c thick sour milk

Thick sour milk, known as cultured milk or fermented milk, is a dairy product produced by the bacterial fermentation of milk, primarily using Lactobacillus species such as Lactobacillus lactis. The fermentation process acidifies the milk, causing the milk proteins (casein) to coagulate and separate from the whey, creating a thick, viscous texture with a distinctly tangy, sour flavor profile. This ingredient is distinct from yogurt in that it maintains a liquid consistency (though notably thicker than fresh milk) and has a higher acidity level. Thick sour milk products vary across regions—Eastern European cultures produce varieties like Russian kefir and Ukrainian kisloe moloko, while Nordic regions have their own traditions of filmjölk and other cultured milk preparations.

Thick sour milk serves as both a cooking ingredient and a beverage across Eastern European, Scandinavian, and Central Asian cuisines. It is commonly used as a base for baking (pancakes, quick breads, and cakes), as a marinade for meats, and as a sauce ingredient in traditional dishes. The acidity acts as a leavening agent in baked goods while contributing a characteristic tang to savory preparations. It is also consumed plain as a probiotic beverage and used in soups and stews to add richness and complexity to broths.