Medicinal lactose is generally extracted from milk whey after concentration, crystallization, refinement, recrystallization, and drying. After different final treatment processes, products with different particle sizes, compressibility, and fluidity can be obtained. So as to meet a variety of needs.

Lactose is a disaccharide in which D-glucose and D-galactose are combined with β-1,4 bonds. It is also called 1,4-galactoside glucose and is a reducing sugar.

When crystallized from an aqueous solution, it contains a molecule of crystal water. White crystal or crystalline powder, the sweetness is about 70% of that of sucrose, the specific gravity is 1.525 (20°C), and it loses crystal water at 120°C. The melting point of anhydrous is 201-202°C and is soluble in water. Slightly soluble in ethanol, soluble in ether and chloroform. There are reductive and dextrorotatory properties. It can be hydrolyzed into equal molecules of glucose and galactose.

The solubility of α-lactose and β-lactose in water also varies with temperature. When α-lactose is dissolved in water, it gradually becomes β-form. Because β-lactose is more soluble in water than α-lactose, the initial solubility of lactose is not stable, but gradually increases until the α-type and β-type balance. Most of the lactose in sweetened condensed milk is in a crystalline state. The size of the crystals directly affects the taste of the condensed milk, and the size of the crystals can be controlled according to the relationship between the solubility of lactose and the temperature.

The lactose crystals formed by the rapid drying of the lactose solution (such as spray drying) are amorphous, glassy lactose. Generally, the α-lactose and β-lactose in the lactose solution exist in a balanced state, and the amorphous glass lactose maintains the α/β ratio of the original lactose solution. The crystalline state of lactose in milk powder is amorphous lactose, which crystallizes into α-lactose when it absorbs 8% of water