0.4% ~ 2.3% of leafy vegetables, 0.6% ~ 1.5% of root vegetables, 0.3% ~ 1.3% of onion and garlic, and 0.2% ~ 0.7% of melons.
0.4% ~ 0.5% of solanaceous fruits and 0.6% ~ 1.7% of fresh beans. Minerals in vegetables not only have the function of regulating human physiological function, but also are important components of various tissues of human body. Calcium, iron and potassium are basic substances in human physiology, which can neutralize acidic substances in the body and maintain acid-base balance in the body.
Vitamin vegetables contain a small amount of B vitamins, such as vitamin B 1 (thiamine), B2 (riboflavin), B5 (nicotinic acid) and so on. The content of vitamin C is particularly rich, which is the main source of vitamin C needed by human body. Most leafy vegetables, such as tomatoes and peppers, contain more vitamin C. The nature of vitamin C is extremely unstable, and it is easy to be oxidized and destroyed by high temperature. Green, yellow and orange vegetables are rich in carotene, which can be converted into vitamin A in the body, so they are also called vitamin A precursors.
Sugar in vegetables can be divided into sweet sugar, non-sweet starch and cellulose. The sugar content of vegetables is not high, especially carrots, pumpkins, melons and onions. Other foods, such as vegetables, cucumbers, soybeans, cabbages and radishes, contain only a small amount of sugar. Starch is abundant in potatoes, taro, yam, arrowhead and leguminous vegetables, but less in other vegetables.
Cellulose is the main component of vegetable cell wall, which is ubiquitous in vegetables, and its content is about 0.2% ~ 2.8%, especially in vegetable slices. The content of cellulose is one of the signs indicating the quality of vegetables. Vegetables with low cellulose content are crisp, tender and juicy with good quality; If the content is high, the meat is thick, the skin is thick and the muscle is thick, and the edible value is low.
Organic acid vegetables contain only a small amount of organic acids except tomatoes. Spinach, water bamboo and bamboo shoots contain more oxalic acid, which will affect the body's absorption of calcium. Before cooking, blanching should be carried out to remove excess oxalic acid.
Many vegetables have a special flavor because they contain volatile oil. The content of volatile oil in vegetables is not much, such as 0.005% ~ 0.009% in garlic and 0.037% ~ 0.055% in onion. Volatile oil is a substance that forms the special taste of vegetables, which can stimulate appetite and help digestion. The volatile oil of onion and ginger has the function of sterilization and deodorization, and it is a good condiment.
The color of vegetables is composed of pigments. Chlorophyll is a green pigment, which is produced by sunlight. Spinach and rape contain more chlorophyll. Chlorophyll is an unstable substance, insoluble in water and soluble in alcohol. Chlorophyll is easily destroyed by acid and becomes dark green or yellow green. Carrots, tomatoes, red peppers and other vegetables all have yellow, red and orange pigments. Other green vegetables also contain colors such as yellow, red and orange, because these vegetables are rich in carotene, lycopene and lutein.