As a sign of immortality Allah granted a chosen tribe the first kefyr grain and therefore the grains were called grains of the prophet. In another version of this tale the grains were given by the prophet Mohammed as a present as a sign of immortality together with the recipe of kefyr, but it was forbidden to give away the grains or the recipe otherwise the grains would lose their healing power. These tales has been used as an explanation why the preparation of kefyr was kept as a secret for so long. Even though, the history of this product is centuries old (Wouters et al. 2002) the first production of retail kefyr was made in the former USSR in the 1930s (Wyder 1998).
Kefyr originates from Caucasus in Central Asia, but has become popular in many countries especially in the Middle East. Kefyr is an acidic and mildly alcoholic fermented milk beverage with a high level of CO2. Traditional kefyr is prepared in bags from goat hides, from either cow, sheep, or goat milk inoculated with kefyr grains (Motaghi et al. 1997). Kefyr grains are white, yellowish hard granules with shape as cauliflower. They are a result of a symbiotic microflora that are encapsulated in grains made of a fibrous matrix of coagulated casein, polysaccharides, fat and lysed cells. The polysaccharides in the kefyr grains differ from other known polysaccharides and are called kefyran (Wyder 1998). The relative low temperature in the region of Caucasus where kefyr originated led to a natural selection of mesophilic yeast, lactic and acetic acid bacteria in the kefyr grains (Motaghi et al. 1997; Wyder 1998). Interactions between the microorganisms have been reported (Koroleva 1988). The yeast stimulated the growth of the lactic acid bacteria releasing vitamins and amino acids and causing an increase in pH metabolizing lactic acid (Koroleva 1988). Several different composition of the microbiota in kefyr grains has been detected. The composition depends on different cultivating techniques of the kefyr grain, which is connected to the origin and temperature of the production site (Berger et al. 1999). The origin and temperature of the production site also have influence on the development of alcohol and CO2 and then the final aroma and the viscosity of the kefyr. The main yeast species detected in Kefyr are K. marxianus, C. kefyr, S. cerevisiae, S. delbrueckii (Wouters et al. 2002). In the industrial production of kefyr consistency in quality is a must. Therefore, retail kefyr is seldom produced using kefyr grains; instead commercial kefyr cultures are based on a mixture of pure cultures isolated from kefyr grains inoculated in milk. Commercial kefyr cultures contain only yeast in very low concentration if any. Gas production by the yeast causes the package to blow and consumers seem to find swelling of the package undesirable in retail kefyr.
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