The main nutritional characteristics of white kidney beans are similar to those of green beans and peas - they are high in protein (mostly more than 20%), fairly rich in starch, dietary fiber and minerals, and, more importantly, low in fat. These characteristics give it a high performance for healthy eating. The following data illustrate the main nutritional functional components of white kidney beans:

(i) Glycoproteins

(1) α-amylase inhibitor (α-AI), this ingredient is an important reason for the unique food and medicine value of the white kidney bean, there are two or three subtypes of α-AI reported so far, these inhibitors do not have significant inhibitory effect on the more vigorous α-amylase, and the starch concentration has almost no effect on the inhibitory effect of α-AI. α-AI can be widely used to inhibit α-Amylase hydrolysis of the starch in daily diet. The inhibitory effect of α-AI on α-amylase is mainly affected by its own protein concentration, temperature, acidity and alkalinity, metal ions and other factors. When the protein concentration of α-AI is less than 6.00 mg/mL, the inhibition of α-amylase by α-AI is dose-dependent. When the temperature was greater than 70 ℃, the inhibition rate decreased significantly with the increase of temperature, and when the temperature reached 90 ℃, the inhibition rate almost decreased to zero. Among the effects of acidity and alkalinity, α-AI had the highest activity at pH 6.9, and either acid or alkali treatment caused a rapid decrease in its inhibitory activity, which then stabilized, and the loss of α-AI's viability decreased with the extension of time. Among the metal ions, sodium, potassium, calcium and magnesium ions had activating effects on α-AI within a certain concentration range, among which potassium ions had the most significant activating effect; while ferrous ions, carbon dioxide, zinc ions, manganese ions and copper ions had strong inhibitory effects on α-AI.

(2) Phytohemagglutinin (PHA) is also a component of white kidney bean, which has agglutination effect on blood cells, lymphocytes and sperm cells, and belongs to a kind of antinutritional factor, and the degree of this kind of agglutination effect of phytohemagglutinin has nothing to do with blood type. The anti-nutritional effect of phytoagglutinin is reflected in its agglutination of blood cells, which will lead to the destruction of the normal structure of the small intestine, thus reducing the utilization rate of nutrient absorption and pathological diarrhea, and will also lead to the inhibition of intestinal cell growth and differentiation. Phytoagglutinins enter the circulatory system and damage the normal structure of the pancreas, causing systemic reactions. Ingestion of undercooked white kidney beans produces erythrocyte agglutination, varying degrees of hemolysis, and may lead to inflammatory reactions [7]. Therefore it is known that qualified white kidney bean extract products dealing with plant lectins are very important.

Bioactivities of White Kidney Bean

White beans

Antioxidant activity of white kidney bean: the antioxidant effect of white kidney bean is mainly to inhibit lipid peroxidation, it was found that white kidney bean extract can significantly reduce the level of protein carbonylation in the plasma of the organism after a high-fat diet, and has a similar effect on cardiac tissue. White kidney bean extract can also reduce the hyperglycemic state of catalase and superoxide dismutase activity and lipid peroxidation-induced tissue damage, which can increase the total antioxidant activity of the diabetic organism, and reduce collagen levels, reduce the incidence of cardiac complications.

White kidney bean hypoglycemic function: the hypoglycemic effect of white kidney bean is reflected in its ability to reduce the damaging effects of type II diabetes on the pancreas, kidneys and liver. In healthy people, taking 6 g of white kidney bean extract 15 min before a meal can effectively reduce the glycemic response after eating white rice. Studies have shown that adding white kidney bean α-amylase blocker at 30% to convenient porridges (rice porridge, oatmeal porridge, barley porridge, and lotus seed porridge) reduced the GI values to less than 55. The addition of white kidney bean extract in the second stage also effectively reduced the GI values after human intake. A study conducted by the State Key Laboratory of the School of Food Science at Jiangnan University on the effects of α-amylase inhibitors on the physiological metabolism and intestinal flora of patients with type II diabetes mellitus showed that white kidney bean extract prolonged the digestion time of starch in the intestinal tract by decreasing the absorption of starch in the digestive system, so that more starch could reach the large intestine. By changing the structure of intestinal flora, it can help blood sugar control, reduce glycated hemoglobin (HbA1c), fasting blood sugar and postprandial blood sugar.

Taking white kidney bean extract may also have the effect of reducing weight and fat. There are many products on the market containing white kidney bean extract for weight loss, these white kidney bean extract is a kind of α-amylase inhibitor, because this kind of substance can inhibit the activity of amylase, so that the human oral cavity, the pancreas in the amylase activity decreases, respectively, play a role in inhibiting salivary amylase and pancreatic amylase. In the human digestive system, amylase facilitates the digestion of starch, converts starch into glucose for absorption, and finally generates calories. The α-amylase inhibitor in white kidney bean extract inhibits the activity of amylase, so part of the starch cannot be digested and absorbed, and no calories are produced. Therefore, these α-amylase inhibitors in white kidney bean protein are also known as "starch blockers".