Lactose

Lactose is the sugar found in the milk of humans, cows and other mammals. Chemically it is a disaccharide, with the formula C12H22O11, made of one D-galactose and one D-glucose unit joined by a beta-1,4 bond. It exists in alpha and beta forms, and the beta form is somewhat sweeter.

Human milk holds about 7.5% lactose and cow's milk about 4.5%. Commercially it is produced from whey, the by-product of cheese making. It is only about one-sixth as sweet as sucrose, so it is a gentle sweetener rather than a strong one. In foods it serves as a humectant and sweetener in products such as ice cream and baked goods, and it is also used in baby foods. It is very soluble in water, slightly soluble in ethyl alcohol, and a white, odorless solid.