Disaccharides or double sugars results when two hexoses are combined with the loss of one molecule of water. On hydrolysis they split into mono-saccharide units. Sucrose, maltose and lactose are the three important disaccharides contained in our food.
Sucrose is the white or brown sugar we use every day. This is produced from sugar cane and sugar beets. Many Fruits and vegetables also contains small amount of sources. Although cane sugar and beet sugar differ in colour and texture, they have the same caloric value. Molasses contain more than 50%sucrose.during digestion sucrose is hydrolised to glucose and fructose.
Maltose or malt sugar does not occur in the average diet. It occurs in sprouting grains, malted cereals and malted milk. Among sweetening agent this is found in corn syrup and corn sugar. In the body the most important source of maltose is as an intermediate product in the digestion of starch. When hydrolised, maltose yield two molecules of glucose.
Lactose or malt sugar is produced by minerals and is the only dietary carbohydrate of animal origin. Human milk contains 6.8%of lactose whereas cow’s milk contains 4.9% when lactose is hydrolised, galactose and glucose are formed.