| There are abundant kidney bean resources in China.Kidney beans contain ?-amylase inhibitors(?-AI),which can inhibit the activity of mammalian and insect ?-amylase.In human body,?-AI can hinder the hydrolysis and digestion of carbohydrates then reduce the blood sugar levels,it is a natural substance for preventing and controlling diabetes and obesity.The extraction process of pure kidney bean ?-AI is complicated,with long cycle and high cost.Kidney bean ?-AI crude extract is simple to extract and has a strong inhibitory effect on?-amylase,but it contains Phytohaemagglutinins(PHA),which are harmful to the human body,cannot be directly applied to the food industry.Traditional methods will result partial or even complete loss of ?-AI activity while removing the activity of PHA.This paper was to explore a new method of removing the activity of PHA while retaining the activity of ?-AI in the crude extract and optimized the process.The ?-AI crude extract which was obtained by the new way was researched.At the same time,for the comprehensive utilization of resources,the extracted residue is applied to rice noodles to obtain a nutrient-fortified rice noodle.Firstly,the activity of ?-AI and PHA in five kinds of kidney beans from Inner Mongolia was compared,and the effect of dehulling on the activity of ?-AI and PHA and antioxidant capacity was also studied.The results showed that the whole grains of flower kidney bean had a higher inhibitory rate on ?-amylase and the high content of total phenol and total flavonoid content,with 1.00 mg GAE/g and 0.86 mg CE/g respectively.It also had strong antioxidant capacity.After comprehensive considerations,flower kidney bean is the best raw material for the preparation of ?-AI crude extract.Secondly,taking ?-AI and PHA activity of kidney bean extract as indicators,the optimized extraction bean meal,material-liquid ratio,p H,time and temperature was 60 mesh,1:5,p H 6.4,120 min and room temperature,respectively.At the same time,the effects of different proteases on the activity of ?-AI and PHA in the water extract were compared.The result showed that the acid protease was the best one to remove the lectin activity from kidney bean extract among the proteases used in this research.The process was optimized as following: enzyme dosage of 1000 U/g,p H 2.5 and 90 min hydrolysis at 70?.In this condition,the lectin activity of the kidney bean extract was completely eliminated,and the inhibitory activity of ?-amylase remained 75.38%.Thirdly,the properties of the obtained kidney bean ?-AI extract with no PHA activity were studied.The results showed that the ?-AI crude extract had high stability in the p H range of 2-10 and the temperature that below 60?.When the temperature rises as high as 80?,the?-AI crude extract inhibition rate retention rate is 74.85%.,The ?-AI crude extract loses its inhibitory activity when the temperature rises to 90?.With the increase of incubation time,the inhibition rate of ?-AI crude extract showed a trend of first increasing and then stable,and the inhibition rate reached the highest at 10 min.The ?-AI crude extract has the inhibition rate on different types and concentrations of starch hydrolysis.The ?-amylase inhibitory of extract remained 87.37% after simulated gastric environment and intestinal environment while the free radical scavenging capacity and FRAP value of DPPH,ABTS decreased from 10.18?mol TE/g,28.36 ?mol TE/g,72.22 ?mol Fe(II)/g to 6.51 ?mol TE/g,23.06 ?mol TE/g and63.10 ?mol Fe(II)/g,respectively.After being added the kidney bean ?-amylase inhibitor at the level of 3% in staole food,the degree of hydrolysis of starch in bread,rice,steamed bread and corn steamed bread was reduced from 77.79%,84.58%,84.91%,and 77.90% to 30.48%,40.98%,19.08%,and 15.12%,respectively and the e GI of bread,rice,steamed bread and corn steamed bread was reduce from 65.00,71.65,68.17 and 63.41 to 30.69,39.51,22.30 and19.69,respectively.Finally,the residue was added to rice noodles to prepare a residue-enhanced rice noodle and the quality characteristics of rice noodles with different residue addition levels were discussed.The results showed that with the increase of residue addition,the nutritional properties and antioxidant capacity of rice noodles were increased,but the quality characteristics were decreased.Considering comprehensively,selecting 10% addition amount to prepare the residue-enhanced rice noodles.The content of protein and total phenol of residue-enhanced rice noodle were increased by 1.18 and 2.71 times than control.The antioxidant capacity of residue-enhanced rice noodle was significantly increased(p<0.05).At the same time,the quality decline is not obvious and is in an acceptable range.Sensory evaluation showed that there was no significant difference between rice noodles added with5% and 10% residue and control(p>0.05). |
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