Sour cream

Sour cream is a leaner, firmer version of crème fraîche. It contains 20% milk fat and enough protein to curdle when cooked. It appears to have originated from Central and Eastern Europe and brought to the US in the 19^th century.  Since then, Americans have added a small amount of rennet, which contains enzymes that cause protein coagulation. The result is a heavier, firmer sour cream than its European counterpart.

Acidified sour cream is made by coagulating milk with acid instead of through fermentation. It is therefore also known as non-fermented sour cream. Manufacturer versions of low fat and non-fat sour cream replace butterfat with starch, plant gum, and dried milk protein.