Kefir (alternately kefīrs, keefir, kephir, kewra, talai, mudu kekiya, milkkefir, búlgaros), purportedly from either the Turkish “keyif” (joy/pleasure) or “köpür” ((milk) froth, foam), is a fermented milk drink that originated with shepherds of the Caucasus region, who discovered that fresh milk carried in leather pouches would occasionally ferment into an effervescent beverage. It is prepared by inoculating cow, goat, or sheep’s milk with kefir grains. Traditional kefir was made in skin bags that were hung near a doorway; the bag would be knocked by anyone passing through the doorway to help keep the milk and kefir grains well mixed. Dairy-free alternatives are available, such as coconut milk kefir and soy milk kefir.
Kefir grains are a combination of bacteria and yeasts in a matrix of proteins, lipids, and sugars. This symbiotic matrix forms “grains” that resemble cauliflower. Many different bacteria and yeasts are found in the kefir grains, which are a complex and highly variable community of micro-organisms.
Traditional kefir is fermented at ambient temperatures, generally overnight. Fermentation of the lactose yields a sour, carbonated, slightly alcoholic beverage, with a consistency similar to thin yoghurt. Kefir fermented by small-scale dairies early in the 20th century achieved alcohol levels between 1 and 2 percent, but kefir made commercially with modern methods of production has less than 1% alcohol, possibly due to reduced fermentation time.
Variations that thrive in various other liquids exist. They may vary markedly from kefir in both appearance and microbial composition. Water kefir (or kefir d’acqua) is grown in water with sugar (sometimes with added dry fruit such as figs, and lemon juice) for a day or more at room temperature.