Lactose is the principal carbohydrate in the milks of all mammals; non mammalian sources are very rare. Milk contains only trace amounts of other sugars, including glucose(50 mg\), fructose, glucosamine, galac- tosamine, neuraminic acid and neutral and acidic oligosaccharides The concentration of lactose in milk varies widely between species(Table 2.1). The lactose content of cows'milk varies with the breed of cow