Sour Cream

Manufactured sour cream is prepared by mixing milk fat and skim milk with nonfat solids and other ingredients. The mixture is then pasteurized, inoculated with lactic acid–producing bacteria, and allowed to set. Because of the texture, many beginning cooks assume that sour cream is as rich as heavy cream and can be used in the same way. Sour cream contains less butterfat than heavy cream (about 18 percent versus 35 percent) and is a much less stable emulsion. For this reason sour cream cannot be reduced or even boiled, or it will curdle. A large number of recipes—of mostly Eastern European origin—finish stews and sauces with sour cream (such as beef Stroganoff). When finishing a sauce with sour cream, make sure the sauce base is overly thick before adding the sour cream, which will thin it. A too-thick sauce can easily be thinned, but once the sour cream has been added, no further reduction is possible.