Crème fraiche is a soured cream containing about 28% butterfat and with a pH of around 4.5. It is soured with bacterial culture, but is thicker, and less sour than sour cream. Crème fraiche is produced by a process similar to that of sour cream, with the exception that no ingredients are added. Each processing step requires attention to maintain high viscosity. It can be made at home by adding a small amount of cultured buttermilk or sour cream to heavy cream, and allowing it to stand for several hours at room temperature until the bacterial cultures act on the cream.
Crème fraiche is particularly useful in finishing sauces in French cooking because it does not curdle. However, "light" crème fraiche with a low fat content curdles when heated.
Crème fraiche is a substitute for sour cream.