الفهرس 
VitaminsOnly 14 pages are availabe for public view
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Abstract
Vitamins are organic compounds occurring in natural foods especially in vegetables either as such or as utilizable “precursors”. Vitamins are needed for maintenance of skin, mucous membranes, bones, teeth and hair, vision and reproduction. They the help body to absorb calcium and phosphorous; needed for bone growth and maintenance. Vitamins are involved in blood clotting, normal functioning of nervous system and endocrine glands. They are also needed for metabolism of macro molecules.
Vegetables as a whole are considered as natural source of nutrients gifted by Almighty Allah to human beings e.g. carrot is a good source of vitamin A, needed for normal vision, like wise spinach and tomato contains enough amount of vitamin C to prevent and cure scurvy.
Food quality often deals only with the influences of primary production and industrial processing. Food preparation at home as final step of the chain has also great influence on quality determining parameters like sensory attributes and the content of vitamins and minerals. It can change them both in a positive and negative way.
Processing of food is often considered to cause losses of micronutrients. Nevertheless, it can also have positive effects. Several studies have shown an enhanced bioavailability of carotenoids from processed vegetables. Possible explanations for this result are the mechanical and thermal disruption of the cell matrix and the carotenoid-protein complexes.
Nutritional information is used increasingly by public agencies and agricultural industries to promote fresh produce. Consumers are looking for variety in their diets, and are aware of the health benefits of fresh fruits and vegetables. Of special interest are food sources rich in antioxidant vitamins (vitamins C, A, and E). The 2005 Dietary Guidelines recommended increasing the dietary intake of vitamins A, C, and E. Most of these nutrient requirements can be met by increasing the consumption of fruits and vegetables to 5–13 servings/day.
Consumption of fruits and vegetables is associated with reduced risk of cardiovascular disease, stroke, and cancers of the mouth, pharynx, esophagus, lungs, stomach, and colon.
This study was carried using eight different vegetables, tomato (solanum esculentus), okra (abelmoschus esculentus), zucchini (cucurbita pepo), beans phaseolis (phaseolis coccineu), green beans (pistum sativum), mulukhya (corchorus olitoris), spinach (spinacia oleracea) and artichoke (Cynara carduculus). These vegetables were utilized in the study at food analysis laboratory, Alexandria University, Egypt.
Vegetables were processed with different types of heat treatments by frying, roasting, boiling and microwaving. One of the aims of this study was carried out to determine the chemical composition of fresh and processed vegetables (boiled, fried, roasted, and microwaved), including (vitamin C, β carotene, total phenolic acid, total poly phenol, total antioxidant capacity, lycopene, and flavonoinds). On the other hand, this study aimed at assessing proximate analysis of fresh and processed vegetables (moisture, ash, protein, fat, and carbohydrate by difference) was carried out.
Our result can be summarized as follow:-
1- Fresh tomato contained the highest moisture content followed zucchini.
2- Mean moisture content of different vegetables increased with boiling and decreased with other heat treatment (frying, roasting, and microwaving)
3- Mean ash and protein significantly decreased with heat treatments, while carbohydrate significantly increased. Fat content was affected by heat treatment as it decreased except in fried samples where they contained the highest fat percentage.
4- Fresh samples contained the highest percentage of β carotene and vitamin C. as they decreased with heat treatment followed by microwaved samples then fried and roasted samples, boiled vegetables contained the lowest vitamin content. 5- Fresh tomato contained the highest β carotene content followed by green beans then zucchini. 6- Fresh mulukhya contained the highest total phenolic content and antioxidant activity. Phenolic acids decreased with heat treatment
7- Lycopene and total antioxidant activity significantly increased with thermal treatments.
8- Microwaved tomato had a higher lycopene content followed by fried and roasted tomato, while fresh tomato contained the lowest lycopene content.
9- Processed vegetables had a higher poly phenolic acid content than fresh vegetables as it significantly increased with heat treatment. 10- Fresh mulukhya contained the highest vitamin C content followed by spinach then tomato. Okra contained the lowest vitamin content.
11- Vitamin C decreased with heat treatment, microwaved vegetables contain the higher vitamin content than fried, roasted and microwaved vegetables It is therefore recommended to:
1- Increase consumption of vegetables which usually associated with reducing the risk of cancer.
2- Increase consumption of processed tomato (microwaved, fried, and roasted) usually associated with the high intake of lycopene and other antioxidants.
3- Microwaved vegetables contained higher vitamin A and C, and then fried and roasted samples, boiled vegetables contained lowest vitamin content