sour cream

sour cream, dairy product made from fermented cream inoculated with lactic acid bacteria. The addition of bacteria results in a tart thick substance that is often used as a condiment or added to stews or soups. Like yogurt and other fermented foods, sour cream contains probiotic bacteria, which may help to alleviate gastrointestinal issues and promote overall bodily immunity. Sour cream has a high fat content and is a good source of calories.

It is thought that sour cream originated from koumiss (also spelled kumiss), a slightly alcoholic drink made from mare’s milk and first fermented by the Botai people of what is now Kazakhstan—who may have been among the first humans to tame horses. Mare’s milk has a much higher level of lactose than cow’s or yak’s milk and thus produces a strong laxative effect in humans if ingested raw. Fermentation, however, lowers the lactose to tolerable levels as the bacteria convert it to lactic acid. As domesticated horses proliferated throughout Eurasia, koumiss became a staple of the nomadic Mongolian diet. People churned the mare’s milk in large vats until bacteria produced lactic acid and wild yeasts produced alcohol and carbonation. As the Mongols conquered much of Central Asia and parts of eastern and central Europe, they spread their culture and foods. Russians took koumiss into their settled lifestyle, using cow’s milk instead of mare’s. Over time, they adjusted the fermentation process to prevent the development of alcohol, instead letting the substance thicken over a longer period of time. The resulting tangy cow’s cream—called smetana in Russian-speaking regions—spread across Europe.

In commercial sour cream production, the cream is pasteurized before fermentation to remove any microorganisms. It is then homogenized at a low temperature to disperse the milk fats evenly, giving the final product a uniform texture. American sour cream is usually thicker than European sour cream, because it undergoes the homogenization process twice instead of just once. Bacterial starter cultures are added next and often include species of Lactococcus and Leuconostoc. The enzyme rennet is sometimes added to coagulate the proteins and further thicken the cream. The mixture ripens for 14 to 16 hours at 22 °C (about 72 °F) before being chilled for 12 to 48 hours. A nonfermented type of sour cream can be made at home fairly easily, using whole milk, cream, and lemon juice or vinegar.

Modern sour cream is noted for its uniform creamy texture and decidedly tart flavor. The consistency is between that of heavy cream and that of cream cheese. Commercial sour cream usually contains between 18 percent and 20 percent butterfat (though it may contain up to 25 percent), which causes the sour cream to curdle if cooked, unlike its French counterpart, crème fraîche. Most of sour cream’s flavor derives from the bacterial production of lactic acid, though small amounts of acetic, formic, propionic, or pyruvic acid are also commonly present and help heighten the product’s tanginess. The fatty, slightly nutty flavor of sour cream can be ascribed to diacetyl, a compound commonly isolated to create a buttery taste in foods like commercial popcorn.

Sour cream is spreadable and mixes easily into other foods. As such, it is commonly used to thicken and flavor sauces, dips, and dressings or is used on its own as a condiment. In Tex-Mex cuisine, it is a cold topping for enchiladas, nachos, burritos, and other dishes. Sour cream is also a common topping for baked potatoes. As an ingredient, sour cream can be used in hot dishes, where it serves to lighten and thicken. It is regularly mixed into soups and meat stews, such as traditional dishes of central and eastern Europe like goulash and borscht, and it provides a tangy counterpoint to sweet and rich flavors. Some bakers include sour cream in batters and frostings for cakes and other pastries.