What is Kumis (or Koumiss)?

Kumis (also spelled kumiss or koumiss or kumys) is a product of fermenting milk. Traditionally it is made with mare's milk, but because of the limited availability of mare's milk, cow's milk is commonly used.

The drink is culturally important to peoples of the Central Asian steppe, including Mongols, Kazakhs, Bashkirs, Kalmyks and others. Kumis is made by fermenting raw mare's milk while stirring or churning. During the fermentation, bacteria acidify the milk, and yeasts turn it into an alcoholic drink with carbonation. Traditionally, this fermentation took place in horse-hide containers, which might be left on the top of a tent and turned over occasionally, or strapped to a saddle and agitated while riding. A vat or barrel may also be used in place of a hide container.

Early accounts of kumis comes from Herodotus describing in the 5th century B.C. Scythians using mare's milk to produce a beverage. The 13th-century explorer William of Rubrick also described the production of kumis (or termed cosmos in William's writings) while traveling through the Mongol Empire.