VEGETABLES

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Vegetables are those plants which are consumed in relatively small quantities as a side dish or relish with staple food. Vegetables are classified according to the parts eaten as food. For example; Fruit Vegetables (such as tomatoes, eggplant, okra, pepper), Root Vegetables (such as carrots, potatoes, onions), Seed Vegetables (sweet corn, cowpeas), Floral Vegetables (Hibiscus sabdariffa, cauliflower) and Leafy Vegetables (Telfairia occidentalis, Amaranthus cruentus).
PRODUCTION OF VEGETABLES
Vegetable crops are established in the field by direct seeding or by use of vegetative propagules or transplant. Transplants are produced in containers of various sorts in green house, protected beds and open fields. Either containerized or field grown transplants can be used successfully. Generally, containerized transplants get off to a faster start but are more expensive.
Advantages of starting vegetables as transplants include: - Maximum number of plants can be obtained from costly seeds. – Problem of crusting can be avoided. – Depth of planting is more easily controlled et.c. Success in growing good transplants depends on the insect, weed and disease free medium, adequate heat and moisture for growing the plants and enough light to ensure stocky growth of the plant. Good quality transplants exhibit certain features. They include: - Healthy green appearances, - Medium sized, - Absence of Flowers as well as Insect Pests and Diseases. Transplanting is done either very early in the morning or late in the evening after which heavy watering should be done. Maintenance practices in Vegetable production include: Watering, Weeding, Mulching, Fertilizer application, Control of pests and diseases.
For most vegetables, Ammonium fertilizers are applied 3 weeks after transplanting. 3 weeks after 1st application phosphate fertilizers should be applied. During flowering, single super phosphate should be used.
Method of Harvesting vegetables varies depending on the vegetables as well as the time of harvest. Vegetables can be used for a number of purposes; some of which includes: - as a steamed vegetable in soups and stews. E.g. Amaranthus. – as a side dish. – The fibre from stems and mature pods of Okra are used in the manufacture of paper and cardboard.
FACTORS THAT INFLUENCE NUTRITIONAL QUALITY OF VEGETABLES
Soil fertility affects the quality of most vegetables. Generally, the proper soil fertility increases the size, yield and quality. Fertilizers tend to correct soil nutrient deficiencies that would otherwise reduce Vegetable quality, moisture stress induces fibre formation, resulting in tough root crops, celery stalks and leaf tissue of salad vegetables. Erratic irrigation can lead to tomato fruit rots, cracking in melons and cabbage heads, leaf burn in lettuce and regrowth of onion bulbs and potatoes. Harvest time influences quality, pesticides may influence quality and taste, storage and processing affects the nutritional value. Almost all Planting operations (Pre-, during and Post-) influences the nutritional quality of vegetables.
FOOD VALUES OF VEGETABLES
Vegetables play an important role in meeting the needs of humans for vitamins and minerals. Vegetables are an excellent source of vitamins and minerals. Vegetables have high water content: the energy content is usually low. Thus, vegetables have a relatively high content of nutrients permit of energy. Humans require about 2500 calories per day. For those with a low energy requirement, due to a limited physical activity, vegetables are essential to balance the diet and to prevent an overweight condition. Nutritional quality includes not only fat, protein, carbohydrates, calories and vitamins but also the ability of the product to maintain and improve human health. For example; the balance of individual amino acids within a protein is more important than the total amount of protein. Gelatin is mostly protein but contains amino acids which are not required to be ingested for human health. In other words, nutritional quality is a complex term that cannot be defined as the presence of a few chemical substances in a vegetable.
The carbohydrate content per fresh weight is generally low in most vegetables. Some vegetables contain sugar (starchyose and raffinose) which are not digested by humans. Instead, they reach the large intestines where they are fermented by anaerobic bacteria causing intestinal disturbance and flatulence. Much of the sugar from carbohydrates that is absorbed by the body is converted to fat which the muscles use as fuel for mechanical energy. The nervous system also uses considerable amount of energy to maintain itself in working order and 20% of the basal metabolism takes place in the brain. The nervous system appears to get its energy entirely from carbohydrates as it seems to have no important source of stored energy. It must depend entirely upon the carbohydrates supplied by the blood stream. Vegetables can provide these carbohydrates.
Vegetables are good sources of fibres. Various functions of fibres include: - lowering of blood cholesterol levels, - enhances the reabsorption of bile, - helps prevent constipation, - reduces the incidence of colon cancer, cardiovascular(heart) disease.
Proteins serve as the building blocks of living cells and are found in enzymes, many hormones, antibodies. The common components of proteins are AMINO ACIDS. Some amino acids can be produced by the human body; others cannot and are called ESSENTIAL AMINO ACIDS.
Vitamins are required for normal body functions and some may be provided in a precursor form. Fat- soluble vitamins are stored in the body but water-soluble vitamins are not and must be supplied daily. Vegetables supply major amounts of the fat soluble vitamin A and the water-soluble vitamin C, Thiamine, Riboflavin and Niacin. Carotene, a vitamin A precursor is orange in colour and is found in carrots, sweet potatoes, tomatoes and leafy vegetables. Carotene is very stable during the handling and storage of most vegetables. Vitamin A is essential for the maintenance of cells. It maintains resistance to infections, increases life, delays senility and is a necessary part of the reactions that occur in the eye for vision. Vitamin C is required daily by humans (about 60mg). Leafy vegetables, sweet potatoes and tomatoes are good sources of vitamin C. Vitamin C are essential for good teeth and bone formation and the healing of wounds. Some results suggest that vitamin C also helps to reduce stress, prevents cold and reduces skin disorders, Thiamine (vitamin B1) is essential for maintaining a good appetite and normal digestion. It is necessary for growth, fertility, lactation and normal functioning of the heart and nervous tissue. Many vegetables are good sources. __ Riboflavin (vitamin B2) is included in numerous functions in cellular metabolism. It is present in eye pigments that are involved in light adaptation. Many vegetables are poor sources but leafy vegetables, peas, beans are good sources. Niacin is involved in the biochemical machinery of the cells. It is not destroyed in ordinary cooking processes. Most vegetables are low in Niacin but meat, wheat and yeast are excellent sources.
Many minerals are important in body functions. The most important minerals found in vegetables are Calcium, Potassium, Phosphorus, Sulphur, Iron, Manganese, Magnesium and Zinc. About 750mg of calcium are recommended per day and this can easily be supplied by milk or cheese; however, many vegetables are excellent sources of calcium. Most diets contain adequate amounts of minerals. The increased use of vegetables in the diet will make the potassium-sodium levels about equal, which may help prevent high blood pressure. Vegetables and fruits supply about 25% of the required magnesium and about 20% of the required iron. The iron content of vegetables depends on the soil and other conditions under which the food was grown.
DID YOU KNOW: Vitamin C Increase Iron Absorption.