Butter is a soft solid dairy product made by churning milk or cream, containing fat, protein, and water. Made is some countries from the milk of goats, sheep, or yaks, it is made in the West mostly from cows' milk only. Continuous mechanized production has been general since the 1940s. After skimming, the cream is ripened with a bacterial culture, pasteurized (see pasteurization), cooled to 4°C, and then churned, causing the butterfat to separate from the liquid residue, buttermilk. The butter is then washed, worked, colored, and salted.