As a result of this property of pectins it is commonly used in the preparation of jams and jellies. (Dietary Reference Intakes, 2001). Dietary fiber which are not soluble in water, are classed as insoluble fiber. Water insoluble fibres are found in whole wheat, wheat bran, seeds, nuts and vegetables. On the other hand viscous plant fibres are soluble in water. Examples of soluble fibres include pectins, gums and mucilages. Soluble fibres are found in fruits, oat and barley, legumes and beans.
The human body does not have enzymes capable of breaking down cellulose, hemi-cellulose and pectins and so fiber is not digested in the body. However, in view of their ability to absorb water, these indigestible substances serve a useful purpose in helping with the elimination of intestinal wastes. They are responsible for stimulating the peristaltic (rhythmic) movements of the gastrointestinal tract by adding bulk to the intestinal contents. The insoluble fiber needs chewing and may improve mastication of food. Dietary fiber absorbs water, swells and thus increases surface area of the mass (Elkins, 1999). As a result of this property there is increased contact between the food mass and enzymes and hence digestion improves. Adequate amount of fiber in diet also give a feeling of fullness. The sponge like swollen mass of fiber ensures smooth elimination of faeces. Fiber reduces transit time and binds some minerals such as calcium, iron, zinc, etc. Soluble fiber binds bile acids and cholesterol and helps carry these out of the body. There is no recommended dietary allowance for fiber. However, nutritional researchers and dieticians suggest that fiber intake be increased to 25 grams or more per day.
There are several sources of dietary fiber. Whole grain cereals, whole wheat flour, fruits such as apples with their skin, bananas, pineapple, vegetables such as cabbage, greens are all good