Study On The Biochemical Dynamics And In Vitro Digestion Characteristics Of Black Bean Tempeh During Fermentation

In order to enrich the variety of tempeh and improve the utilization rate of black bean food,the black soybean was used as raw material and Rhizopus oligosporus was used as fermentation strain in this experiment.Firstly,single factor experiment and response surface methodology were used to optimize the fermentation process of black bean tempeh,and the basic nutritional components and aroma components of the product were analyzed.secondly,the basic physical and chemical indexes,protein degradation,phenolics content,ACE(angiotensin converting enzyme)inhibitory activity and antioxidant activity of black soybean during fermentation were revealed.Finally,in vitro simulated digestion model was used to explore the effects of fermentation on protein degradation,phenolics release,ACE inhibitory activity and antioxidant activity in the digestion process of black soybean.The results were as follows:1.Analysis of fermentation technology,nutrition and flavor of black bean tempeh.The optimal fermentation process of black bean tempeh was as follows: the fermentation time was 39 h,the fermentation temperature was 35 ?,inoculation amount was 0.26% and lactic acid addition amount was 1.50%.Under the condition,the sensory score was 93.90,and tempeh had the highest sensory quality than the others.The results of basic nutrition composition and aroma were showed as follows: there was no significant difference(p>0.05)in ash content and crude fat content before and after fermentation,the moisture content and crude protein content were significantly increase(p<0.05)than those of the samples without fermentation.A total of 24 kinds of aroma components were detected in fermented black bean tempeh,14 kinds substances and three kinds of aldehyde,hydrocarbon and ester components were found than those of the unfermented sample.2.Changes of biochemical dynamics,antioxidative and ACE inhibitory activities in the fermentation of black bean tempeh.During fermentation,ergosterol content fluctuated with the peak of 911.39 ?g/g within 33 h,the reducing sugar content increased to the highest value of21.18 mg/g during the first 27 h and then decreased until the end of fermentation,the content of amino acid nitrogen showed a gradual increase to the highest level of 0.87 g/100 g as the fermentation progressed,the content of soluble protein decreased to the lowest level of 32.48mg/g within 15 hours and then increased until the end of fermentation,the content of peptides below 10 kDa and degree of protein hydrolysis increased significantly(p<0.05),with the maximum values of 335.60 mg/g and 29.43% respectively,meanwhile,qualitative analysis of SDS-PAGE(sodium dodecyl sulfate-polyacrylamide gel electrophoresi)showed that the band density of fermented black soybean in 25-35 kD and<25 kDa regions gradually increased,and the peptide map analysis further showed that fermentation increased the content and types of small and medium molecular weight proteins in black bean tempeh.ACE inhibitory activity decreased rapidly and reached the lowest level of 61.72% at 39 h after fermentation.In addition,the contents of total phenol,total flavonoids and proanthocyanidins were 2.23 mg/g,0.70 mg/g and 2.22 mg/g respectively,which were significantly higher than the contents of unfermented samples(p<0.05),and the contents of total phenol,total flavonoids and proanthocyanidins were significantly positively correlated with antioxidant activity(p<0.05).The above results not only showed that the fermented black soybean protein was obviously degraded,the content and types of small molecular peptides increased significantly(p<0.05).They also showed that fermentation can improve the antioxidant activity of black bean tempeh.3.Digestion characteristics of black bean tempeh in vitro.In the process of simulated digestion in vitro,soluble protein content was significantly higher than that of unfermented black soybean in other treatment stages except intestinal treatment(p<0.05).SDS-PAGE electrophoresis qualitative analysis found that black bean tempeh had deeper bands than unfermented sample <14.40 kDa,but a small part of <14.40 kDa protein was hydrolyzed during intestinal treatment of fermented samples.Degree of hydrolysis and the content of peptides below 10 kDa were increased and were significantly higher than those of unfermented black soybean(p<0.05),the peptide map further showed that the content and types of small molecular peptides of black bean tempeh were higher than those of unfermented black soybean at different simulated digestion stages.The ACE inhibitory activity of black bean tempeh was lower than that of unfermented black soybean,but the ACE activity increased after simulated digestion in vitro.Meanwhile,the exposed amino acid groups affect ACE inhibitory activity.In the whole process of simulated digestion in vitro,the total release of total phenol,total flavonoids and proanthocyanidins from black bean tempeh were 1.21 times,1.40 times and 1.55 times of thosefrom unfermented black soybean respectively.And the antioxidant capacity was significantly higher than that of unfermented black soybean(p<0.05).Besides phenolic compounds were significantly positively correlated with antioxidant activity(p<0.05).