Disaccharide

A disaccharide is a sugar (a carbohydrate) composed of two monosaccharides, such as glucose and fructose that make up the disaccharide sucrose. It is formed when two sugars are joined together and a molecule of water is removed. Due to this, disaccharides cannot hydrolyse, meaning their molecules are unable to be broken down through a reaction with water. For example, milk sugar (lactose) is made from glucose and galactose whereas cane sugar (sucrose) is made from glucose and fructose.

Sucrose, a common disaccharide

Common disaccharides

Disaccharide	Unit 1	Unit 2	Bond	Notes
Sucrose (table sugar, cane sugar, saccharose, or beet sugar)	glucose	fructose	α(1→2)	Sucrose is found naturally in many food plants.
Lactose (milk sugar)	galactose	glucose	β(1→4)	Lactose is found in milk products.
Maltose	glucose	glucose	α(1→4)	Produced during the malting of barley
Trehalose	glucose	glucose	α(1→1)α	Present in fungi and insects. Successfully produced at an industrial scale by enzymatic treatment of starch for use as a food ingredient.
Cellobiose	glucose	glucose	β(1→4)	-

Maltose and cellobiose are hydrolysis products of the polysaccharides, starch and cellulose, respectively. Some common Disaccharides are: Maltose, Lactose and Sucrose.