Evaluation Of ?-amylase Inhibitor Activity Of Three Northeast Oil Beans At Different Growth Stages

?-amylase inhibitor(?-Amylase Inhibitor,?-AI)is a general term that can inhibit the absorption of sugar in the gastrointestinal tract.Its role is to inhibit or reduce the activity of salivary amylase and pancreatic amylase in intestinal mucosa,and prevent the hydrolysis and digestion of carbohydrates in food.Reduce blood sugar and fat content.?-AI with good activity was obtained from the seeds of legume,wheat,wild amaranth and other crops.At present,?-AI has been isolated from beans,wheat,wild amaranth and other plant seeds,among which the?-AI extracted from beans has the highest activity.Therefore,this topic chooses the pods of northeast soybean planted by the College of Modern Agriculture and Ecological Environment of Heilongjiang University,and selects three kinds of soybean pods with the highest inhibitory activity according to the previous research,namely Jinguan bean,Huiguan bean and Xiangguan bean.The changes and properties of?-AI activity were studied from the 10th,15th,20th,25th,30th,35th and 40th days after flowering of the three kinds of legumes,and the highest?-AI level period of the three kinds of beans was determined,providing an optimal selection growth period for the development of?-AI products in beans.In this study,three kinds of bean pods at different growth stages were sampled,and the crude?-AI were extracted according to the previous research in order to determin the inhibition rate.Then,according to the half inhibitory concentration,total activity and specific activity as evaluation indexes,the bean pod varieties at the growth stage with the highest inhibitory activity were screened.Next,evaluation of?-AI properties in vitro was estimated,including the effect of incubation time on the inhibition rate of?-AI,the effect of?-AI concentration on the inhibition rate,the thermal stability of?-AI,the acid-base stability of?-AI,the digestive stability of?-AI,the stability of?-AI for metal ions,and the stability of?-AI for food additives.The results are as follows:through the determination of the inhibition rate of three kinds of bean pods in different growth periods,it shows that the inhibition rate of three kinds of bean pods changes quite a little from 10 to 25 days after flowering,and the inhibition rate is only about 20%?40%.When the bean growth reaches 30 days,the inhibition rate increases significantly.When it grows to 35 days and 40 days,the inhibition rate changes are close to flat.At 40 days,the inhibition rate of Jinguan bean is(91.90±0.48)%,the inhibition rate of Huiguan bean is(88.45±0.38)%,and the inhibition rate of Xiangguan bean is(91.15±0.76)%.The IC₅₀value,total activity and specific activity of three kinds of beans in the 30th,35th and 40th days after flowering were compared.Huiguan bean has the highest inhibitory activity in the 40th day after flowering,with IC₅₀value of(2.60±0.06)mg/m L,total activity of 1271.23 U and specific activity of 0.38 U/mg protein.Then the properties in vitro of bean pods in the40th day after flowering were evaluated.The results showed that the inhibitory ability on porcine pancreatic?-amylase increased with the prolongation of incubation.The inhibition rate of?-AI was linearly correlated with the increase of its concentration,and the inhibition rate increased gradually in the range of 1.02?5.86 mg/m L.When the inhibitor concentration reached to 5.86 mg/m L,the inhibition rate was the highest(90.76±1.78)%.The inhibitor maintained high inhibitory activity in the temperature range of 30?80°C;the inhibitory activity stayed stable in the range of p H 3.0?9.0;in vitro simulated gastrointestinal assays(81.20±1.20)%inhibition rate of the inhibitor in bile could still be achieved after treatment in intestinal juice,although the inhibitor activity was slightly decreased,the inhibition rate was still at a high level(65.08±0.98)%.However,after the inhibitor was treated in gastric juice environment,the inhibition rate decreased to(8.42±2.26)%;the stability study of?-AI for metal ions showed that Na⁺,Fe³⁺,Ca²⁺and Mg²⁺could increase the inhibition rate of?-AI,and Ca²⁺had the strongest promotion effect.There was no significant difference in the inhibition rate of?-AI by adding a certain concentration of sucrose and citric acid,and there was little difference in the inhibition rate.It can be considered that as the representative of common bean used sweeteners and soureners commonly used in food industry,sucrose and citric acid showed no negative effect on?-AI activities.Therefore,the bean pods of Huiguan had the highest inhibitory activity in the 40th day after flowering,and the inhibition rate reached the highest level when the reaction time was 15 min by in vitro?-AI property test.When the inhibitor concentration reached 5.86 mg/m L,the inhibition rate of Huiguan was the highest;the inhibitory activity was the highest in the tolerant temperature range of 30?80°C;the inhibitory activity was high in the range of p H 3.0?9.0;in vitro simulated digestive tract treatments showed that the inhibitor maintained high activity in bile and intestinal fluid,and the inhibitory activity in gastric fluid was greatly dropped.Adding metal ions Na⁺,Fe³⁺,Ca²⁺and Mg²⁺could improve the activity of?-AI;common food additives sucrose and citric acid had no negative effect on the activity of?-AI.