Vegetables of all types form a most valuable part of our diet. They play an important role in maintaining general good health, owing to the presence of mineral elements and vitamins. These substances help to build bone, teeth etc., Vegetables also protect the body from diseases and regulate the body processes on which vitality and good health depend. Presence of indigestible cellulose or roughage in vegetables helps to keep the large bowel functioning regularly in the elimination of unwanted matter from the body.

The green color of leafy vegetables is due to the presence of the green pigment chlorophy II. Chlorophy II is affected by pH. In acid conditions, it changes to olive green, and in alkali conditions, it becomes bright green. Some of the acids are released in steam when vegetables are cooking, particularly if they are cooked without a cover. The yellow or orange color of vegetables is due to the presence of carotenoids which are not affected by normal cooking processes or change in pH.

Root vegetables are of importance in the diet for the simple reason that they are filing, carbohydrate being their main food factor. Green vegetables are generally eaten in the form of vegetable stews and soups. In order to obtain the best possible nutrient, vegetables should be eaten raw as often as possible. Many of the valuable contents can be completely destroyed by bad cooking.

Values of Vegetables:

Vegetables can generally be defined as herbaceous plants used for culinary purposes. They are used to increase the quality of soups and also for their dietary potentials. They are made of chiefly of cellulose, hemi-cellulose and pectic substances. Sugar, starch, minerals and vitamins are also present in vegetables. In addition to vitamins and roughage, they also contain water and mineral salts, namely Calcium, Iron, Sulphur and Potash. Green vegetables provide very little else than roughage, water, Iron and Vitamin A, B and C vary in quantity with particular types of vegetables.

Fresh vegetables are of great importance in the diet because of the presence of vitamins and mineral salts. The cellulose incites peristaltic movement and indirectly helps digestion and prevents constipation. On the other hand, old and very coarse vegetables cause indigestion. Mature dry legumes including Cow peas in different varieties, Soya beans, Bambara nuts, Groundnuts and all other beans or dry peas are rich sources of protein and moderately rich sources of thiamine. Whereas, groundnuts are extra-ordinarily good sources of niacin.

Average composition of vegetables are as follows:
· Green vegetables: Water = 83% – 92%; Protein = 1% – 2%; Carbohydrates = 3% – 8%; Mineral salts = 1% – 2%; Vitamins = A, B, C, k.
· Root vegetables: Water = 75% – 85%; Protein = 0.5% – 2%; Carbohydrates = 5% – 18%; Mineral salts = 0.8% – 1%; Vitamins = A, B, C.
· Pulses: Water = 70% – 78%; Protein = 5% – 15%; Carbohydrates = 14% – 18%; Mineral salts = 0.5% – 1%; Vitamins = B.

Classification of Vegetables:

Vegetables may be divided into the following classes

1. Green – (leaves) cabbage, Spinach, Green beans.

2. Bulbous roots – Onions, Shallots, etc.

3. Roots or Tubers – Potatoes, Cassava, Yams, Carrots, Cocoyam, etc.

4. Flowers or Head – Broccoli, Canliflower, Okro, Pumpkin, ‘Isapa’, etc.

5. Fruits – Eggplant, Cottonseed, Cashew, Benniseed (Sesame), ‘Apon’, Breadfruit, Cucumber, ‘Ogbono’, Beans, Peas, Tomatoes, Red and green pepper, Corn, Groundnut, Soya beans, Bambara nut. (The bean and nuts are also referred to as Legumes and pulses.)

Choices of Vegetables:

Vegetables should be chosen carefully. The following points should be considered in order to get adequate nutritional benefits:

1. Choose fresh, crisp vegetables of good color. Damaged, wilted and bruised vegetables should be avoided as there is likely to be waste and loss of nutrients.

2. Root vegetables should be firm and free of spade marks.

3. Choose vegetables of medium size. They are more economical to cook and are generally of the best flavour. Very large vegetables are often coarse in texture and poor in flavour.

4. Insect or mould-infected vegetables should be avoided.

5. Use vegetables straight from the garden or allotment whenever possible.

In conclusion, out-of-date methods should be discarded and the newer and improved methods adopted if vegetables are to take their rightful place in the diet.

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