Classification of Carbohydrates

Carbohydrates are classified into mono, di, oligo and polysaccharides. There are six naturally occurring carbohydrates of interest in foods -glucose, fructose (monosaccharides- are simplest form of carbohydrate and can not be hydrolyzed further.); sucrose, maltose and lactose (disaccharides) and starch (polysaccharide). Simple carbohydrates (sugars) are crystalline solids and water-soluble.
• Glucose (also called Dextrose /grape sugar/ corn sugar) is the simplest monosaccharide and is widely available in nature. It is the major energy fuel for the human body.
• Fructose (also known as Levulose / fruit sugar) is about twice sweeter than sucrose. It is used as sweetener by diabetics or obese people. It is also observed that fructose does not require insulin hormone for utilization.
• Maltose (Malt sugar) – is an intermediate product of starch digestion. It is also present in malted and fermented grains. Maltose (malt sugar) on hydrolysis yields two glucose units.
• Sucrose on hydrolysis yields equal parts of glucose and fructose.
• Lactose (milk sugar) provides equal quantities of glucose and galactose on hydrolysis.
• Polysaccharides (starch, glycogen) provide a number of monosaccharide units on hydrolysis. But the uncooked starch in food is not easy to digest, as the digestive juices can’t penetrate the cell wall of plant, which contains the starch. Gelatinization of starch (powdered form) occurs when it is mixed with water and heated to 850 C, and this on cooling leaves a semisolid gel.
Glycogen is the reserve carbohydrate in man and animals present in liver and muscles and is synthesized from glucose.
Pectin found in soft fruits and in plant cell walls is a mixture of polysaccharides. Cellulose on hydrolysis by acids yields high number of ß-D glucose.