Disaccharides are too large to move through cell membranes, so they must be digested via hydrolysis. Disaccharides found in food include sucrose, lactose, and maltose, a grain sugar, all of these contain glucose.
Lactose is a naturally occurring carbohydrate found in the milk of most mammals. The disaccharide lactose occurs in milk, mainly free with a small extent as a component of higher oligosaccharides. Its concentration in milk varies with the mammalian source from 2.0% to 8.5%. Cow and goat milks contain 4.5–4.8% and human milk about 7%. It is the primary carbohydrate for developing mammals.
Lactose production in nature is limited to the mammalian breast, which contains the enzyme system (lactose synthase) necessary to create this linkage.
Lactose is a disaccharide consisting of galactose and glucose, linked by a β -L-4 glycosidic bond. In milk, lactose is normally found as either α-lactose or β -lactose or amorphous glass form (mixture of α- and β -forms).
Lactose is one of the lowest ranking in terms of sweetness, being about one-sixth as sweet as sucrose.
Sugar milk: Lactose
