Lactose is the primary ingredient in the milk of all mammals. Lactose is not sweet to taste. Lactose consists of one galactose carbohydrate and one glucose carbohydrate.
These are bound together by a β-1-4 glycosidic bond. Lactose is a reducing sugar since it has one free hemiacetal hydroxide.
Maltose has two glucose monosaccharide molecules bound together. The link is α-1- 4 between the first carbon atom of glucose and the fourth carbon of another glucose molecule. On hydrolysis by acid or maltase enzyme, one mole of maltose gives two moles of D-glucose. Maltose has a free hemiacetal hydroxide, hence it undergoes mutarotation. It exists as both α-Maltose and also β-Maltose. It gives a positive test with Benedict’s and Tollen’s reagent.