Study On Preparation And Research Of Active Proteins And Polypeptides Of White Kidney Bean

White kidney bean, its biological name is kidney bean, also known as green beans, white beans, etc. In yunnan, guizhou, sichuan, gansu, shanxi, inner mongolia, heilongjiang, jilin and other provinces, the white kidney beans are all planted. The planting area of yunnan province is the largest, its average planting area is about 20000 hectares, and output is about 40000 tons every year. Per hundred grams white kidney beans content 1520 mg potassium and 0.8 mg sodium, so it is a kind of high potassium and low sodium foods, very suitable for patients with heart disease, arteriosclerosis and salt-avoid consumption. The protein content of white kidney bean is 19.29%, similar to the red kidney bean, mung bean, adzuki bean and broad bean. The essential amino acid composition of white kidney bean protein is close to FAO/WHO standard pattern, it is a kind of high quality protein resources with high nutritional value and easy to digest. In recent years, the plant lectins and a-amylase inhibitor of white kidney bean were researched more, followed by the extraction and nutritional value analysis of white kidney bean starch, dietary fiber, polysaccharide and isolated protein. Reports about the preparation of white kidney bean polypeptides with the function of auxiliary lipid-lowering and weight-reducing are haven’t seen. In this study, the white kidney bean was the raw material, and the preparation of white kidney bean protein and auxiliary lipid-lowering and weight-reducing functional polypeptides were researched, which was intend to provide new ways for the development of health foods. The research contents of this paper are as follows:1. Study on the extraction technology and molecular composition of white kidney bean albumin. Used albumin extraction ratio as the index, by single-factor and orthogonal experiments to determine the optimum process conditions of albumin extraction, the conditions were as follows:solid-liquid ratio 1:8(g/mL), extraction temperature 55℃ and extraction time 3h, and the ratio of albumin extraction was 48.15% under the above conditions. The isoelectric point of albumin is 3.5. SDS-PAGE electrophoretic analysis of albumin showed that there are 5 protein subunit bands, their molecular weights were 66.71、 52.90、35.31、30.52 and 21.12ku respectively.2. Preparation and stability study of white kidney bean active polypeptides. The a-AI extract was prepared by ultrafiltring the white kidney bean albumin extract two times. Used a-AI extract as raw material, polypeptide yield and a-amylase inhibitory activity as the index to determine 3.350 acid protease as the optimum enzyme to prepare active polypeptides. Through single-factor and orthogonal experiments, the optimal process conditions of preparing white kidney bean active polypeptides were determined as follows: enzyme dosage 3200 U/g, temperature 55℃, pH2.2 and time 60min. And the a-amylase inhibitory activity of polypeptides was 80.82% under the above conditions. The contrast analysis showed that active polypeptides had a better stability than a-AI extract at different pH. And white kidney bean active polypeptides had higher thermal stability than a-AI extract, and the a-amylase inhibitory activity of polypeptides could keep for a longer time under 85 and 90℃. Electrophoretic analysis showed that the molecular weight of a-AI extract were 34.98 and 29.70ku, and the molecular weight of white kidney bean polypeptides was 7.53-9.09ku.3. Research of auxiliary lipid-lowering and weight-reducing function of white kidney bean active polypeptides. By animal experiments, auxiliary lipid-lowering and weight-reducing function of white kidney bean active polypeptides on the mice were researched. Animal experiments results showed that white kidney bean active polypeptides could significantly reduce the serum triglyceride (TG), total cholesterol (CHO), and elevate high-density lipoprotein cholesterol (HDL-C), and could significantly reduce the body weight, weight gain and lipid/body weight ratio of mice, so white kidney bean active polypeptides had a good auxiliary lipid-lowering and weight-reducing effect, and the greater the dose, the better the results, there was a certain dose-response relationship. The research results had declared invention patent.4. Extraction and amino acid composition analysis of white kidney bean globulin. After extracting white kidney bean albumin, the rest pulp was used as raw material, the NaCl solution was used to extract globulin. Through single-factor and orthogonal experiments the optimum extraction technology of globulin was determined as follows: the concentration of NaCl 2.5g/100mL, solid-liquid ratio 1:22, temperature 55℃ and time 4.5h, the extraction yield of globulin was 41.46%. Electrophoresis analysis showed that globulin contented six protein bands. Amino acid composition analysis showed that the essential amino acid score of globulin was 84, globulin was a kind of high quality plant protein resources.