A question that comes up quite often is whether kefir is simply a drinkable yogurt and whether probiotic yogurt is completely different from traditional yogurt.
The short answer is no to both.
Traditional yogurt is made using two bacterial species: Streptococcus thermophilus and Lactobacillus bulgaricus . These are the classic yogurt cultures that have been used for generations.
Many people think that yogurt only becomes “probiotic” when additional bacteria are added. However, the traditional yogurt cultures themselves are live microorganisms and have documented benefits, including helping improve lactose digestion in people who have difficulty digesting lactose.
Probiotic yogurts usually contain the traditional yogurt cultures plus additional species such as Lactobacillus acidophilus , Bifidobacterium , L. rhamnosus , L. reuteri , or others. In practice, the difference is often that probiotic yogurts contain more bacterial species rather than being a completely different food.
Kefir is where things become more interesting.
Unlike yogurt, traditional kefir is not purely a bacterial fermentation. It involves both lactic acid bacteria and yeasts working together.
This mixed fermentation is one of the reasons kefir develops a different flavour profile from yogurt. However, it is worth pointing out that kefir is not always more sour than yogurt. Some yogurts can be surprisingly sharp, while some kefirs can be very mild and creamy.
The presence of yeasts is one of the key characteristics that distinguishes traditional kefir from yogurt.
Another area that often causes confusion is texture.
Many products are marketed as drinkable kefir, yogurt kefir, or kefir yogurt. If you look at some ingredient lists, however, you may find only traditional yogurt bacteria and no declared yeasts.
This raises an interesting question.
If a fermented milk is drinkable but contains only yogurt bacteria, would you consider it kefir or simply a drinkable yogurt?
Traditionally, kefir has been defined by the mixed bacterial and yeast fermentation rather than by its thickness. A yogurt can be thick or drinkable. A kefir can be thin or surprisingly thick. Texture alone does not tell the whole story.
The discussion becomes even more interesting when we look at kefir grains.
Modern research suggests that kefir grains are built by the microorganisms themselves. The bacteria and yeasts produce the proteins and polysaccharides that form the grain matrix. Researchers have even demonstrated that grain-like structures can be recreated from microorganisms isolated from kefir grains.
This may help explain why some people observe grain-like aggregates gradually appearing after repeated reculturing of freeze-dried kefir starters.
What are your thoughts?
- Do you consider traditional yogurt probiotic?
- Is the presence of yeasts essential for a product to be called kefir?
- Have you seen grain-like structures develop from a freeze-dried kefir starter?
- Do you think texture is given too much importance when people compare yogurt and kefir?
References
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2010). Scientific Opinion on Live Yoghurt Cultures and Improved Lactose Digestion.
- Guarner, F. et al. (2005). Should Yoghurt Cultures Be Considered Probiotic? British Journal of Nutrition.
- Prado, M.R. et al. (2015). Milk Kefir: Composition, Microbial Cultures, Biological Activities and Related Products.
- Bourrie, B.C.T., Willing, B.P. & Cotter, P.D. (2016). The Microbiota and Health Promoting Characteristics of Kefir.
- Georgalaki, M. et al. (2021). Lactobacillus kefiranofaciens: From Isolation and Taxonomy to Probiotic Properties.
- Fan, D. et al. (2022). Microbiome and Metabiotic Properties of Kefir Grains.