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Published 2015
Simple gravity easily splits unhomogenized cow’s milk into two parts. A lactose-rich water-based solution (whey) holding suspended particles of a major milk protein called casein sinks to the bottom as “skim milk” in any container. A top layer containing the much less dense milk-fat globules along with a small amount of the basic solution rises to the top as “cream.” See cream. Both parts can be manipulated into other forms through means including the action of lactic acid bacteria and/or some enzymes, possibly combined with heat. See buttermilk; cheese, fresh; sour cream; and yogurt. Agitating cream (or whole milk, or yogurt) under the right conditions produces butter along with a wheylike solution, true buttermilk. Various Old World peoples had mastered these and other transformations in ancient (in fact, prehistoric) times. Bacterially cultured products flourished from the Balkans eastward; concentrates of boiled-down milk were beloved in India; and simple unripened cheeses were familiar from northeastern to northwestern Europe.