Kumis is a fermented dairy product traditionally made from mare's milk. It is in the category of alcoholic drink and the drink remains important to the peoples of the Central Asian steppes, of Huno-Bulgar, Turkic, and Mongol origin.
Kumis comes from the Turkic word k?m?z. K?m?z is found throughout the Turkic language family and cites the 11th-century appearance of the word in Diwan Lughat al-Turk written by Kasgarli Mahmud in the Karakhanid language.
Kumis is a dairy product similar to kefir, but is produced from a liquid starter culture, in contrast to the solid kefir "grains". Because mare's milk contains more sugars than cow's or goat's milk when fermented, kumis has a higher, though still mild, alcohol content compared to kefir.
Even in the areas of the world where kumis is popular today, mare's milk remains a very limited commodity. Industrial-scale production, therefore, generally uses cow's milk, which is richer in fat and protein, but lower in lactose than the milk from a horse. Before fermentation, the cow's milk is fortified in one of several ways. Sucrose may be added to allow a comparable fermentation. Another technique adds modified whey to better approximate the composition of mare's milk.
Kumis is made by fermenting raw unpasteurized mare's milk over the course of hours or days, often while stirring or churning. (The physical agitation has similarities to making butter). During the fermentation, lactobacilli bacteria acidify the milk, and yeasts turn it into a carbonated and mildly alcoholic drink.
Kumis itself has a very low level of alcohol, comparable to small beer, the common drink of medieval Europe that also helps to avoid the consumption of potentially contaminated water. Kumis can, however, be strengthened through freeze distillation, a technique Central Asian nomads are reported to have employed. It can also be made into the distilled beverage known as araka or arkhi.