Beans include soybeans, peas, broad beans, cowpeas, mung beans, adzuki beans, cowpeas and so on. According to the nutrient content of beans, beans can be divided into two categories. One is soybean (which is divided into soybean, black bean and green bean, etc.), which contains high protein (35%-400%) and fat (15%-20%) and relatively little carbohydrate (20%-30%). The other is beans other than soybeans, which contain high carbohydrate (55%-65%), moderate protein (20%-30%) and a small amount of fat (less than 5%). The amino acid composition of protein of all beans is good, among which soybean is the best, its amino acid composition is close to the needs of human body, and it is rich in lysine which is relatively lacking in cereals.

Nutritional components of legume food

Compared with cereals, the seeds of beans contain much higher protein and fat. Soybean is the only plant food with high protein, high fat and high heat energy comparable to animal food.

Nutritional characteristics of legume food

Compared with other foods, leguminous foods such as soybeans have the following characteristics in nutrition:

(1) protein content is high.

Soybean is the reproductive organ of plants, and it accumulates a lot of polymer nutrients during its growth. Therefore, it contains a lot of protein, and the protein content of soybean is generally around 40%, and even as high as 52% in some varieties. Compared with meat food, the amount of protein contained in 1 kg of soybean (calculated by 40% content) is equivalent to the protein contained in 2.3 kg of lean pork or 2 kg of beef. This characteristic of soybean nutrition makes it of great significance in dietary structure.

(2) The nutritional value of protein is high.

The nutritional value of protein depends on the degree to which the amino acid composition meets the needs of human body. The composition of eight essential amino acids in soybean protein meets the needs of human body, so it is an excellent plant protein. In particular, it is rich in lysine, and its content is 10 times higher than that of cereal. The threonine content is about 5 times higher than that of cereals. Lysine is the first limiting amino acid in all cereals, so if soybean products are mixed with other cereals, it can not only make up for the lack of protein content in cereals, but also make up for the amino acids that other cereals lack, so that the nutritional value of mixed food protein has been significantly improved.

If15% soybean flour is added to wheat flour, the utilization rate of wheat flour protein will be increased by1.8 times, so soybean is an ideal complementary food for cereals. Other legumes, such as mung beans, adzuki beans, peas, broad beans, etc., have higher protein content than cereals, and are also rich in lysine, so they are also good complementary foods of cereals.

(3) The content of inorganic salts and vitamins is rich.

Soybeans and other beans are also rich in inorganic salts such as calcium, phosphorus, iron and zinc, and the content of B vitamins is significantly higher than that of cereals such as rice, flour and corn flour. Some are several times or even dozens of times higher. The content of thiamine in pea ranks first among all kinds of grain. Although soybeans and other beans do not contain vitamin G, the content of vitamin C in bean sprouts made of soybeans or mung beans can reach 20 mg/100 g if they are produced properly. Therefore, bean sprouts are still a good source of vitamin C. Therefore, regular consumption of bean products can supplement the essential elements of salt and vitamins, promote metabolism, stimulate appetite and improve health.

(4) Low carbohydrate content

Compared with cereal, the carbohydrate content of soybean is much lower, only 25% ~ 30%, and about half of it is raffinose and stachyose which cannot be digested and absorbed by human body, so bean products are excellent foods for diabetic patients. The carbohydrate content of other beans is much higher than that of soybeans, which is 50%-60%, and adzuki beans are higher. Using adzuki beans and rice (or millet) to cook rice and porridge will not only make the nutrition of rice or porridge more comprehensive, but also increase the fragrance of adzuki beans and stimulate people's appetite. Adzuki bean is silty after cooking, which is very suitable for making bean paste. Can be used to process all kinds of cakes and foods.

Soybean is also rich in soybean lecithin, aspartic acid, glutamic acid, choline and stigmasterol, which are beneficial to human health, promoting growth and development, enhancing memory, maintaining normal liver function, preventing arteriosclerosis and maintaining vigorous youthful vitality. The Secret Records of Yan Nian, a medical book in the Song Dynasty in China, holds that "taking soybeans can make people grow skin, benefit color, fill bone marrow, strengthen strength and replenish deficiency". At present, many countries in the world regard soybean products as healthy food or beauty food.