Effects Of Processing Methods On Antioxidant Activity And Physical And Chemical Properties Of Mung Bean Sprout Polyphenols

In order to maintain the antioxidant activity of polyphenols during processing of mung bean sprouts,a response surface was first designed to optimize the extraction process of mung bean sprouts polyphenols,and then compare the changes of polyphenol content and antioxidant activity during mung bean germination to determine the best germination period of mung bean.Finally,the best processing technology was determined by analyzing the influence of different processing methods on the polyphenol activity and physical characteristics of the best germination time of mung bean.The specific research results and conclusions are as follows:(1)The effects of extraction power,extraction temperature,extraction time,and the ratio of material to liquid in the extraction of mung bean sprout polyphenols in the ultrasonic microwave-assisted method were investigated,and the experimental conditions were optimized using response surface methodology.The results showed that the optimal extraction conditions were a material-liquid ratio of 1: 26,an ultrasonic time of 1 028 s,an ultrasonic temperature of35℃,and an microwave power of 422 W.Under this process,the extraction amount of mung bean sprout polyphenols was 24.12 mg GAE / g DW.The clearance rate of DPPH(extract concentration0.1)was 94.57%,and the clearance rate of ABTS · +(extract concentration 0.5)reached 94.54%.(2)By examining the effect of mung bean germination period on polyphenol content and antioxidant activity,the above process conditions were used to extract mung bean,bud length 0-1cm,bud length 1-2 cm,bud length 2-3 cm,bud length 3-4 cm,bud length of 4-5 cm,bud length of5-6 cm,and bud length of more than 6 cm Mung bean polyphenols at 8 stages of are determined by comparing the changes in polyphenol content,antioxidant activity,polyphenol composition and structure.Best mung bean sprouts.The results showed that the bud length of 4-5 cm was the best germination period.During this period,the polyphenol content was 28.59 mg GAE / g DW,which was 38% higher than before germination.The removal ability of mung bean sprout polyphenols to DPPH,hydroxyl radicals and total antioxidant capacity reached 93.82%,93.90%,8.32 U / mg,respectively,increased by 8.8%,34%,17.4% compared with before germination.During this period,mung bean sprout polyphenol compounds were the most abundant.33 out of 39 compounds that had been qualitatively detected,there are 11 kinds of isoflavones that have been qualitativelyidentified.The relative contents of daidzein and coumarone are the most abundant.Therefore,when the mung bean sprouts are 4-5 cm long,the content and antioxidant activity of the mung bean sprouts polyphenols can be maximized,and the composition of the mung bean sprouts polyphenols can be enriched.(3)Through examining the effects of processing technology on the content and antioxidant activity of mung bean sprouts.Three drying methods including hot air drying,combination drying and freeze drying,and four grinding methods of conventional grinding,ball milling,ultrafine grinding and airflow grinding were selected to process the mung bean germination period(4-5 cm in length),and the processing conditions were compared for the content of mung bean sprouts,the antioxidant activity,and influence of physical characteristics.The results showed that although the physical and chemical properties and microstructure of mung bean sprouts are best expressed after freeze-drying,the extraction of polyphenols is relatively low,and the DPPH and ABTS · +scavenging ability is weak.Combined with practical applications,the optimal processing conditions were a drying temperature of 45°C and air jet pulverization(working fluid pressure 0.5 Mpa,speed5,000 rpm).Under these conditions,the extraction amount of mung bean sprout polyphenols was31.65 mg GAE/ DW,DPPH,ABTS·+ and hydroxyl radical scavenging ability were 63.57%,89.06%,95.95%,physical indicators: median diameter(D50)11.36 μm,specific surface area 0.334m2/g,water content 4.00%,water activity(Aw)0.1455,Solubility 51%,bulk density 0.36 g/m L.In summary,this article aims at the problem of polyphenol loss and deactivation during the process of mung bean sprouts from germination to processing,and studies the changes of polyphenol activity during the sprouting,drying and processing of mung bean sprouts.It was found that the use of hot air 45℃,air-flow pulverization(working fluid pressure 0.5 Mpa,speed 5,000rpm)to dry and pulverize mung bean sprouts with a length of 4-5 cm can better maintain the polyphenol activity in mung bean sprouts.It will provide a theoretical basis for the maintenance of polyphenol activity in mung bean sprouts in the industrialized processing in the future.