A review: chemical, microbiological and nutritional characteristics of kefir

Kefir, a mildly acidic fermented milk, is produced by the addition of lactic acid bacteria and yeasts to milk. The composition of kefir varies according to factors such as milk type and the microbiological composition of culture types (kefir grain and commercial starter culture). Kefir's distinctive flavour is a blend of lactic acid, ethanol, carbon dioxide and flavouring products, such as acetaldehyde and acetoin. The microorganisms in kefir produce vitamins, degrade protein and hydrolyse lactose, resulting in a highly nutritious and digestible foodstuff. The microbiological composition of kefir has been investigated using a wide range of microbiological and molecular approaches. The microbiological and chemical composition of kefir indicates that it is a very complex probiotic, with Lactobacillus species, generally the predominant microorganisms. Kefir is now increasingly being consumed in certain areas of the world, such as southwestern Asia, Europe, North America and Japan.