Lactose is a disaccharide sugar composed of one galactose and one glucose unit linked by a β-1,4-glycosidic bond. It is the primary carbohydrate found in mammalian milk, typically comprising 2-8% of milk by weight depending on species. In food applications, lactose contributes mild sweetness, browning via Maillard reactions during heating, and texture in dairy products such as cheese, yogurt, and powdered milk. It exists in α and β anomeric forms, with the β-anomer being more soluble. Lactose is hydrolyzed by intestinal lactase into glucose and galactose for absorption. Industrially, it serves as a pharmaceutical excipient and in fermentation processes. Chemically stable under normal conditions but decomposes at high temperatures without boiling.