kefir

Kefir is a fermented milk drink produced by inoculating milk with kefir grains, a living culture comprising a symbiotic matrix of bacteria and yeasts. The grains resemble small, gelatinous pearls that ferment the lactose in milk, producing lactic acid, carbon dioxide, and small amounts of alcohol. The resulting beverage is usually mildly sour, creamy, and lightly effervescent.

Kefir grains are a complex community of lactic acid bacteria, such as Lactobacillus kefiri, Lactobacillus casei, Leuconostoc, and various species of yeasts including Kluyveromyces and Saccharomyces. They are embedded in a matrix called kefiran. Fermentation typically takes 12–48 hours at room temperature, depending on the desired tartness and thickness. Lactose is partially fermented, making kefir often tolerable for many lactose-intolerant individuals.

Kefir is a source of protein, calcium, B vitamins, and probiotics. It may contain trace amounts of alcohol due to fermentation. It is generally safe for healthy people; those with dairy allergies or sensitivities should avoid dairy kefir, though lactose intolerance is commonly cited as a reduced concern. It can be stored refrigerated after fermentation, where fermentation slows but may continue slowly.

Kefir originated in the Caucasus region and spread to Eastern Europe. Traditional methods use cow, goat, or sheep milk; plant-based milks can be used in some home cultures, but results vary. Commercial kefir is widely available. See also probiotic foods, yogurt.