From yogurt to buttermilk and Cheddar to ricotta cheeses, a key step in the manufacture of these very different dairy foods is lowering pH though the development or addition of acid.

Acid has many functions in dairy foods. "First, acids have a major role in protecting dairy foods against spoilage and growth of pathogenic organisms. This is especially true in yogurt, buttermilk, sour cream and other products at or below pH 4.6. They also play a role in products with higher pH, such as cheese," says Dave McCoy, principal scientist, Chr. Hansen Inc., Milwaukee, Wis.