buttermilk

Buttermilk is a fermented dairy product. Traditionally, it was the liquid left behind after churning butter out of cultured cream. As most modern butter is not made with cultured cream but sweet cream, i.e. uncultured, most modern buttermilk is cultured. Buttermilk can be drunk straight, and it can also be used in cooking. In making soda bread, the acid in buttermilk reacts with the raising agent, sodium bicarbonate, to produce carbon dioxide which acts as the leavening agent. Buttermilk is also used in marination, especially of chicken and pork.

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