Sugars - Definition, Types, Examples

Sugar is a food widely used as a sweetener. People sprinkle sugar on such foods as grapefruit and cereal to improve their taste. All green plants produce sugar. But most sugar that people use comes from sugar cane and sugar beets, which produce a sugar called sucrose. Other sources of sugar include cornstarch, milk, maple syrup and honey. Sugars are also referred to as simple carbohydrates because they are in their most basic form. Monosaccharides, disaccharides and polysaccharides are three types.

1. Monosaccharides

Monosaccharides are also called as simple sugars. Examples of monosaccharides include glucose, fructose, and galactose.

i. Glucose

Glucose is a type of sugar. Glucose is a product of photosynthesis. Honey and fruits like grapes and figs contain a lot of glucose. Pure glucose is a white crystal. It is about three fourths as sweet as sucrose. Its chemical formula is C6H12O6. Glucose belongs to a class of foods called carbohydrates. It is the most numerous of the monosaccharides, or simplest carbohydrates. Because of its simple chemical structure, glucose can be absorbed directly into the blood from the intestine. Most complex carbohydrates, including sucrose and starch, must be broken down into monosaccharides before being absorbed into the blood. Glucose is made commercially from starch.

ii. Fructose

Fructose is the sweetest natural sugar. It is a sugar produced by nearly all fruits and by many vegetables. Fructose also known as fruit sugar is nearly twice as sweet as sucrose. Fructose is used to sweeten such food products as diet foods, gelatin desserts, jams, jellies, soft drinks and syrups. It is the chief sweetener in honey. Foods that contain fructose taste as sweet as similar foods made with sucrose, but they may have fewer calories, fructose gives ice cream and sweets a smooth texture. It also absorbs moisture readily and so helps to keep baked goods from becoming stable. Fructose is produced commercially as a liquid, powder or tablet. Food processors use fructose primarily in the form of syrup prepared from maize.

iii. Galactose

Galactose is a simple sugar that is as sweet as glucose, and about 65% as sweet as sucrose. It is usually found in nature combined with other sugars.

2. Disaccharides

Disaccharides are also called as double sugars. Examples of disaccharides include Sucrose (Table Sugar), Lactose and Maltose.

i. Sucrose (Table Sugar)

Sucrose, generally known as cane sugar, is the primary carbohydrate produced during photosynthesis. It is carried into plants' storage organs.

ii. Lactose

Lactose is most generally referred to as milk sugar. Lactose of milk is the most important carbohydrate in the nutrition of young mammals.

iii. Maltose

Maltose is the chemical term for malt sugar. The formation of maltose is the first step in the digestion of starchy foods. The enzyme ptyalin in saliva changes starch into maltose. Other enzymes split the maltose into glucose. Commercially, the enzyme diastase in malt changes starch into maltose. Fermentation changes maltose into alcohol. This is recovered by distillation. Maltose is used for sweetening some foods.

3. Polysaccharides

Longer chains of monosaccharides and disaccharides are not regarded as sugars and are called polysaccharides. Polysaccharides are also called as complex carbohydrates, which are chains of glucose molecules. Examples of polysaccharides include starch and glycogen.

i. Starch

Glucose is a basic sugar that plants use to make starch. The most important food source for higher animals is a polysaccharide reserve found in plants. Grains and tubers both contain starch..

ii. Glycogen

Glycogen is a tasteless, odourless white powder. Glycogen is a carbohydrate. It is made up of basic sugar units called glucose that are linked together in branching chains. Glycogen is produced and stored in the liver and muscles. It is composed of excess starch and sugars in the body. These are first converted to glucose. Excess glucose is then changed into glycogen. Glycogen is often called animal starch. It is a reserve food and is easily reconverted to glucose.