Kefir and Koumiss: Origin, health benefits and current status of knowledge

Milk constitutes an important ingredient of healthy balanced diet of our daily life. It is an important source of vitamins, minerals, and proteins for human nutritional requirement, hence regarded as a complete food. Throughout the world, milk and milk products are valued as natural and traditional food. However, milk is extremely perishable and many means have been adapted to preserve it. The earliest one which has been used for many thousands of years is the process of fermentation (Parveen and Hafiz 2003). Milk can be fermented by inoculating fresh milk with the appropriate bacteria and incubating it at a temperature that favors their growth. As the bacteria grow, they convert milk sugar (lactose) to lactic acid through the process of fermentation. The lactic acid generated during milk fermentation decreases the pH of milk and as a result it prevents the growth of putrefactive and/or pathogenic microorganisms that do not survive in acidic environment. Since the time immemorial the process of 401fermentation has been adapted as a tool for food preservation. With due course of time, it has been noticed that many fermented foods have better nutritional and functional values when compared to their unfermented counterparts (Hasan et al. 2014). Hence the fermentation processes have become the most popular food processing techniques for preservation of foods along and for the addition of better nutritional value (Panda et al. 2014a, 2014b). Worldwide, the known fermented milk products are yogurt, kefir, koumiss, sour cream, cheeses, etc.