White, odorless, slightly sweet-tasting powder.
Lactose is a disaccharide, two simple sugars in one molecule. In this case, the sugars are galactose and glucose.
Lactose is mainly used as a fermentation substrate for lactic acid bacteria in dairy products such as yogurt and cheese. These bacteria break down lactose into lactic acid, which solidifies the milk, and creates an acid environment that favors the benign lactic acid bacteria over those that are more harmful.