Buttermilk

Buttermilk is a dairy drink made by adding lactic acid bacteria to milk to produce a fermented drink; traditionally it was the nearly fat free milk left after churning butter from cream, cultured with natural bacteria before and during churning, which gave it a slightly sour taste and helped prevent spoilage. With the spread of refrigeration in industrialized countries, butter there is now typically made from uncultured, or sweet, cream, so most modern buttermilk is instead produced by inoculating fresh, pasteurized milk, and it is available at different levels of fat content. Buttermilk is drunk as a beverage and used in cooking; drinking it remains common in warmer climates where unrefrigerated milk sours quickly, since the fermentation helps prevent further spoilage, and in soda bread the acid in fermented buttermilk reacts with the baking soda leavening agent to produce carbon dioxide, while buttermilk is also used to marinate meat, especially chicken and pork.