Effects Of Steam Explosion On Different Bound Polyphenols And Antioxidant Activity In Red And Mung Beans

As an effective raw material pretreatment technology,steam explosion is gradually applied to the food industry.Red and mung beans are important grains,which are rich in polyphenols and are complex in composition,way of existence and binding form.Red and mung beans were pretreated by steam explosion with the pressure of 0.25,0.5,0.75 and 1.0MPa for 30,60 and 90 s,respectively.To study on the effect of steam explosion on different bound polyphenols content,the change of antioxidant activity and explore the correlation between them in red and mung beans.1?The effects of steam explosion on the microstructure in red and mung beans.After steam explosion,the raw materials had burst phenomenon and a large number of fragments.The surface area of raw materials increased and a large number of cavities were formed inside.It can promote contact between the active ingredients and the solvent in the raw materials,and facilitate the dissolution of polyphenols.The results showed that no new chemical structures and functional groups were generated in the raw materials after steam explosion by infrared spectroscopy.The absorption peak strength increased at the stretching vibration of hydroxyl group.2?The effects of steam explosion on the total polyphenols content(TPC),the total flavonoids content(TFC)and their antioxidant activity in red and mung beans.Extraction of polyphenols from raw materials by ultrasonic assisted extraction.The results showed that TPC and TFC in red and mung beans increased significantly after steam explosion.Under the explosion pressure of 0.5MPa for 60 s,the maximum TPC and TFC were detected in mung beans;however,the maximum TPC and TFC in red beans were detected at the pressure of 0.75 MPa for 60 s.Except under the conditions of 0.5MPa for 60 s,TPC and TFC in red beans were higher than that of mung beans.The changes of antioxidant activity were consistent with the changes of TPC and TFC,and the correlation between them reached a very significant level.The results of high performance liquid chromatography(HPLC)showed that the contents of epicatechin,gallic acid and ferulic acid in red beans increased significantly after steam explosion,and the contents of gallic acid,protocatechuic acid,p-coumaric acid,ferulic acid in mung beans.The contents of gallic acid,catechin,ferulic acid,p-coumaric acid and quercetin in red beans were higher than those in mung beans.3?The effects of steam explosion on different bound phenolic acids and their antioxidant activity in red and mung beans.Through alcohol extraction and alkali hydrolysis,the dried red bean and mung bean after steam explosion pretreatment were extracted to obtain different binding phenolic acids.The contents of free,ester-bonded,glycoside-bonded and methanol-insoluble phenolic acid in red and mung beans reached the maximum at the pressure of 0.75 MPa for 60 s and 0.5MPa for 60 s,after which it decreased.The results of HPLC showed that the contents of phenolic acids increased with steam explosion.In red beans,the content of coumaric acid in free phenolic acid was significantly increased,and ferulic acid in ester-bonded phenolic acid.In mung beans,the content of catechin in free phenolic acid increased significantly.The results of antioxidant experiment showed a similar rule with the change of phenolic acid content,the antioxidant activity of methanol-insoluble phenolic acid in red and mung beans was the strongest after steam explosion,and the scavenging capacity of ester-bonded phenolic acid was the weakest.The antioxidant capacity of phenolic acid in red beans was higher than that in mung beans.4?The effects of steam explosion on anthocyanins and their antioxidant activity in red and mung beans.The anthocyanin in raw materials was determined by n-butanol-hydrochloric acid method.The results indicate that the contents of anthocyanin decreased with steam explosion,except under the conditions of 0.25 MPa for 30 s.The results of HPLC showed that the contents of delphinidin and cyanidin in the two samples were slightly higher than those in the control group at 0.25 MPa for 30 s.The antioxidant activity of the extract of red beans was higher than that of mung beans.There was a significant correlation between the content of delphinidin,cyanidin,total anthocyanin and their antioxidant activity in red and mung beans.