Sour cream has long been a traditional ingredient in Eastern European cooking, and is an important ingredient in Hungarian cooking. It gives the pleasant tang to a great many dishes and has gained popularity in the rest of Europe, North America, and other parts of the world in the past 50 years or so. Traditionally made by letting fresh cream sour nowadays, commercially produced sour cream is made by adding bacteria cultures to cream , allowing the bacteria grow until the cream is both soured and thick, and then pasteurising it to stop the process. By definition, sour cream must contain at least 18% milk fat by weight. Sour cream is widely used in dips, spreads, sauces, cakes, soufflÃ©s, in savoury dishes such as beef stroganoff and Hungarian goulash and of course, to top baked potatoes and whilst it is rather rich in taste, it is actually lower in calories than comparable amounts of salad oils and most salad dressings. Refrigerated in the original unopened package, the shelf life of sour cream is about four weeks. After opening it will keep for up to 7 days. Should separation occur, just stir to regain a smooth consistency. Freezing is not recommended. Sour cream cannot be made at home with pasteurized cream due to the lack of natural bacteria which will cause the cream to spoil instead of sour.