DISACCHARIDES

Disaccharides are two monosaccharide sugar molecules that are chemically joined by a glycosidic linkage (- O -) to form a “double sugar” (the prefix “di” means
two). When two monosaccharide molecules react to form a glycosidic bond (linkage), a water molecule is generated in the process through a chemical reaction known as condensation. Therefore, condensation is a reaction where water is removed and a polymer is formed. The most well known disaccharide found in nature is sucrose, which is also called cane sugar, beet sugar, or table sugar.Sucrose is a disaccharide of glucose and fructose. Lactose or milk sugar is a disaccharide of glucose and galactose and is found in milk. Maltose is a disaccharide composed of two glucose units. Disaccharides can easily be hydrolyzed (the reverse of condensation) to become monosaccharides, especially in the presence of enzymes (such as the digestive enzymes in our intestines) or alkaline catalysts. Invert sugar is created from the hydrolysis of sucrose into glucose and fructose. Bees use enzymes to create invert sugar to make honey. Taffy and other invert sugar type candies are made from sucrose using heat and alkaline baking soda. Disaccharides are classified as oligosaccharides (the prefix “oligo” means few or
little). This group includes carbohydrates with 2 to 20 saccharide units joined together. Carbohydrates containing more than 20 units are classified as polysaccharides.