
ity to replicate (La Riviere et al. 1967). Kefir grains repli-
reported for kefir produced from kefir grains (Beshkova
et al. 2002; Simova et al. 2002) and 1.7 g/l for kefir pro-
duced from purified cultures (Gobbetti et al. 1990) How-
ever, the generation of CO2 during kefir manufacture,
especially after packaging, presents some practical pro-
blems, since the microorganisms (particularly yeasts) in
the kefir continue to grow following packaging. The con-
tainer used to package kefir must therefore be either strong
enough to withstand any pressure build up (e.g. glass) or
flexible enough to contain the volume of gas produced
(e.g. plastic with an aluminium foil top (Kwak et al.
1996).
The distinctive taste of kefir results from the presence
of several flavour compounds which are produced during
fermentation (Beshkova et al. 2003). Kefir produced from
pure cultures did not receive high sensory evaluation
scores in Canada unless it was sweetened (Duitschaever
et al. 1987, 1991); Duitschaever et al. (1987) also showed
that only about 40% of people tasting natural kefir for the
first time gave it a positive taste rating. Addition of peach Figure 1. Kefir grains. Reproduced with permission from
flavour, or modification of the fermentation process (e.g. Handbook of Fermented Functional Foods, Farnworth,
E.R. editor. Copyright CRC Press.
addition of lactococci, lactobacilli or yeasts) increased the
Kefir – a complex probiotic E.R. Farnworth
4
Table 2. Microorganisms* in kefir grains, mother
culture and kefir drink
Lactococci Lactobacilli Yeasts
Kefir grains 7.37 8.94 8.30
Mother culture 8.43 7.65 5.58
(wash of grains)
Kefir drink 8.54 7.45 5.24
*log CFU/g
1967; Koroleva et al. 1978). Analysis has shown that the
microbial profiles of the grains themselves, a percolate
taken from the grains (mother culture), and the final pro-
duct are not the same (see Table 2). This, in part, explains
why production of kefir must start with kefir grains, since
Figure 2. Electron micrograph of a kefir grain.
the final drink does not have the number or complexity of
microorganisms as the grains, preventing the drink from
cated in milk ‘at home with daily changes of milk’ and
being used as a starter culture for a new batch of kefir.
stored for three months either at room temperature or at
Kandler and Kunath (1983) reported similar results when
48C had microbiological profiles that were different to
they compared the microflora of kefir, inoculated milk
those of fresh grains (Pintado et al. 1996). In addition,
before incubation, and a mixture of kefir grains.
washing grains in water also reduced viability. It has been
recommended that in a commercial operation using grains
to produce kefir, grains should be kept viable through
6. Microbiology of kefir grains
daily transfers and should only be replaced if their ability
to ferment milk becomes impaired. (Koroleva 1982). Low
6.1 Bacteria
temperature storage appears to be the best way to maintain
kefir grains for long periods. Garrote et al. (1997) showed The microbial population found in kefir grains has been
that storage of kefir grains at À80 or À208C for 120 days used as an example of a symbiotic community (Margulis
did not change their fermentation properties compared to 1995); this symbiotic nature has made identification and
grains that had not been stored; however, grains stored at study of the constituent microorganisms within kefir grains
À48C did not produce acceptable kefir after thawing. Kefir difficult. Koroleva (1991) stated that kefir bacteria and
grains replicated in soy milk have been reported to be yeasts, when separated as pure cultures, either do not grow
smaller in size compared to grains replicated in cows’ in milk or have a decreased biochemical activity, which
milk (Liu et al. 2002). There have been no reports of suc- further complicates the study of the microbial population
cessful production of kefir grains from pure cultures. of kefir grains. Several media have been proposed for the
While early studies of kefir grains employed light isolation and identification of bacteria in kefir grains
microscopy, later investigations used electron microscopy (Kojima et al. 1993). Linossier and Dousset (1994)
to describe the complex microbial community of which showed that Lactobacillus kefir grew better when the yeast
they were comprised (Ottogalli et al. 1973; Bottazzi and Candida kefir was added to the milk. Garrote et al. (2004)
Bianchi 1980; Molska et al. 1980; Marshall et al. 1984; reported a similar observation when they attempted to
Duitschaever et al. 1988b; Toba et al. 1990; Neve 1992; grow L. kefir in milk. In general, lactic acid bacteria are
more numerous (108–109) than yeasts (105–106) and acetic
Bottazzi et al. 1994; Rea et al. 1996). Figure 2 shows an
acid bacteria (105–106) in kefir grains, although fermenta-
electron micrograph of kefir grains obtained from the
Moscow Dairy Institute. Ottogalli et al. (1973) showed tion conditions can affect this pattern (Koroleva 1991;
that the chemical and microbiological compositions of Garrote et al. 2001) Table 3 shows a list of the various
kefir grains from four different sources were different, bacteria that have been reported in kefir and kefir grains
making comparisons between results published by differ- from around the world.
ent laboratories difficult. Garrote et al. (2004) carried out several in vitro tests to
The microbial population that makes up kefir grains try to explain how the bacteria in kefir grains function.
appears to be relatively constant over time, although sea- They showed that two of the heterofermentative lactoba-
sonal variations in the grain flora have been noted which cilli, L. kefir and L. parakefir, possessed S-layer proteins
`
can affect the final product consistency (La Riviere et al. that can be used to explain in part their auto-aggregation
Kefir – a complex probiotic E.R. Farnworth 5
the yeasts in kefir grains provide an environment for the
Table 3. Bacteria found in kefir grains and kefir
growth of kefir bacteria, producing metabolites that contri-
Lactobacilli bute to the flavour and mouthfeel of kefir (Clementi et al.
kefir a,c,j,n,o,p,r Lactobacillus delbrueckii a,h,p
Lactobacillus
1989; Kwak et al. 1996; Simova et al. 2002). Table 4 lists
kefiranofaciens l,n,p Lactobacillus rhamnosus a,r
Lactobacillus
the various yeasts that have been reported in kefir grains.
kefirgranum n Lactobacillus casei h
Lactobacillus
To prevent excessive CO2 production (particularly after
parakefir n,o Lactobacilli paracasei p
Lactobacillus fermentation), Kwak et al. (1996) suggested a two stage
brevis g,h,p,r Lactobacillus fructivorans k
Lactobacillus fermentation process starting with a non-lactose ferment-
plantarum o,p Lactobacillus hilgardii k
Lactobacillus ing yeast such as Saccharomyces cerevisiae.
helveticus a,b,h Lactobacillus fermentum r
Lactobacillus The properties of yeasts found in kefir grains vary. For
acidophilus g,p,r Lactobacillus viridescens r example, some of the yeasts found in kefir grains are cap-
Lactobacillus
able of fermenting lactose, while some are not. Also, it
Lactococci
has been observed that some types of yeasts are located at
Lactococcus lactis subsp. lactis a,c,e,f,g,h,k,o,r
the surface of the grain, while others inhabit the interior.
Lactococcus lactis subsp. cremoris a,e,f
It may be that yeasts located at different locations in the
Streptococci kefir grains play different roles in the fermentation pro-
Streptococcus thermophilus e,h cess. (Iwasawa et al. 1982; Wyder et al. 1997). Iwasawa
et al. (1982) showed that the electrophoretic pattern of the
Enterococci
yeast Torulopsis holmii isolated from Danish kefir grains
**
Enterococcus durans d ,e
demonstrated patterns indicating the presence of ten differ-
(reported as Streptobacterium durans in ref. d; reported as
Streptococcus durans in ref. e) ent enzymes. Wyder et al. (1997) used restriction analysis
of the two ITS regions to show that yeasts from five kefir
Leuconostocs
grain samples of different origins had unique patterns,
Leuconostoc sp. r
indicating the presence of different yeast species in kefir
*
Leuconostoc mesenteroides a,b,g ,o
grains from different origins. Like kefir bacteria, the pro-
(reported as Leuconostoc kefir in ref. g)
file of yeasts is different in kefir grains when compared to
Acetic acid bacteria
the final kefir product (Wyder et al. 1997). Abraham and
Acetobacter sp. o De Antoni (1999) showed that the yeast population in
*
Acetobacter pasteurianus g kefir produced from cows’ milk using grains was two logs
(reported as Acetobacter rancens in ref. g)
higher than when the same grains were added to soy milk.
Acetobacter aceti a,d
Other bacteria
7. Other uses of kefir grains
Bacillus sp. r Micrococcus sp. r
Bacillus subtilis g Escherichia coli r The ability of kefir grains to grow in milk whey prompted
Rimada and Abraham (2001) to study whether kefir grains
a b c d
Koreleva 1991; Lin et al. 1999; Pintado et al. 1996; Rosi 1978; ref.
could be added to whey produced as a by-product of the
e f g
¨
Yuksekdag et al. 2004; Dousset and Caillet 1993; Ottogalli et al. 1973;
dairy industry in Argentina, thereby producing a value-
h j k
Simova et al. 2002; Kandler and Kunath 1983; Yoshida and Toyoshima
l n o
1994; Fujisawa et al. 1988; Takizawa et al. 1994; Garrote et al. 2001; added product called kefiran. Kefiran was produced at a
p r
Santos et al. 2003; Angulo et al. 1993.
rate of 103 mg/l following fermentation at 438C for 120 h,
with an inoculation rate of 100 g grains per litre of milk.
Athanasiadis et al. (1999) showed that kefir yeast cells
and haemagglutination properties. In addition, these
that had been immobilized on de-lignified cellulose were
two bacteria were also shown to adhere to Caco-2 cells,
capable of producing commercially important quantities of
raising the possibility that these bacteria would be good
ethanol from glucose over a wide variety of temperatures
probiotics.
(5–308C). Production of volatiles (e.g. ethanal, ethyl acet-
ate, propanol-1, isobutyl alcohol and amyl alcohols) was
found to depend on fermentation temperature. Ethyl acet-
6.2 Yeasts
ate content did not change as fermentation temperature
It has been recognized that yeasts play an important role decreased, although contents of total volatiles during fer-
in the preparation of fermented dairy products, where they mentations at 58C were 38% of those carried out at 308C.
can provide essential growth nutrients such as amino acids Using this system, it was shown that glucose produced the
and vitamins, alter the pH, secrete ethanol and produce fastest fermentation compared to fructose or sucrose,
CO2 (Viljoen 2001). The yeasts in kefir have been less although glucose-based fermentations also yielded lower
well studied than kefir bacteria, although it is obvious that concentrations of amyl alcohols, ethyl acetate and ethanol
Kefir – a complex probiotic E.R. Farnworth
6
Table 4. Yeasts found in kefir grains and kefir Table 5. Definitions of functional foods and probiotics
* *
Kluyveromyces marxianus a,b,f ,g,h,i,j,k,m ,n Candida friedrichii n Functional foods
(reported as Saccharomyces lactis in A functional food is one that is consumed as part of a usual diet,
ref. f; reported as Kluyveromyces lactis and is demonstrated to have physiological benefits and/or reduce
in ref. m) the risk of chronic disease beyond basic nutritional functions.
Saccharomyces sp. k Candida (Health Canada 2004)
pseudotropicalis f
Probiotics
*
Saccharomyces cerevisiae a,d,e,f ,g,j,m,n Candida tenuis f
Live microorganisms that, when administered in adequate
(reported as Saccharomyces carlbergensis
amounts, confer a health benefit on the host. (FAO/WHO 2002).
in ref. f)
Report of a Joint FAO/WHO Working Group, ‘Guidelines for
Saccharomyces unisporus c,h,j,m Candida the Evaluation of Probiotics in Food’, London, Ontario, Canada,
inconspicua g 2002.
*
Saccharomyces exiguus l Candida maris g
(reported as Torolopsis holmii in ref. l)
Saccharomyces turicensis h Candida lambica j (1982b) who reported decreases in biotin, vitamin B12 and
Saccharomyces delbrueckii d Candida pyridoxine, and significant increases in folic acid, as com-
tannotelerans e pared to non-fermented milk.
Saccharomyces dairensis n Candida valida 6 e
Torulaspora delbrueckii a,h,m Candida kefyr a,j,n
9. Bioactive ingredients in kefir
Brettanomyces anomalus h Candida holmii j,m
Issatchenkia occidentalis j Pichia The area of functional foods (see Table 5 for definition)
fermentans b,m,n has attracted a great deal of interest since it is now recog-
nized that many foods contain bioactive ingredients which
a b c d e
Koreleva 1991; Lin et al. 1999; Pintado et al. 1996; Rosi 1978; Dous-
g h
offer health benefits or disease resistance. A subset of
set and Caillet 1993; ref. fOttogalli et al. 1973; Simova et al. 2002; Wyder
i j
and Puhan 1997, 1999; Yoshida and Toyoshima 1994; Engel et al. 1986; functional foods is probiotic foods, from which there are
k m n
Garrote et al. 2001; ref. lIwasawa et al. 1982; Angulo et al. 1993; Rohm
several possible sources of bioactive ingredients. The
et al. 1992
microorganisms themselves (dead or alive), metabolites of
the microorganisms formed during fermentation (including
(Athanasiadis et al. 2001). The de-lignified cellulose mate-
antibiotics or bactericides), or breakdown products of the
rial supporting kefir yeast cells were able to ferment a
food matrix, such as peptides, may be responsible for
mixture of whey and raisins to produce a fermented pro-
these beneficial effects (Ouwehand and Salminen 1998;
duct with an alcohol content of 4.4% v/v.
Farnworth 2002; see Figure 3). Kefir has a long tradition
of offering health benefits, especially in eastern Europe
8. Composition of kefir ´
(Halle et al. 1994). There are several compounds in kefir
that may have bioactive properties.
The composition of kefir depends greatly on the type of
milk that was fermented (Kneifel and Mayer 1991). How-
ever, during the fermentation, changes in composition of
9.1 Exopolysaccharides
nutrients and other ingredients have also been shown to
occur. (Bottazzi et al. 1994). L(þ) lactic acid is the Exopolysaccharides of differing structures and composi-
tions are produced by a variety of lactic acid bacteria
organic acid in highest concentrations after fermentation
including Lactobacillus, Streptococcus, Lactococcus and
and is derived from approximately 25% of the original
Leuconostoc (De Vuyst and Degeest 1999; Ruas-Madiedo
lactose in the starter milk (Alm 1982d; Dousset and Cail-
et al. 2002.). These cell-surface carbohydrates confer pro-
let 1993). The amino acids valine, leucine, lysine and ser-
tective and adaptive properties on their bacterial produ-
ine are formed during fermentation, while the quantities of
cers; since they are often loosely bound to the cell mem-
alanine and aspartic acid increase when compared to raw
milk (Alm 1982e). Bottazzi et al. (1994) reported the brane, they are, therefore, easily lost to their environment
(Jolly et al. 2002). In food products, exopolysaccharides
occurrence of acetic acid in their kefir, although others
¨ often contribute to organoleptic and stability characteris-
reported that no acetic acid was present (Guzel-Seydim
et al. 2000a, 2000b). tics. A unique polysaccharide called kefiran has been
found in kefir grains; grains may also contain other exopo-
Kneifel and Mayer (1991) found that appreciable
lysaccharides.
amounts of pyridoxine, vitamin B12, folic acid and biotin
Kefiran contains D-glucose and D-galactose only in a
were synthesized during kefir production, depending on
ratio of 1:1. Hydrolysis reactions followed by NMR ana-
the source of kefir grains used, while thiamine and ribofla-
lyses have been used to determine the chemical structure
vin levels were reduced. These results contrast with Alm
Kefir – a complex probiotic E.R. Farnworth 7
exopolysaccharides in different media (Grobben et al.
Probiotic
1995; Van Geel-Schutten et al. 1999). Furthermore, Santos
(Kefir) et al. (2003) recently reported that they have also isolated
an exopolysaccharide closely related to kefiran.
Kefiran dissolves slowly in cold water and quickly in
hot water, and forms a viscous solution at 2% concentra-
Fermentation Bacteria, Yeasts Metabolites
´
tion (La Riviere et al. 1967). Carboxymethyl kefiran has a
Products
viscosity that is 14 times that of kefiran, although this is
still much lower than those of other thickening agents
used in the food industry, thus limiting any practical uses
of kefiran or carboxymethyl kefiran (Mukai et al. 1990).
Intestinal Microbial Digestion, Metabolism,
Kefiran can form weak gels when added to k-carrageenan
Population Immune Status,
Disease Resistance (1% 1:4 kefiran/k-carrageenan), which have gelation tem-
peratures and melting temperatures similar to those of
Figure 3. Probiotic effects on metabolism and health.
guar/k-carrageenan gels (Pintado et al. 1996).
Since its initial isolation, it has been reported that
kefiran may be produced by a variety of bacteria isolated
of kefiran (see Figure 4). The proposed structure is a
from kefir grains which have been obtained from several
branched hexa- or heptasaccharide repeating unit that is
´
sources (La Riviere and Kooiman 1967; Toba et al. 1987;
itself composed of a regular pentasaccharide unit to which
Mukai et al. 1990; Hosono et al. 1990; Yokoi et al. 1991;
one or two sugar residues are randomly linked (Kooiman
Pintado et al. 1996; Mitsue et al. 1999; Micheli et al.
1968; Micheli et al. 1999). Subsequent methylation/hydro-
1999; Santos et al. 2003). Whether in fact the bacteria
lysis studies have shown that the structure of kefiran may
reported are the same has not been studied, nor has any
be more complex than first thought (Mukai et al. 1988;
definitive identification been published to fully character-
Mukai et al. 1990). Methylation and NMR analyses have
ize those bacteria reported as kefiran producers.
also been used to verify the production of kefiran by new
Bacteria which produce exopolysaccharides are often
bacterial strains (Yokoi et al. 1991). A closer examination
found in milk or milk products, although studies have
of chemical data published by Mukai et al. (1990) raises
shown that maximum production of exopolysaccharide
the question if, in fact, two exopolysaccharides are being
may occur in chemically defined media (containing a
produced that have very similar chemical structure and
´ carbohydrate source, mineral salts, amino acids/peptides,
properties. La Riviere et al. (1967) reported that their
vitamins and nucleic acids) at a constant pH (Mozzi
kefiran had a 1:1 glucose to galactose ratio and an optical
rotation of þ68.08, while Mukai et al. (1990) isolated a et al. 1996; Dupont et al. 2000). The potential health
properties of kefiran have prompted several groups to
kefiran with a glucose to galactose ratio of 0.9:1.1 and an
optical rotation of þ548. Examples can be found in the lit- develop media and growing conditions that optimize
kefiran production (Toba et al. 1987; Yokoi et al. 1990;
erature where the same bacterial strain produced different
→ 6)-β-D-Gp-{1→2(6)}-β-D-Galp-(1→4)-α-D-Galp-(1→3)-β -D-Galp-(1→4)-β-D-Gp-(1
6(2)
↑
21
1
β-D-Gp
Figure 4. Proposed chemical structure of kefiran. Reprinted from Carbohydrate Research 7, Kooiman, P. The chemical
structure of kefiran, the water-soluble polysaccharide of the kefir grain, pp 200–211. Copyright 1968 with permission
from Elsevier.
8
Delta O.D. /cfu/ml(x10-12)
8
IM
Lc. lactis
7
6
5
4
3
2
1
0
10
1
IM
10
5
IM
00
2
IM
00
5
IM
00
8
IM
01
1
IM
02
2
IM
02
3
IM
01
4
IM
01
5
IM
08
2
Kefir – a complex probiotic E.R. Farnworth
Lb. kefirgranum
Lb. helveticus
Lb. kefir
Ln. mesenteroides
Lc. cremoris (Prt-)
Kefir Strains Reference Strains
Figure 5. Proteinase activity of bacteria from kefir and kefir grains.
9.2 Bioactive peptides
Yokoi and Watanabe 1992; Micheli et al. 1999; Mitsue
et al. 1999). Media based on lactic acid whey have been
Many organisms possess enzymes (e.g. proteinases and
found to be optimum for kefiran production. A batch
peptidases) that are able to hydrolyse the protein in a med-
procedure using a modified MRS media (MRSL) was
ium, thereby supporting growth of the organism by liberat-
reported by Micheli et al. 1999 to produce consistent
ing peptides and amino acids (Thomas and Pritchard
yields of 2 g/l of kefiran. The best kefiran yields, how-
1987; Matar et al. 1996). The action of proteinase and
ever, have been reported by Mitsue et al. (1999) when
peptidase enzymes on milk proteins can theoretically
they combined the kefiran producing bacterium, Lactoba-
result in a very large number of possible peptides. An ana-
cillus kefiranofaciens, with the yeast Torulaspora del-
lysis of the proteinase activity of kefir grain bacterial iso-
brueckii. When these two organisms were grown in a 50
lates has shown that several isolates have high proteinase
l fermentor in a fed-batch protocol, a yield of 3740 mg/l
activities (see Figure 5), which increases the possibility
was obtained over a 7 day period.
that bioactive peptides may be present in kefir. In their
No measurements have been reported with regard to
˘
¨
study of lactic acid bacteria in Turkish kefir, Yuksekdag
kefiran concentration in the final kefir product. However,
et al. (2004b) showed that 13 out of 21 lactococci strains
a comparison of the carbohydrate content of milk
had measurable proteolytic activity.
(USDA 2004) and that of kefir shows a more than dou-
Initial studies on the peptide content of kefir drink have
bling of the carbohydrate content; how much of this is
shown that kefir contains a large number of peptides and
kefiran is not known. Abraham and De Antoni (1999)
that the majority of kefir peptides have molecular weights
did show that the polysaccharide content of kefir from
of 5000 kDa (Farnworth 2005, unpublished results).
cows’ milk was almost twice that of kefir produced
from soy milk.
Kefir grains grown in soy milk produce an exopolysac-
10. Health benefits of kefir
charide that Liu et al. (2002) have shown to be primarily
composed of D-glucose and D-galactose (ratio 1.00: 0.43), Kefir has had a long history of being beneficial to health
with a molecular weight of approximately 1.7 Â 106 Da. in Eastern European countries, where it is associated with
Kefir – a complex probiotic E.R. Farnworth 9
general wellbeing. It is easily digested (Alm 1982c) and is the polysaccharide stimulated PP cells, causing them to
often the first weaning food received by babies. Many of secrete water-soluble factors that, in turn, enhanced the
the studies regarding health benefits of kefir have been mitogenic response of thymocytes and splenocytes in nor-
published in Russian and Eastern European journals and mal mice.
therefore are not easily accessible to Western science
(Batinkov 1971; Ormisson and Soo 1976; Evenshtein
10.2 Inhibition of tumour growth
1978; Safonova et al. 1979; Ivanova et al. 1981; Sukhov
et al. 1986; Besednova et al. 1997; Oleinichenko et al. Shiomi et al. (1982) were the first to report the antitumour
effects of a water-soluble polysaccharide (approximate
1999). However, the health benefits of kefir were demon-
molecular weight 1 000 000 Da) isolated from kefir grains.
strated in Canada as early as 1932 (Rosell 1932).
Whether given orally or intraperitoneally, the polysacchar-
ide was able to inhibit the growth of Ehrlich carcinoma or
10.1 Stimulation of the immune system
Sarcoma 180 compared to control mice receiving no kefir-
derived polysaccharide (Shiomi et al. 1982; Murofushi
It has been proposed that stimulation of the immune sys-
et al. 1983). The mechanism of action was not clear, since
tem may be one mechanism whereby probiotic bacteria
in vitro incubation of the two cancer cell lines with the
may exert many of their beneficial effects (De Simone
et al. 1991; Gill 1998); this may be a direct effect of the polysaccharide showed low cytotoxicity during 42 hours of
bacteria themselves (Cross 2002). However, peptides incubation. This group then went on to show that this
formed during the fermentation process or during diges- water-soluble polysaccharide was able to reach the spleen
tion have also been shown to be bioactive, and demon- and thymus of mice and, based on the response to thymus-
strate a variety of physiological activities, including stimu- dependent and thymus-independent antigens, concluded
lation of the immune system in animal models (LeBlanc that oral immune enhancement was mediated through T-
et al. 2002; Matar et al. 2003). cell, but not B-cell activity. (Murofushi et al. 1986). More
Thoreux and Schmucker (2001) fed kefir produced from recently, a water soluble polysaccharide fraction from kefir
grains to young (6 months) and old (26 months) rats and grains was shown to inhibit pulmonary metastasis of Lewis
found an enhanced mucosal immune response in the lung carcinoma, whether the kefir-derived polysaccharide
young animals, as shown by a higher anti-cholera toxin was given orally before or after tumour transplantation.
Murofushi et al. (1983) also reported the antitumour effec-
(CT) IgA response compared to controls. Both young and
old rats had significantly increased total non-specific IgG tiveness of kefir grain polysaccharides regardless of the
blood levels, and a decreased systemic IgG response to time of administration, although they cautioned that larger
CT. Taken together, Thoreux and Schmucker concluded doses may only be more effective if administered after
that kefir, like other probiotics, was exerting an adjuvant establishment of the tumours. A water-insoluble fraction
effect on the mucosal immune system, perhaps produced containing kefir grain microorganisms, rather than the
by bacterial cell wall components. water-soluble polysaccharide fraction, significantly inhib-
Stimulation of the immune system may also occur due ited metastasis of highly colonized B16 melanoma. (Furu-
kawa et al. 1993; Furukawa et al. 2000). It was suggested
to the action of exopolysaccharides found in kefir grains.
Murofushi et al. (1983, 1986) used the method of La Riv- that the water-soluble polysaccharide suppressed tumour
´
iere et al. (1967) for the extraction of kefiran from kefir growth by means of the lymphokine activated macrophage
grains to produce a water-soluble polysaccharide fraction (Mf) via the gut-associated lymphoid tissue, while the
that they fed to mice. The reduction in tumour growth that water-insoluble microorganism fraction acted through an
they observed was linked to a cell-mediated response, and increase of NK cell activity.
it appeared that the total dose of the polysaccharide deter- Feeding kefir itself (2 g/kg body weight by intubation)
mined its effectiveness. Furukawa et al. (1992) have also was more effective in inhibiting tumour (Lewis lung carci-
shown that a water-soluble fraction of kefir grains may act noma) growth than yoghurt, when given for 9 days after
tumour inoculation (Furukawa et al. 1990). It was also
as a modulator of the immune response.
The effect of kefir exopolysaccharides on the immune shown that mice receiving kefir had an improved delayed-
system may be dependent on whether the host is healthy type hypersensitivity response compared to tumour-bearing
or has developed any tumours. Furukawa et al. (1996) mice receiving no kefir, although the mean survival time
was not affected (Furukawa et al. 1991). Kubo et al.
incubated kefir grain polysaccharides with Peyer’s Patch
(PP) cells from tumour-bearing mice and found that the (1992) also reported that feeding kefir (100–500 mg/kg
supernatant of this mixture enhanced proliferation of sple- body weight) inhibited the proliferation of Ehrlich ascites
nocytes from normal mice and increased the mitogenic carcinoma. In addition, kefir, from which the grains had
activities of lipopolysaccharides (LPS) and phytohaemag- been removed by filtration, were shown to kill or arrest
glutinin-P (PHA-P) in splenocytes. They concluded that the growth of fusiform cell sarcomas induced by 7,12-
Kefir – a complex probiotic E.R. Farnworth
10
10.3 Kefir and lactose intolerance
dimethylbenzanthracene in mice when the kefir was
injected intraperitoneally (Cevikbas et al. 1994). Examina-
A proportion of the global population is unable to digest
tion of tissue in kefir-treated mice showed a small amount
lactose (the major sugar found in milk), because of insuffi-
of mitosis, some stromal connections and, in some cases,
cient intestinal b-galactosidase (or lactase) activity (Alm
disappearance of tumour necrosis.
1982a). Research has shown, however, that lactose maldi-
Hosono et al. (1990) showed that isolates of Streptococ-
gestors are able to tolerate yoghurt, providing the number
cus, Lactobacillus and Leuconostoc in Mongolian kefir all
of live bacteria present in the yoghurt consumed is high
showed strong in vitro binding to amino acid pyrolysates
enough (Pelletier et al. 2001). It is believed that the bac-
which are believed to be mutagens and are commonly
teria in the yoghurt matrix are protected by the buffering
found in food. Similarly, Miyamoto et al. (1991) reported
effect of the yoghurt. Bacterial cells remain viable, and
that three slime-producing strains of Streptococcus lactis
the bacterial cell walls remain intact, and thus the b-galac-
subsp. cremoris found in German kefir had strong desmu-
tosidase enzyme contained in the yoghurt-producing bac-
tagenic properties, which they attributed to the ability of
teria (L. acidophilus) is protected during transit through
such strains to bind to a known mutagen. Using an Ames
the stomach until it arrives at the upper gastrointestinal
test, Yoon et al. (1999) showed that Lactobacillus spp.
tract (Montes et al. 1995; De Vrese et al. 2001). It has
isolated from kefir and yoghurt had antimutagenic proper-
also been shown that fermented milk products have a
ties against the mutagen 2-nitrofluorene.
slower transit time than milk, which may further improve
Liu et al. (2002) studied the effects of soy milk and
lactose digestion (Vesa et al. 1996; Labayen et al. 2001).
cows’ milk fermented with kefir grains on the growth of
Some kefir grains have been shown to possess b-galac-
tumours in mice, using freeze-dried kefir (produced from
tosidase activity which remains active when consumed
either soy or cows’ milk) from which the grains had been
(De Vrese et al. 1992). A recent study has shown that a
removed following fermentation. Mice were injected with
commercial kefir produced using a starter culture contain-
0.2 Â 108 Sarcoma 180 cells one week prior to the start
ing six bacteria (but not L. acidophilus) and one yeast was
of the feeding portion of the experiment. Tumour growth
equally as effective as yoghurt in reducing breath hydro-
(volume) was estimated for up to 30 days, after which
gen in adult lactose maldigestors (Hertzler and Clancy
tumours were removed and weighed. Both soy milk kefir
2003). Severity of flatulence in this group was also
(À70.9%) and cows’ milk kefir (À64.8%) significantly
reduced when either yoghurt or kefir was consumed com-
inhibited tumour growth, compared to mice in the positive
pared to milk.
control group. Microscopic examination of the tumours
De Vrese et al. (1992) showed that when pigs were fed
indicated that apoptosis may have been responsible for
kefir containing fresh grains, their plasma galactose con-
reduced tumour growth. Similar effects of yoghurt on
centrations rose significantly higher than pigs given kefir
apoptosis have been reported (Rachid et al. 2002). Mice
containing heated grains. The diet containing kefir and
fed unfermented soy milk did not have reduced tumour
fresh grains had a b-galactosidase activity of 4.4 U/l, which
volumes at day 30, and Liu et al. (2002) concluded that
was identified as being responsible for the hydrolysis of
either the microorganisms themselves or any polysacchar-
lactose in the intestine, thus yielding galactose that can be
ides formed during fermentation by the kefir grains micro-
absorbed. Kefir itself contains no galactose (Alm 1982).
flora were responsible for the antitumour response. Genis-
tein itself has been shown to inhibit tumours (Murrill
et al. 1996; Constantinou et al. 1996), although in this
10.4 Antimicrobial properties of kefir
study genistein levels did not change during the fermenta-
There are data to show that many lactobacilli are capable
tion process. Mice consuming kefir samples also had sig-
nificantly increased levels of IgA in their small intestines of producing a wide range of antimicrobial compounds,
compared to control animals, and it was proposed that the including organic acids (lactic and acetic acids), carbon
dioxide, hydrogen peroxide, ethanol, diacetyl and peptides
PP tissue was increasing IgA secretion into the intestine in
(bacteriocins) that may be beneficial not only in the reduc-
response to food antigens.
¨
Guven et al. (2003) proposed an alternative suggestion tion of foodborne pathogens and spoilage bacteria during
as to how kefir may protect tissues. They showed that food production and storage, but also in the treatment and
prevention of gastrointestinal disorders and vaginal infec-
mice exposed to carbon tetrachloride (a hepatotoxin to
tions (Tahara and Kanatani 1997; Zamfir et al. 1999;
induce oxidative damage) and given kefir by gavage had
´
decreased levels of liver and kidney malondialdehyde, Bonade et al. 2001; Messens and De Vuyst 2002; Jamuna
indicating that kefir was acting as an antioxidant. Further- and Jeevaratnam 2004).
Garrote et al. (2000) tested the inhibitory activity of a
more, their data showed that kefir was more effective than
supernatant of cows’ milk fermented with kefir grains,
vitamin E (which is well known to have antioxidative
properties) in protecting against oxidative damage. against Gram-negative and Gram-positive bacteria. Gram-
Kefir – a complex probiotic E.R. Farnworth 11
10.5 Behaviour of kefir bacteria in the
positive microorganisms were inhibited to a greater extent
than Gram-negative microorganisms; moreover, both lactic gastrointestinal tract
and acetic acids were found in the supernatants. Garrote
One of the criteria for probiotic bacteria is that they
et al. (2000) showed that milk supplemented with lactic
should be able to withstand the harsh conditions of the
acid or lactic acid plus acetic acid at the concentrations
gastrointestinal tract, including extreme pH conditions pre-
found in the kefir supernatant also had inhibitory activity
sent in the stomach and the action of bile salts and diges-
against E. coli 3. They concluded that organic acids pro-
tive enzymes (Lee and Salminen 1995). It is also believed
duced during kefir fermentation could have important bac-
that one way in which probiotic bacteria could protect
teriostatic properties even in the early stages of milk fer-
against pathogenic bacteria would be to compete with or
mentation. Cevikbas et al. (1994) found similar results
displace pathogenic bacteria by adhering to intestinal
against Gram-positive coccus, staphylococcus, and Gram-
epithelial cells. (Kirjavainen et al. 1998; Fujiwara et al.
positive bacillus, and noted that kefir grains were more
2001; Gibson and Rastall 2003).
effective with regard to their antibacterial properties than
No results from human feeding trials have been pub-
the final kefir product.
lished with regard to the ability of the microorganisms
Kefir grains themselves have inhibitory power against
found in kefir to traverse the upper GI tract in large num-
bacteria that can be preserved during lyophilization, parti-
bers and arrive at the large intestine. Kefir, because it is
cularly when glycerol is added as a cryopreservative
milk based, is able to buffer the pH of the stomach when
(Brialy et al. 1995). Fresh kefir grains were found to inhi-
ingested and thereby provide time for many of the bacteria
bit the growth of the bacteria Streptococcus aureus, Kleb-
to pass through to the upper small intestine (Farnworth
siella pneumoniae and Escherichia coli, but not the yeasts
et al. 2003). Santos et al. (2003) isolated 58 strains of
Candida albicans and Saccharomyces cerevisiae. Leuco-
Lactobacillus spp. and isolates of L. paracasei, L. plan-
nostoc mesenteroides and Lactobacillus plantarum, iso-
tarum, L. delbrueckii, L. acidophilus and L. kefiranofa-
lated from kefir grains, have both been shown to produce
ciens from different sources of kefir grains and exposed
antimicrobial compounds that are present in kefir. Both
them to an MRS medium at pH 2.5 and MRS containing
inhibit Gram-positive and Gram-negative bacteria, have a
0.3% Oxgall (bile salts). They found that all strains sur-
molecular weight of approximately 1000 kDa and are heat
vived 4 h incubation at pH 2.5, but did not grow. Eighty-
stable, although their antimicrobial properties are reduced
five percent of isolates showed high resistance to Oxgall,
after exposure to proteolytic enzymes (Serot et al. 1990).
but had delayed growth.
Santos et al. (2003) showed that lactobacilli isolated from
The caco-2 cell assay has been used to show that many
kefir grains had antimicrobial activities against E. coli (43/
of the lactobacilli isolated from kefir grains are able to
58 strains), Listeria monocytogenes (28/58 strains), Salmo-
bind to enterocyte-like cells (Santos et al. 2003), although
nella typhimurium (10/58 strains), S. enteritidis (22/58
the authors also cautioned that results using this model
strains), S. flexneri (36/58 strains) and Yersinia enterocoli-
might not necessarily apply in vivo.
tica (47/58 strains). Bacteriocins were thought to be
Human studies of the effects of diet on intestinal micro-
responsible, although they were not identified.
flora are limited to the analysis of faecal samples,
In a study in which foodborne bacterial pathogens (E.
although no detailed human study has been published in
coli O157:H7, L. monocytogenes 4b, Y. enterocolitica 03)
which kefir has been used. Marquina et al. (2002) used
were added at the beginning of yoghurt or kefir fermenta-
mice to study the effect of consuming kefir (source not
tion, both kefir and yoghurt failed to inhibit pathogenic
defined) in a feeding study that lasted 7 months. They
bacterial growth. For kefir, this was explained as being
were able to show that the numbers of lactic acid bacteria
due to the slow acid development during fermentation.
in the mouse small and large intestines increased signifi-
Interestingly, fermentations of kefir and yoghurt combina-
cantly. Streptococci increased by 1 log, while sulfite-redu-
tions proved to be more effective at pathogen suppression
cing clostridia decreased by 2 logs.
than single fermentation (Gulmez and Guven 2003)
Hydrogen peroxide is another metabolite produced by
˘
¨
some bacteria as an antimicrobial compound. Yuksekdag
et al. (2004a) showed that all 21 isolates of lactic acid
10.6 Kefir and cholesterol metabolism
bacteria from Turkish kefir produced hydrogen peroxide
Positive effects of yoghurt consumption on cholesterol
(0.04–0.19 ug/ml). In a later paper, they reported that 11
out of 21 strains of kefir lactococci produced hydrogen metabolism have been reported (Kiessling et al. 2002;
˘
¨
peroxide (Yuksekdag et al. 2004b). All lactococci strains Xiao et al. 2003), although a review of the literature
were effective in inhibiting growth of Streptococcus aur- reveals that the results are at best moderate, and are often
inconsistent (Taylor and Williams 1998; St-Onge et al.
eus, but were less effective against E. coli NRLL B-704
and Pseudomonas aeruginosa. 2000; Pereira and Gibson 2002).
Kefir – a complex probiotic E.R. Farnworth
12
Several hypotheses have been proposed regarding the found in kefir. Furthermore, there is evidence to show that
possible mechanism of action employed by bacteria to kefir consumption not only affects digestion, but also
reduce cholesterol levels (St. Onge et al. 2002). Vujicic influences metabolism and immune function in humans.
et al. (1992) showed that kefir grains from Yugoslavia,
Hungary and the Caucase region were able to assimilate 12. References
cholesterol in milk either incubated at 208C for 24 h
Abraham, A.G. and De Antoni, G.L. 1999. Characterization of
(reductions of up to 62%) or incubated and stored at 108C kefir grains grown in cows’ milk and in soya milk. Journal of
for 48 h (reductions of up to 84%). These authors claimed Dairy Research 66: 327-333.
that their results indicated that kefir grains had a choles- Alm, L. 1982a. Effect of fermentation on lactose, glucose, and
galactose content in milk and suitability of fermented milk
terol-degrading enzyme system. Similar results were
products for lactose intolerant individuals. Journal of Dairy
reported for 27 lactic acid bacterial strains. However, it
Science 65: 346-352.
was pointed out that isolates from dairy products had Alm, L. 1982b. Effect of fermentation on B-vitamin content of
lower cholesterol-assimilating capacity than strains iso- milk in Sweden. Journal of Dairy Science 65: 353-359.
lated from infant faeces (Xanthopoulos et al. 1998). Alm, L. 1982c. Effects of fermentation on curd size and digest-
ibility of milk proteins in vitro of Swedish fermented milk
In a clinical trial in which 13 subjects were fed 500 ml/
products. Journal of Dairy Science 65: 509-514.
day of kefir for 4 weeks in a placebo-controlled design, per-
Alm, L. 1982d. Effect of fermentation on L(þ) and D(À) lactic
centage changes in serum triglycerides compared to base- acid in milk. Journal of Dairy Science 65: 515-520.
line levels were lower (although not significantly) than Alm, L. 1982e. Effect of fermentation on proteins of Swedish
when subjects consumed unfermented milk; the percentage fermented milk products. Journal of Dairy Science 65: 1696-
1704.
serum high-density lipoprotein (HDL) cholesterol change
Angulo, L., Lopez, E. and Lema, C. 1993. Microflora present in
compared to baseline increased (although not significantly)
kefir grains of the Galician region (North-West of Spain).
when subjects consumed kefir compared to milk (St. Onge Journal of Dairy Research 60: 263-267.
et al. 2002). Similarly, Kiessling et al. (2002) found that Arihara, K., Toba, T. and Adachi, S. 1990. Immunofluorescence
HDL levels increased after 6 months of feeding yoghurt microscopic studies on distribution of Lactobacillus kefiranofa-
ciens and Lactobacillus kefir in kefir grains. International
supplemented with Lactobacillus acidophilus and Bifido-
Journal of Food Microbiology 11: 127-134.
bacterium longum, thereby producing an improved low-
Athanasiadis, I., Boskou, D., Kanellaki, M. and Koutinas, A.A.
density lipoprotein (LDL)/HDL cholesterol ratio. 1999. Low-temperature alcoholic fermentation by delignified
cellulosic material supported cells for kefir yeast. Journal of
Agricultural and Food Chemistry 47: 4474-4477.
11. Conclusions Athanasiadis, I., Boskou, D., Kanellaki, M. and Koutinas, A.A.
2001. Effect of carbohydrate substrate on fermentation by kefir
Many probiotic products have been formulated that con-
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Yoshida, T. and Toyoshima, K. 1994. Lactic acid bacteria and
Kefir – a complex probiotic
Edward R. Farnworth
Food Research and Development Centre, Agriculture and Agri-food Canada, St. Hyacinthe, Quebec, Canada J2S 8E3.
Tel. 450-773-1105. Fax 450-8461. E-mail farnworthed@agr.gc.ca
Abstract
Kefir is a fermented milk drink produced by the actions of bacteria and yeasts contained in kefir grains, and
is reported to have a unique taste and unique properties. During fermentation, peptides and exopolysacchar-
ides are formed that have been shown to have bioactive properties. Moreover, in vitro and animal trials have
shown kefir and its constituents to have anticarcinogenic, antimutagenic, antiviral and antifungal properties.
Although kefir has been produced and consumed in Eastern Europe for a long period of time, few clinical
trials are found in the scientific literature to support the health claims attributed to kefir. The large number of
microorganisms in kefir, the variety of possible bioactive compounds that could be formed during fermenta-
tion, and the long list of reputed benefits of eating kefir make this fermented dairy product a complex
probiotic.
Keywords: kefir, probiotics, kefir grains, kefiran, human health, bioactive ingredients
known than yoghurt; however, an analysis of its composi-
1. Introduction
tion indicates that it may contain bioactive ingredients that
Archaeological evidence has indicated that the process of give it unique health benefits, which means that kefir may
fermentation in foods was discovered accidentally thou- be an important probiotic product (Farnworth 1999).
sands of years ago. However, over time, it soon became
apparent that many fermented foods had longer storage
2. Origins of kefir
lives and improved nutritional values compared to their
Kefir is a viscous, slightly carbonated dairy beverage that
unfermented equivalents, making this form of food proces-
contains small quantities of alcohol and, like yoghurt, is
sing a popular technique. It is not surprising, therefore, to
believed to have its origins in the Caucasian mountains of
find that many foods including vegetables, fruits, cereals,
the former USSR. It is also manufactured under a variety
meat and fish have all been converted into desirable food
of names including kephir, kiaphur, kefer, knapon, kepi
products by fermentation and are still being consumed
and kippi (Koroleva 1988a), with artisanal production of
throughout the world today (Farnworth 2004).
kefir occurring in countries as widespread as Argentina,
Certain bacteria, either alone or through the changes
Taiwan, Portugal, Turkey and France (Thompson et al.
they bring about during fermentation, have been shown to
1990; Angulo et al. 1993; Lin et al. 1999; Garrote et al.
have positive effects on health as well as resistance to dis-
2001; Santos et al. 2003; Gulmez and Guven 2003). It is
ease. Interest in such probiotic species has increased in
not clear whether all kefirs originate from a single original
recent years as more is learned about the microorganisms
starter culture, since microbial analyses of kefir samples
used in the fermentation process, and the possibility of
taken from different locations indicate microflora popula-
adding beneficial bacteria to food products. Furthermore,
tion differences.
consumers are increasingly looking to improve their health
The FAO/WHO (2001) have proposed a definition of
and increase their resistance to disease through dietary
kefir based on the microbial composition of both kefir
means.
grains (the starter culture used to produce kefir) and the
Fermented dairy products from milk from a variety of
final kefir product (see Table 1).
animals are perhaps the most common fermented foods
worldwide. Yoghurt, which is known by many different
names in different countries, is a fermented product which 3. Kefir manufacture
is familiar to consumers. Kefir, meanwhile, is less well
Although commercial kefir is traditionally manufactured
from cows’ milk, it has also been made from the milk of
Food Science and Technology Bulletin: Functional Foods 2 (1) 1–17
ewes, goats and buffalos. Moreover, kefir produced using
DOI: 10.1616/1476-2137.13938. Published 4 April 2005
ISSN 1476-2137 # IFIS Publishing 2005. All Rights Reserved soy milk has also been recently reported (Ismail et al.
Kefir – a complex probiotic E.R. Farnworth
2
lactic acid production and ethanol production, compared
Table 1. Codex Alimentarius description of kefir*
to kefir produced from soy milk alone (Liu and Lin 2000).
Definition
The grains used in this study were found to have a-galac-
Starter culture prepared from kefir grains, Lactobacillus kefiri, tosidase activity that helped explain how these kefir grains
and species of the genera Leuconostoc, Lactococcus and
were able to use the galactose-based carbohydrates which
Acetobacter growing in a strong specific relationship. Kefir
occur in soy milk.
grains constitute both lactose-fermenting yeasts (Kluyveromyces
Kefir grains are key to kefir production, and it has been
marxianus) and non-lactose-fermenting yeasts (Saccharomyces
unisporus, Saccharomyces cerevisiae and Saccharomyces found that the finished product has a different microbiolo-
exiguus). gical profile from the grains and therefore cannot be used
to inoculate a new batch of milk (Simova et al. 2002).
Composition
Grains have been shown to possess a dynamic and com-
Milk protein (% w/w) min. 2.8
plex flora which is not conducive to commercial produc-
<10
Milk fat (% m/m)
tion of a uniform, stable product; this has prompted
Titratable acidity, expressed as % of lactic acid min. 0.6
groups to try to produce kefir from a mixture of pure cul-
(% m/m)
tures (Petersson et al. 1985). Duitschaever et al. (1987,
Ethanol (% vol./w) not stated
1988a) combined a yoghurt culture with three other lactic
min. 107
Sum of specific microorganisms constituting the
acid bacteria and Saccharomyces cerevisiae (a non-lactose
starter culture (cfu/g, in total)
fermenting yeast) to produce a fermented milk with kefir
min. 104
Yeasts (cfu /g)
characteristics (which produced CO2 and contained etha-
*From Codex Standard for Fermented Milks CODEX STAN 243-2003
nol) under a variety of conditions. Rossi and Gobbetti
(1991) produced a multistarter culture using four bacteria
and two yeasts isolated from kefir grains in order to manu-
´
1983; Mann 1985; Zourari and Anifantakis 1988; Halle facture kefir under a continuous process. More recently,
et al. 1994; Kuo and Lin 1999). Traditionally, kefir is pro- Beshkova et al. (2002) produced a starter consisting of
duced by adding kefir grains (a mass of proteins, polysac- two bacteria (Lactobacillus helveticus and Lactococcus
charides, mesophilic, homofermentative and hetero- lactis subsp. lactis,) and one yeast (S. cerevisiae) isolated
fermentative lactic acid streptococci, thermophilic and from kefir grains and combined with two yoghurt strains
mesophilic lactobacilli, acetic acid bacteria, and yeast) to (Lactobacillus delbrueckii subsp. bulgaricus, and Strepto-
´
a quantity of milk (Koroleva 1982; Halle et al. 1994; coccus thermophilus). Yeast was added to the starter with
Tamime et al. 1999). The size of the initial kefir grain sucrose either at the beginning, or after lactic acid fermen-
inoculum affects the pH, viscosity and microbiological tation. The two resulting kefirs produced were found to
profile of the final product (Koroleva and Bavina 1970; have high numbers of viable cocci and lactobacilli and
Garrote et al. 1998). Koroleva (1991) reported that grain had chemical and organoleptic properties that were similar
to milk ratios of 1:30 to 1:50 were optimum. In some to traditional kefir. A commercial kefir is being produced
manufacturing procedures, a perculate of the grains from a in the United States using a mixture of defined microor-
coarse sieve is used as the mother culture to inoculate ganisms rather than kefir grains. This starter culture mix-
fresh milk. Fermentation of the milk by the inoculum pro- ture has been reported to contain Streptococcus lactis, L.
ceeds for approximately 24 hours, during which time plantarum, Streptococcus cremoris, L. casei, Streptococcus
homofermentative lactic acid streptococci grow rapidly, diacetylactis, Leuconostoc cremoris and Saccharomyces
initially causing a drop in pH. This low pH favours the florentinus (Hertzler and Clancy 2003).
growth of lactobacilli, but causes the streptococci numbers Starter cultures containing freeze-dried lactic acid bac-
to decline. The presence of yeasts in the mixture, together teria and yeasts from kefir grains are now available com-
with fermentation temperature (21–238C), encourages the mercially; some are supplemented with additional microor-
growth of aroma-producing heterofermentative strepto- ganisms to impart desirable characteristics in the finished
cocci. As fermentation proceeds, growth of lactic acid kefir product (Piotr Kolakowski, private communication).
bacteria is favoured over growth of yeasts and acetic acid It is evident that the final product, as produced from kefir
bacteria (Koroleva 1982). grains, will have a larger number and variety of microor-
Taiwanese researchers have shown that the lactic acid ganisms than kefir produced from a mixture of a small
bacteria from kefir grains grow more slowly in soy milk number of pure cultures.
compared to cows’ milk (Liu and Lin 2000). This may be Kefir is still most familiar to consumers in Eastern Eur-
due, in part, to the slower production of growth factors at ope, although commercial production now occurs in North
the beginning of fermentation when soy milk is the America. However, several patents can be found relating
substrate rather than cows’ milk. Addition of carbohydrate to commercial kefir production worldwide (Klupsch 1984;
(e.g. 1% glucose) to soy milk increases yeast numbers, Dmitrovskaya 1986; Tokumaru et al. 1987; Kabore 1992).
Kefir – a complex probiotic E.R. Farnworth 3
Production/consumption figures for kefir are not readily acceptability of kefir, compared to traditionally made kefir
(Duitschaever et al. 1991; Muir et al. 1999).
available since statistics for fermented dairy products are
not always broken down into separate items such as Acetaldehyde and acetoin have received particular
yoghurt and kefir (Mann 1989; Libudzisz and Piatkiewicz attention with regard to their roles during kefir manufac-
1990; Serova 1997; Zimovetz and Boyko 2000). A survey ture because of their contribution to taste; both have been
of kefir products purchased on the retail market in War- found to increase in concentration during kefir fermenta-
saw, Poland showed that 73% of products contained 107– tion. During storage, acetaldehyde increases in concentra-
109 cfu bacteria/g, and that 97% of samples were coli- ¨
tion and acetoin decreases (Guzel-Seydim et al. 2000a,
˘
¨
form-free (Molska et al. 2003). However, 48% of samples 2000b). Yuksekgag et al. (2004a), in their study of 21 iso-
did not meet FAO/WHO requirements for yeast numbers lates of lactic acid bacteria from various sources of Turk-
(FAO/WHO 2001). ish kefir, were able to show that all 21 isolates produced
acetaldehyde (0.88–4.40 mg/ml) when added to milk.
A whey beverage with an acceptable flavour has
4. Characteristics of kefir
recently been developed using kefir yeasts (Athanasiadis
et al. 2004), especially when fructose was added to fresh
The flavour, viscosity and microbial/chemical composition
milk before fermentation, and final pH of the beverage
of the final kefir product can be affected by the size of the
inoculum added to the milk, the occurrence of any agita- was 4.1. Fructose was found to increase production of sev-
tion during fermentation, and the rate, temperature and eral flavour volatiles, but did not increase fermentation
time.
duration of the cooling and ripening stages following fer-
mentation (Koroleva 1988b). Natural kefir has a refresh-
ing, yeasty taste and a ‘sparkling’ mouth feel (Kemp
5. Kefir grains
1984).
Kefir grains resemble small cauliflower florets: they mea-
Modern manufacturing procedures for kefir result in
sure 1–3 cm in length, are lobed, irregularly shaped, white
ethanol levels in the finished product of 0.01–0.1% (Koro-
to yellow-white in colour, and have a slimy but firm tex-
leva 1982), although kefir with ethanol concentrations as
`
ture (La Riviere et al. 1967; Kosikowski and Mistry 1997;
high as 0.25% have been produced from grains in the
laboratory (Kuo and Lin 1999; Simova et al. 2002; Besh- see Figure 1). Grains are kept viable by transferring them
kova et al. 2002). The amounts of ethanol and CO2 pro- daily into fresh milk and allowing them to grow for
duced during fermentation of kefir depend on the produc- approximately 20 hours; during this time, the grains will
´
have increased their mass by 25% (Halle et al. 1994).
tion conditions used. CO2 content of kefir has been said to
be ‘comparatively low’ in relation to other fermented Grains must be replicated in this way to retain their viabi-
drinks (Koroleva 1982); values of 0.85–1.05 g/l have been lity, since old and dried kefir grains have little or no abil-
`
ity to replicate (La Riviere et al. 1967). Kefir grains repli-
reported for kefir produced from kefir grains (Beshkova
et al. 2002; Simova et al. 2002) and 1.7 g/l for kefir pro-
duced from purified cultures (Gobbetti et al. 1990) How-
ever, the generation of CO2 during kefir manufacture,
especially after packaging, presents some practical pro-
blems, since the microorganisms (particularly yeasts) in
the kefir continue to grow following packaging. The con-
tainer used to package kefir must therefore be either strong
enough to withstand any pressure build up (e.g. glass) or
flexible enough to contain the volume of gas produced
(e.g. plastic with an aluminium foil top (Kwak et al.
1996).
The distinctive taste of kefir results from the presence
of several flavour compounds which are produced during
fermentation (Beshkova et al. 2003). Kefir produced from
pure cultures did not receive high sensory evaluation
scores in Canada unless it was sweetened (Duitschaever
et al. 1987, 1991); Duitschaever et al. (1987) also showed
that only about 40% of people tasting natural kefir for the
first time gave it a positive taste rating. Addition of peach Figure 1. Kefir grains. Reproduced with permission from
flavour, or modification of the fermentation process (e.g. Handbook of Fermented Functional Foods, Farnworth,
E.R. editor. Copyright CRC Press.
addition of lactococci, lactobacilli or yeasts) increased the
Kefir – a complex probiotic E.R. Farnworth
4
Table 2. Microorganisms* in kefir grains, mother
culture and kefir drink
Lactococci Lactobacilli Yeasts
Kefir grains 7.37 8.94 8.30
Mother culture 8.43 7.65 5.58
(wash of grains)
Kefir drink 8.54 7.45 5.24
*log CFU/g
1967; Koroleva et al. 1978). Analysis has shown that the
microbial profiles of the grains themselves, a percolate
taken from the grains (mother culture), and the final pro-
duct are not the same (see Table 2). This, in part, explains
why production of kefir must start with kefir grains, since
Figure 2. Electron micrograph of a kefir grain.
the final drink does not have the number or complexity of
microorganisms as the grains, preventing the drink from
cated in milk ‘at home with daily changes of milk’ and
being used as a starter culture for a new batch of kefir.
stored for three months either at room temperature or at
Kandler and Kunath (1983) reported similar results when
48C had microbiological profiles that were different to
they compared the microflora of kefir, inoculated milk
those of fresh grains (Pintado et al. 1996). In addition,
before incubation, and a mixture of kefir grains.
washing grains in water also reduced viability. It has been
recommended that in a commercial operation using grains
to produce kefir, grains should be kept viable through
6. Microbiology of kefir grains
daily transfers and should only be replaced if their ability
to ferment milk becomes impaired. (Koroleva 1982). Low
6.1 Bacteria
temperature storage appears to be the best way to maintain
kefir grains for long periods. Garrote et al. (1997) showed The microbial population found in kefir grains has been
that storage of kefir grains at À80 or À208C for 120 days used as an example of a symbiotic community (Margulis
did not change their fermentation properties compared to 1995); this symbiotic nature has made identification and
grains that had not been stored; however, grains stored at study of the constituent microorganisms within kefir grains
À48C did not produce acceptable kefir after thawing. Kefir difficult. Koroleva (1991) stated that kefir bacteria and
grains replicated in soy milk have been reported to be yeasts, when separated as pure cultures, either do not grow
smaller in size compared to grains replicated in cows’ in milk or have a decreased biochemical activity, which
milk (Liu et al. 2002). There have been no reports of suc- further complicates the study of the microbial population
cessful production of kefir grains from pure cultures. of kefir grains. Several media have been proposed for the
While early studies of kefir grains employed light isolation and identification of bacteria in kefir grains
microscopy, later investigations used electron microscopy (Kojima et al. 1993). Linossier and Dousset (1994)
to describe the complex microbial community of which showed that Lactobacillus kefir grew better when the yeast
they were comprised (Ottogalli et al. 1973; Bottazzi and Candida kefir was added to the milk. Garrote et al. (2004)
Bianchi 1980; Molska et al. 1980; Marshall et al. 1984; reported a similar observation when they attempted to
Duitschaever et al. 1988b; Toba et al. 1990; Neve 1992; grow L. kefir in milk. In general, lactic acid bacteria are
more numerous (108–109) than yeasts (105–106) and acetic
Bottazzi et al. 1994; Rea et al. 1996). Figure 2 shows an
acid bacteria (105–106) in kefir grains, although fermenta-
electron micrograph of kefir grains obtained from the
Moscow Dairy Institute. Ottogalli et al. (1973) showed tion conditions can affect this pattern (Koroleva 1991;
that the chemical and microbiological compositions of Garrote et al. 2001) Table 3 shows a list of the various
kefir grains from four different sources were different, bacteria that have been reported in kefir and kefir grains
making comparisons between results published by differ- from around the world.
ent laboratories difficult. Garrote et al. (2004) carried out several in vitro tests to
The microbial population that makes up kefir grains try to explain how the bacteria in kefir grains function.
appears to be relatively constant over time, although sea- They showed that two of the heterofermentative lactoba-
sonal variations in the grain flora have been noted which cilli, L. kefir and L. parakefir, possessed S-layer proteins
`
can affect the final product consistency (La Riviere et al. that can be used to explain in part their auto-aggregation
Kefir – a complex probiotic E.R. Farnworth 5
the yeasts in kefir grains provide an environment for the
Table 3. Bacteria found in kefir grains and kefir
growth of kefir bacteria, producing metabolites that contri-
Lactobacilli bute to the flavour and mouthfeel of kefir (Clementi et al.
kefir a,c,j,n,o,p,r Lactobacillus delbrueckii a,h,p
Lactobacillus
1989; Kwak et al. 1996; Simova et al. 2002). Table 4 lists
kefiranofaciens l,n,p Lactobacillus rhamnosus a,r
Lactobacillus
the various yeasts that have been reported in kefir grains.
kefirgranum n Lactobacillus casei h
Lactobacillus
To prevent excessive CO2 production (particularly after
parakefir n,o Lactobacilli paracasei p
Lactobacillus fermentation), Kwak et al. (1996) suggested a two stage
brevis g,h,p,r Lactobacillus fructivorans k
Lactobacillus fermentation process starting with a non-lactose ferment-
plantarum o,p Lactobacillus hilgardii k
Lactobacillus ing yeast such as Saccharomyces cerevisiae.
helveticus a,b,h Lactobacillus fermentum r
Lactobacillus The properties of yeasts found in kefir grains vary. For
acidophilus g,p,r Lactobacillus viridescens r example, some of the yeasts found in kefir grains are cap-
Lactobacillus
able of fermenting lactose, while some are not. Also, it
Lactococci
has been observed that some types of yeasts are located at
Lactococcus lactis subsp. lactis a,c,e,f,g,h,k,o,r
the surface of the grain, while others inhabit the interior.
Lactococcus lactis subsp. cremoris a,e,f
It may be that yeasts located at different locations in the
Streptococci kefir grains play different roles in the fermentation pro-
Streptococcus thermophilus e,h cess. (Iwasawa et al. 1982; Wyder et al. 1997). Iwasawa
et al. (1982) showed that the electrophoretic pattern of the
Enterococci
yeast Torulopsis holmii isolated from Danish kefir grains
**
Enterococcus durans d ,e
demonstrated patterns indicating the presence of ten differ-
(reported as Streptobacterium durans in ref. d; reported as
Streptococcus durans in ref. e) ent enzymes. Wyder et al. (1997) used restriction analysis
of the two ITS regions to show that yeasts from five kefir
Leuconostocs
grain samples of different origins had unique patterns,
Leuconostoc sp. r
indicating the presence of different yeast species in kefir
*
Leuconostoc mesenteroides a,b,g ,o
grains from different origins. Like kefir bacteria, the pro-
(reported as Leuconostoc kefir in ref. g)
file of yeasts is different in kefir grains when compared to
Acetic acid bacteria
the final kefir product (Wyder et al. 1997). Abraham and
Acetobacter sp. o De Antoni (1999) showed that the yeast population in
*
Acetobacter pasteurianus g kefir produced from cows’ milk using grains was two logs
(reported as Acetobacter rancens in ref. g)
higher than when the same grains were added to soy milk.
Acetobacter aceti a,d
Other bacteria
7. Other uses of kefir grains
Bacillus sp. r Micrococcus sp. r
Bacillus subtilis g Escherichia coli r The ability of kefir grains to grow in milk whey prompted
Rimada and Abraham (2001) to study whether kefir grains
a b c d
Koreleva 1991; Lin et al. 1999; Pintado et al. 1996; Rosi 1978; ref.
could be added to whey produced as a by-product of the
e f g
¨
Yuksekdag et al. 2004; Dousset and Caillet 1993; Ottogalli et al. 1973;
dairy industry in Argentina, thereby producing a value-
h j k
Simova et al. 2002; Kandler and Kunath 1983; Yoshida and Toyoshima
l n o
1994; Fujisawa et al. 1988; Takizawa et al. 1994; Garrote et al. 2001; added product called kefiran. Kefiran was produced at a
p r
Santos et al. 2003; Angulo et al. 1993.
rate of 103 mg/l following fermentation at 438C for 120 h,
with an inoculation rate of 100 g grains per litre of milk.
Athanasiadis et al. (1999) showed that kefir yeast cells
and haemagglutination properties. In addition, these
that had been immobilized on de-lignified cellulose were
two bacteria were also shown to adhere to Caco-2 cells,
capable of producing commercially important quantities of
raising the possibility that these bacteria would be good
ethanol from glucose over a wide variety of temperatures
probiotics.
(5–308C). Production of volatiles (e.g. ethanal, ethyl acet-
ate, propanol-1, isobutyl alcohol and amyl alcohols) was
found to depend on fermentation temperature. Ethyl acet-
6.2 Yeasts
ate content did not change as fermentation temperature
It has been recognized that yeasts play an important role decreased, although contents of total volatiles during fer-
in the preparation of fermented dairy products, where they mentations at 58C were 38% of those carried out at 308C.
can provide essential growth nutrients such as amino acids Using this system, it was shown that glucose produced the
and vitamins, alter the pH, secrete ethanol and produce fastest fermentation compared to fructose or sucrose,
CO2 (Viljoen 2001). The yeasts in kefir have been less although glucose-based fermentations also yielded lower
well studied than kefir bacteria, although it is obvious that concentrations of amyl alcohols, ethyl acetate and ethanol
Kefir – a complex probiotic E.R. Farnworth
6
Table 4. Yeasts found in kefir grains and kefir Table 5. Definitions of functional foods and probiotics
* *
Kluyveromyces marxianus a,b,f ,g,h,i,j,k,m ,n Candida friedrichii n Functional foods
(reported as Saccharomyces lactis in A functional food is one that is consumed as part of a usual diet,
ref. f; reported as Kluyveromyces lactis and is demonstrated to have physiological benefits and/or reduce
in ref. m) the risk of chronic disease beyond basic nutritional functions.
Saccharomyces sp. k Candida (Health Canada 2004)
pseudotropicalis f
Probiotics
*
Saccharomyces cerevisiae a,d,e,f ,g,j,m,n Candida tenuis f
Live microorganisms that, when administered in adequate
(reported as Saccharomyces carlbergensis
amounts, confer a health benefit on the host. (FAO/WHO 2002).
in ref. f)
Report of a Joint FAO/WHO Working Group, ‘Guidelines for
Saccharomyces unisporus c,h,j,m Candida the Evaluation of Probiotics in Food’, London, Ontario, Canada,
inconspicua g 2002.
*
Saccharomyces exiguus l Candida maris g
(reported as Torolopsis holmii in ref. l)
Saccharomyces turicensis h Candida lambica j (1982b) who reported decreases in biotin, vitamin B12 and
Saccharomyces delbrueckii d Candida pyridoxine, and significant increases in folic acid, as com-
tannotelerans e pared to non-fermented milk.
Saccharomyces dairensis n Candida valida 6 e
Torulaspora delbrueckii a,h,m Candida kefyr a,j,n
9. Bioactive ingredients in kefir
Brettanomyces anomalus h Candida holmii j,m
Issatchenkia occidentalis j Pichia The area of functional foods (see Table 5 for definition)
fermentans b,m,n has attracted a great deal of interest since it is now recog-
nized that many foods contain bioactive ingredients which
a b c d e
Koreleva 1991; Lin et al. 1999; Pintado et al. 1996; Rosi 1978; Dous-
g h
offer health benefits or disease resistance. A subset of
set and Caillet 1993; ref. fOttogalli et al. 1973; Simova et al. 2002; Wyder
i j
and Puhan 1997, 1999; Yoshida and Toyoshima 1994; Engel et al. 1986; functional foods is probiotic foods, from which there are
k m n
Garrote et al. 2001; ref. lIwasawa et al. 1982; Angulo et al. 1993; Rohm
several possible sources of bioactive ingredients. The
et al. 1992
microorganisms themselves (dead or alive), metabolites of
the microorganisms formed during fermentation (including
(Athanasiadis et al. 2001). The de-lignified cellulose mate-
antibiotics or bactericides), or breakdown products of the
rial supporting kefir yeast cells were able to ferment a
food matrix, such as peptides, may be responsible for
mixture of whey and raisins to produce a fermented pro-
these beneficial effects (Ouwehand and Salminen 1998;
duct with an alcohol content of 4.4% v/v.
Farnworth 2002; see Figure 3). Kefir has a long tradition
of offering health benefits, especially in eastern Europe
8. Composition of kefir ´
(Halle et al. 1994). There are several compounds in kefir
that may have bioactive properties.
The composition of kefir depends greatly on the type of
milk that was fermented (Kneifel and Mayer 1991). How-
ever, during the fermentation, changes in composition of
9.1 Exopolysaccharides
nutrients and other ingredients have also been shown to
occur. (Bottazzi et al. 1994). L(þ) lactic acid is the Exopolysaccharides of differing structures and composi-
tions are produced by a variety of lactic acid bacteria
organic acid in highest concentrations after fermentation
including Lactobacillus, Streptococcus, Lactococcus and
and is derived from approximately 25% of the original
Leuconostoc (De Vuyst and Degeest 1999; Ruas-Madiedo
lactose in the starter milk (Alm 1982d; Dousset and Cail-
et al. 2002.). These cell-surface carbohydrates confer pro-
let 1993). The amino acids valine, leucine, lysine and ser-
tective and adaptive properties on their bacterial produ-
ine are formed during fermentation, while the quantities of
cers; since they are often loosely bound to the cell mem-
alanine and aspartic acid increase when compared to raw
milk (Alm 1982e). Bottazzi et al. (1994) reported the brane, they are, therefore, easily lost to their environment
(Jolly et al. 2002). In food products, exopolysaccharides
occurrence of acetic acid in their kefir, although others
¨ often contribute to organoleptic and stability characteris-
reported that no acetic acid was present (Guzel-Seydim
et al. 2000a, 2000b). tics. A unique polysaccharide called kefiran has been
found in kefir grains; grains may also contain other exopo-
Kneifel and Mayer (1991) found that appreciable
lysaccharides.
amounts of pyridoxine, vitamin B12, folic acid and biotin
Kefiran contains D-glucose and D-galactose only in a
were synthesized during kefir production, depending on
ratio of 1:1. Hydrolysis reactions followed by NMR ana-
the source of kefir grains used, while thiamine and ribofla-
lyses have been used to determine the chemical structure
vin levels were reduced. These results contrast with Alm
Kefir – a complex probiotic E.R. Farnworth 7
exopolysaccharides in different media (Grobben et al.
Probiotic
1995; Van Geel-Schutten et al. 1999). Furthermore, Santos
(Kefir) et al. (2003) recently reported that they have also isolated
an exopolysaccharide closely related to kefiran.
Kefiran dissolves slowly in cold water and quickly in
hot water, and forms a viscous solution at 2% concentra-
Fermentation Bacteria, Yeasts Metabolites
´
tion (La Riviere et al. 1967). Carboxymethyl kefiran has a
Products
viscosity that is 14 times that of kefiran, although this is
still much lower than those of other thickening agents
used in the food industry, thus limiting any practical uses
of kefiran or carboxymethyl kefiran (Mukai et al. 1990).
Intestinal Microbial Digestion, Metabolism,
Kefiran can form weak gels when added to k-carrageenan
Population Immune Status,
Disease Resistance (1% 1:4 kefiran/k-carrageenan), which have gelation tem-
peratures and melting temperatures similar to those of
Figure 3. Probiotic effects on metabolism and health.
guar/k-carrageenan gels (Pintado et al. 1996).
Since its initial isolation, it has been reported that
kefiran may be produced by a variety of bacteria isolated
of kefiran (see Figure 4). The proposed structure is a
from kefir grains which have been obtained from several
branched hexa- or heptasaccharide repeating unit that is
´
sources (La Riviere and Kooiman 1967; Toba et al. 1987;
itself composed of a regular pentasaccharide unit to which
Mukai et al. 1990; Hosono et al. 1990; Yokoi et al. 1991;
one or two sugar residues are randomly linked (Kooiman
Pintado et al. 1996; Mitsue et al. 1999; Micheli et al.
1968; Micheli et al. 1999). Subsequent methylation/hydro-
1999; Santos et al. 2003). Whether in fact the bacteria
lysis studies have shown that the structure of kefiran may
reported are the same has not been studied, nor has any
be more complex than first thought (Mukai et al. 1988;
definitive identification been published to fully character-
Mukai et al. 1990). Methylation and NMR analyses have
ize those bacteria reported as kefiran producers.
also been used to verify the production of kefiran by new
Bacteria which produce exopolysaccharides are often
bacterial strains (Yokoi et al. 1991). A closer examination
found in milk or milk products, although studies have
of chemical data published by Mukai et al. (1990) raises
shown that maximum production of exopolysaccharide
the question if, in fact, two exopolysaccharides are being
may occur in chemically defined media (containing a
produced that have very similar chemical structure and
´ carbohydrate source, mineral salts, amino acids/peptides,
properties. La Riviere et al. (1967) reported that their
vitamins and nucleic acids) at a constant pH (Mozzi
kefiran had a 1:1 glucose to galactose ratio and an optical
rotation of þ68.08, while Mukai et al. (1990) isolated a et al. 1996; Dupont et al. 2000). The potential health
properties of kefiran have prompted several groups to
kefiran with a glucose to galactose ratio of 0.9:1.1 and an
optical rotation of þ548. Examples can be found in the lit- develop media and growing conditions that optimize
kefiran production (Toba et al. 1987; Yokoi et al. 1990;
erature where the same bacterial strain produced different
→ 6)-β-D-Gp-{1→2(6)}-β-D-Galp-(1→4)-α-D-Galp-(1→3)-β -D-Galp-(1→4)-β-D-Gp-(1
6(2)
↑
21
1
β-D-Gp
Figure 4. Proposed chemical structure of kefiran. Reprinted from Carbohydrate Research 7, Kooiman, P. The chemical
structure of kefiran, the water-soluble polysaccharide of the kefir grain, pp 200–211. Copyright 1968 with permission
from Elsevier.
8
Delta O.D. /cfu/ml(x10-12)
8
IM
Lc. lactis
7
6
5
4
3
2
1
0
10
1
IM
10
5
IM
00
2
IM
00
5
IM
00
8
IM
01
1
IM
02
2
IM
02
3
IM
01
4
IM
01
5
IM
08
2
Kefir – a complex probiotic E.R. Farnworth
Lb. kefirgranum
Lb. helveticus
Lb. kefir
Ln. mesenteroides
Lc. cremoris (Prt-)
Kefir Strains Reference Strains
Figure 5. Proteinase activity of bacteria from kefir and kefir grains.
9.2 Bioactive peptides
Yokoi and Watanabe 1992; Micheli et al. 1999; Mitsue
et al. 1999). Media based on lactic acid whey have been
Many organisms possess enzymes (e.g. proteinases and
found to be optimum for kefiran production. A batch
peptidases) that are able to hydrolyse the protein in a med-
procedure using a modified MRS media (MRSL) was
ium, thereby supporting growth of the organism by liberat-
reported by Micheli et al. 1999 to produce consistent
ing peptides and amino acids (Thomas and Pritchard
yields of 2 g/l of kefiran. The best kefiran yields, how-
1987; Matar et al. 1996). The action of proteinase and
ever, have been reported by Mitsue et al. (1999) when
peptidase enzymes on milk proteins can theoretically
they combined the kefiran producing bacterium, Lactoba-
result in a very large number of possible peptides. An ana-
cillus kefiranofaciens, with the yeast Torulaspora del-
lysis of the proteinase activity of kefir grain bacterial iso-
brueckii. When these two organisms were grown in a 50
lates has shown that several isolates have high proteinase
l fermentor in a fed-batch protocol, a yield of 3740 mg/l
activities (see Figure 5), which increases the possibility
was obtained over a 7 day period.
that bioactive peptides may be present in kefir. In their
No measurements have been reported with regard to
˘
¨
study of lactic acid bacteria in Turkish kefir, Yuksekdag
kefiran concentration in the final kefir product. However,
et al. (2004b) showed that 13 out of 21 lactococci strains
a comparison of the carbohydrate content of milk
had measurable proteolytic activity.
(USDA 2004) and that of kefir shows a more than dou-
Initial studies on the peptide content of kefir drink have
bling of the carbohydrate content; how much of this is
shown that kefir contains a large number of peptides and
kefiran is not known. Abraham and De Antoni (1999)
that the majority of kefir peptides have molecular weights
did show that the polysaccharide content of kefir from
of 5000 kDa (Farnworth 2005, unpublished results).
cows’ milk was almost twice that of kefir produced
from soy milk.
Kefir grains grown in soy milk produce an exopolysac-
10. Health benefits of kefir
charide that Liu et al. (2002) have shown to be primarily
composed of D-glucose and D-galactose (ratio 1.00: 0.43), Kefir has had a long history of being beneficial to health
with a molecular weight of approximately 1.7 Â 106 Da. in Eastern European countries, where it is associated with
Kefir – a complex probiotic E.R. Farnworth 9
general wellbeing. It is easily digested (Alm 1982c) and is the polysaccharide stimulated PP cells, causing them to
often the first weaning food received by babies. Many of secrete water-soluble factors that, in turn, enhanced the
the studies regarding health benefits of kefir have been mitogenic response of thymocytes and splenocytes in nor-
published in Russian and Eastern European journals and mal mice.
therefore are not easily accessible to Western science
(Batinkov 1971; Ormisson and Soo 1976; Evenshtein
10.2 Inhibition of tumour growth
1978; Safonova et al. 1979; Ivanova et al. 1981; Sukhov
et al. 1986; Besednova et al. 1997; Oleinichenko et al. Shiomi et al. (1982) were the first to report the antitumour
effects of a water-soluble polysaccharide (approximate
1999). However, the health benefits of kefir were demon-
molecular weight 1 000 000 Da) isolated from kefir grains.
strated in Canada as early as 1932 (Rosell 1932).
Whether given orally or intraperitoneally, the polysacchar-
ide was able to inhibit the growth of Ehrlich carcinoma or
10.1 Stimulation of the immune system
Sarcoma 180 compared to control mice receiving no kefir-
derived polysaccharide (Shiomi et al. 1982; Murofushi
It has been proposed that stimulation of the immune sys-
et al. 1983). The mechanism of action was not clear, since
tem may be one mechanism whereby probiotic bacteria
in vitro incubation of the two cancer cell lines with the
may exert many of their beneficial effects (De Simone
et al. 1991; Gill 1998); this may be a direct effect of the polysaccharide showed low cytotoxicity during 42 hours of
bacteria themselves (Cross 2002). However, peptides incubation. This group then went on to show that this
formed during the fermentation process or during diges- water-soluble polysaccharide was able to reach the spleen
tion have also been shown to be bioactive, and demon- and thymus of mice and, based on the response to thymus-
strate a variety of physiological activities, including stimu- dependent and thymus-independent antigens, concluded
lation of the immune system in animal models (LeBlanc that oral immune enhancement was mediated through T-
et al. 2002; Matar et al. 2003). cell, but not B-cell activity. (Murofushi et al. 1986). More
Thoreux and Schmucker (2001) fed kefir produced from recently, a water soluble polysaccharide fraction from kefir
grains to young (6 months) and old (26 months) rats and grains was shown to inhibit pulmonary metastasis of Lewis
found an enhanced mucosal immune response in the lung carcinoma, whether the kefir-derived polysaccharide
young animals, as shown by a higher anti-cholera toxin was given orally before or after tumour transplantation.
Murofushi et al. (1983) also reported the antitumour effec-
(CT) IgA response compared to controls. Both young and
old rats had significantly increased total non-specific IgG tiveness of kefir grain polysaccharides regardless of the
blood levels, and a decreased systemic IgG response to time of administration, although they cautioned that larger
CT. Taken together, Thoreux and Schmucker concluded doses may only be more effective if administered after
that kefir, like other probiotics, was exerting an adjuvant establishment of the tumours. A water-insoluble fraction
effect on the mucosal immune system, perhaps produced containing kefir grain microorganisms, rather than the
by bacterial cell wall components. water-soluble polysaccharide fraction, significantly inhib-
Stimulation of the immune system may also occur due ited metastasis of highly colonized B16 melanoma. (Furu-
kawa et al. 1993; Furukawa et al. 2000). It was suggested
to the action of exopolysaccharides found in kefir grains.
Murofushi et al. (1983, 1986) used the method of La Riv- that the water-soluble polysaccharide suppressed tumour
´
iere et al. (1967) for the extraction of kefiran from kefir growth by means of the lymphokine activated macrophage
grains to produce a water-soluble polysaccharide fraction (Mf) via the gut-associated lymphoid tissue, while the
that they fed to mice. The reduction in tumour growth that water-insoluble microorganism fraction acted through an
they observed was linked to a cell-mediated response, and increase of NK cell activity.
it appeared that the total dose of the polysaccharide deter- Feeding kefir itself (2 g/kg body weight by intubation)
mined its effectiveness. Furukawa et al. (1992) have also was more effective in inhibiting tumour (Lewis lung carci-
shown that a water-soluble fraction of kefir grains may act noma) growth than yoghurt, when given for 9 days after
tumour inoculation (Furukawa et al. 1990). It was also
as a modulator of the immune response.
The effect of kefir exopolysaccharides on the immune shown that mice receiving kefir had an improved delayed-
system may be dependent on whether the host is healthy type hypersensitivity response compared to tumour-bearing
or has developed any tumours. Furukawa et al. (1996) mice receiving no kefir, although the mean survival time
was not affected (Furukawa et al. 1991). Kubo et al.
incubated kefir grain polysaccharides with Peyer’s Patch
(PP) cells from tumour-bearing mice and found that the (1992) also reported that feeding kefir (100–500 mg/kg
supernatant of this mixture enhanced proliferation of sple- body weight) inhibited the proliferation of Ehrlich ascites
nocytes from normal mice and increased the mitogenic carcinoma. In addition, kefir, from which the grains had
activities of lipopolysaccharides (LPS) and phytohaemag- been removed by filtration, were shown to kill or arrest
glutinin-P (PHA-P) in splenocytes. They concluded that the growth of fusiform cell sarcomas induced by 7,12-
Kefir – a complex probiotic E.R. Farnworth
10
10.3 Kefir and lactose intolerance
dimethylbenzanthracene in mice when the kefir was
injected intraperitoneally (Cevikbas et al. 1994). Examina-
A proportion of the global population is unable to digest
tion of tissue in kefir-treated mice showed a small amount
lactose (the major sugar found in milk), because of insuffi-
of mitosis, some stromal connections and, in some cases,
cient intestinal b-galactosidase (or lactase) activity (Alm
disappearance of tumour necrosis.
1982a). Research has shown, however, that lactose maldi-
Hosono et al. (1990) showed that isolates of Streptococ-
gestors are able to tolerate yoghurt, providing the number
cus, Lactobacillus and Leuconostoc in Mongolian kefir all
of live bacteria present in the yoghurt consumed is high
showed strong in vitro binding to amino acid pyrolysates
enough (Pelletier et al. 2001). It is believed that the bac-
which are believed to be mutagens and are commonly
teria in the yoghurt matrix are protected by the buffering
found in food. Similarly, Miyamoto et al. (1991) reported
effect of the yoghurt. Bacterial cells remain viable, and
that three slime-producing strains of Streptococcus lactis
the bacterial cell walls remain intact, and thus the b-galac-
subsp. cremoris found in German kefir had strong desmu-
tosidase enzyme contained in the yoghurt-producing bac-
tagenic properties, which they attributed to the ability of
teria (L. acidophilus) is protected during transit through
such strains to bind to a known mutagen. Using an Ames
the stomach until it arrives at the upper gastrointestinal
test, Yoon et al. (1999) showed that Lactobacillus spp.
tract (Montes et al. 1995; De Vrese et al. 2001). It has
isolated from kefir and yoghurt had antimutagenic proper-
also been shown that fermented milk products have a
ties against the mutagen 2-nitrofluorene.
slower transit time than milk, which may further improve
Liu et al. (2002) studied the effects of soy milk and
lactose digestion (Vesa et al. 1996; Labayen et al. 2001).
cows’ milk fermented with kefir grains on the growth of
Some kefir grains have been shown to possess b-galac-
tumours in mice, using freeze-dried kefir (produced from
tosidase activity which remains active when consumed
either soy or cows’ milk) from which the grains had been
(De Vrese et al. 1992). A recent study has shown that a
removed following fermentation. Mice were injected with
commercial kefir produced using a starter culture contain-
0.2 Â 108 Sarcoma 180 cells one week prior to the start
ing six bacteria (but not L. acidophilus) and one yeast was
of the feeding portion of the experiment. Tumour growth
equally as effective as yoghurt in reducing breath hydro-
(volume) was estimated for up to 30 days, after which
gen in adult lactose maldigestors (Hertzler and Clancy
tumours were removed and weighed. Both soy milk kefir
2003). Severity of flatulence in this group was also
(À70.9%) and cows’ milk kefir (À64.8%) significantly
reduced when either yoghurt or kefir was consumed com-
inhibited tumour growth, compared to mice in the positive
pared to milk.
control group. Microscopic examination of the tumours
De Vrese et al. (1992) showed that when pigs were fed
indicated that apoptosis may have been responsible for
kefir containing fresh grains, their plasma galactose con-
reduced tumour growth. Similar effects of yoghurt on
centrations rose significantly higher than pigs given kefir
apoptosis have been reported (Rachid et al. 2002). Mice
containing heated grains. The diet containing kefir and
fed unfermented soy milk did not have reduced tumour
fresh grains had a b-galactosidase activity of 4.4 U/l, which
volumes at day 30, and Liu et al. (2002) concluded that
was identified as being responsible for the hydrolysis of
either the microorganisms themselves or any polysacchar-
lactose in the intestine, thus yielding galactose that can be
ides formed during fermentation by the kefir grains micro-
absorbed. Kefir itself contains no galactose (Alm 1982).
flora were responsible for the antitumour response. Genis-
tein itself has been shown to inhibit tumours (Murrill
et al. 1996; Constantinou et al. 1996), although in this
10.4 Antimicrobial properties of kefir
study genistein levels did not change during the fermenta-
There are data to show that many lactobacilli are capable
tion process. Mice consuming kefir samples also had sig-
nificantly increased levels of IgA in their small intestines of producing a wide range of antimicrobial compounds,
compared to control animals, and it was proposed that the including organic acids (lactic and acetic acids), carbon
dioxide, hydrogen peroxide, ethanol, diacetyl and peptides
PP tissue was increasing IgA secretion into the intestine in
(bacteriocins) that may be beneficial not only in the reduc-
response to food antigens.
¨
Guven et al. (2003) proposed an alternative suggestion tion of foodborne pathogens and spoilage bacteria during
as to how kefir may protect tissues. They showed that food production and storage, but also in the treatment and
prevention of gastrointestinal disorders and vaginal infec-
mice exposed to carbon tetrachloride (a hepatotoxin to
tions (Tahara and Kanatani 1997; Zamfir et al. 1999;
induce oxidative damage) and given kefir by gavage had
´
decreased levels of liver and kidney malondialdehyde, Bonade et al. 2001; Messens and De Vuyst 2002; Jamuna
indicating that kefir was acting as an antioxidant. Further- and Jeevaratnam 2004).
Garrote et al. (2000) tested the inhibitory activity of a
more, their data showed that kefir was more effective than
supernatant of cows’ milk fermented with kefir grains,
vitamin E (which is well known to have antioxidative
properties) in protecting against oxidative damage. against Gram-negative and Gram-positive bacteria. Gram-
Kefir – a complex probiotic E.R. Farnworth 11
10.5 Behaviour of kefir bacteria in the
positive microorganisms were inhibited to a greater extent
than Gram-negative microorganisms; moreover, both lactic gastrointestinal tract
and acetic acids were found in the supernatants. Garrote
One of the criteria for probiotic bacteria is that they
et al. (2000) showed that milk supplemented with lactic
should be able to withstand the harsh conditions of the
acid or lactic acid plus acetic acid at the concentrations
gastrointestinal tract, including extreme pH conditions pre-
found in the kefir supernatant also had inhibitory activity
sent in the stomach and the action of bile salts and diges-
against E. coli 3. They concluded that organic acids pro-
tive enzymes (Lee and Salminen 1995). It is also believed
duced during kefir fermentation could have important bac-
that one way in which probiotic bacteria could protect
teriostatic properties even in the early stages of milk fer-
against pathogenic bacteria would be to compete with or
mentation. Cevikbas et al. (1994) found similar results
displace pathogenic bacteria by adhering to intestinal
against Gram-positive coccus, staphylococcus, and Gram-
epithelial cells. (Kirjavainen et al. 1998; Fujiwara et al.
positive bacillus, and noted that kefir grains were more
2001; Gibson and Rastall 2003).
effective with regard to their antibacterial properties than
No results from human feeding trials have been pub-
the final kefir product.
lished with regard to the ability of the microorganisms
Kefir grains themselves have inhibitory power against
found in kefir to traverse the upper GI tract in large num-
bacteria that can be preserved during lyophilization, parti-
bers and arrive at the large intestine. Kefir, because it is
cularly when glycerol is added as a cryopreservative
milk based, is able to buffer the pH of the stomach when
(Brialy et al. 1995). Fresh kefir grains were found to inhi-
ingested and thereby provide time for many of the bacteria
bit the growth of the bacteria Streptococcus aureus, Kleb-
to pass through to the upper small intestine (Farnworth
siella pneumoniae and Escherichia coli, but not the yeasts
et al. 2003). Santos et al. (2003) isolated 58 strains of
Candida albicans and Saccharomyces cerevisiae. Leuco-
Lactobacillus spp. and isolates of L. paracasei, L. plan-
nostoc mesenteroides and Lactobacillus plantarum, iso-
tarum, L. delbrueckii, L. acidophilus and L. kefiranofa-
lated from kefir grains, have both been shown to produce
ciens from different sources of kefir grains and exposed
antimicrobial compounds that are present in kefir. Both
them to an MRS medium at pH 2.5 and MRS containing
inhibit Gram-positive and Gram-negative bacteria, have a
0.3% Oxgall (bile salts). They found that all strains sur-
molecular weight of approximately 1000 kDa and are heat
vived 4 h incubation at pH 2.5, but did not grow. Eighty-
stable, although their antimicrobial properties are reduced
five percent of isolates showed high resistance to Oxgall,
after exposure to proteolytic enzymes (Serot et al. 1990).
but had delayed growth.
Santos et al. (2003) showed that lactobacilli isolated from
The caco-2 cell assay has been used to show that many
kefir grains had antimicrobial activities against E. coli (43/
of the lactobacilli isolated from kefir grains are able to
58 strains), Listeria monocytogenes (28/58 strains), Salmo-
bind to enterocyte-like cells (Santos et al. 2003), although
nella typhimurium (10/58 strains), S. enteritidis (22/58
the authors also cautioned that results using this model
strains), S. flexneri (36/58 strains) and Yersinia enterocoli-
might not necessarily apply in vivo.
tica (47/58 strains). Bacteriocins were thought to be
Human studies of the effects of diet on intestinal micro-
responsible, although they were not identified.
flora are limited to the analysis of faecal samples,
In a study in which foodborne bacterial pathogens (E.
although no detailed human study has been published in
coli O157:H7, L. monocytogenes 4b, Y. enterocolitica 03)
which kefir has been used. Marquina et al. (2002) used
were added at the beginning of yoghurt or kefir fermenta-
mice to study the effect of consuming kefir (source not
tion, both kefir and yoghurt failed to inhibit pathogenic
defined) in a feeding study that lasted 7 months. They
bacterial growth. For kefir, this was explained as being
were able to show that the numbers of lactic acid bacteria
due to the slow acid development during fermentation.
in the mouse small and large intestines increased signifi-
Interestingly, fermentations of kefir and yoghurt combina-
cantly. Streptococci increased by 1 log, while sulfite-redu-
tions proved to be more effective at pathogen suppression
cing clostridia decreased by 2 logs.
than single fermentation (Gulmez and Guven 2003)
Hydrogen peroxide is another metabolite produced by
˘
¨
some bacteria as an antimicrobial compound. Yuksekdag
et al. (2004a) showed that all 21 isolates of lactic acid
10.6 Kefir and cholesterol metabolism
bacteria from Turkish kefir produced hydrogen peroxide
Positive effects of yoghurt consumption on cholesterol
(0.04–0.19 ug/ml). In a later paper, they reported that 11
out of 21 strains of kefir lactococci produced hydrogen metabolism have been reported (Kiessling et al. 2002;
˘
¨
peroxide (Yuksekdag et al. 2004b). All lactococci strains Xiao et al. 2003), although a review of the literature
were effective in inhibiting growth of Streptococcus aur- reveals that the results are at best moderate, and are often
inconsistent (Taylor and Williams 1998; St-Onge et al.
eus, but were less effective against E. coli NRLL B-704
and Pseudomonas aeruginosa. 2000; Pereira and Gibson 2002).
Kefir – a complex probiotic E.R. Farnworth
12
Several hypotheses have been proposed regarding the found in kefir. Furthermore, there is evidence to show that
possible mechanism of action employed by bacteria to kefir consumption not only affects digestion, but also
reduce cholesterol levels (St. Onge et al. 2002). Vujicic influences metabolism and immune function in humans.
et al. (1992) showed that kefir grains from Yugoslavia,
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