Human Nutrition 3(3+0)

Lesson 12 : Carbohydrates

Classification

Carbohydrates are classified based on the number of saccharide unit as:

• Monosaccharides or simple sugars – glucose, fructose, galactose.
• Disaccharides or compound sugars – sucrose, maltose, lactose
• Poly saccharides or complex carbohydrates – starch, glycogen, dextin, cellulose, pectin

Table: Classification of carbohydrates

Class	Examples	Some food sources
Monosaccharides	Glucose (dextrose, grape, sugar, corn sugar, blood sugar) Fructose (levulose, fruit sugar) Galactose	Fruits, honey, vegetables, corn syrup Fruits, honey, vegetables, corn syrup Occurs only from the digestion of lactose
Disaccharides	Sucrose Maltose Lactose	Sugar cane, sugar beet maple sugar, small amounts in fruits and some vegetables Cereal malts and sprouted legumes, fermented doughs Milk
Polysaccharide’s	Starch Glycogen (animal starch) Dextrin Cellulose Pectin	Grains and grain products, legumes, potato and other root vegetables, green banana Liver and muscle of animals Partial breakdown of starch by heat or in digestion Bran of cereal grains, skins and fibre of fruits and vegetables Guava, apple, wood apple

Carbohydrates differ in sweetness based on composition and source and may be ranked in decreasing order of sweetness as fructose, sucrose, glucose, lactose, dextrin and starch. Raw fruits are bland in taste as they contain starch which is broken down into simple sugars during the ripening process with development of sweet taste. The relative sweetness of sugars is given in table.

Table: Comparative sweetness of sugars

Sugar	Sweetness value
Fructose Invert sugar Sucrose Glucose Galactose Maltose Lactose	173 130 100 74 32 32 16

1. Monosaccharides

2. Disaccharides

3. Polysaccharides