Effect Of Enzymatic Hydrolysis Combined With Multi-strains On Fermentation Characteristics Of Lycium Barbarum Beverage During Fermentation

In recent years,consumers have increasingly favored lactic acid fermented foods because lactic acid fermented foods have a nutritional health effect.As a traditional medicine and food homologous food,the deep processing and utilization of lycium barbarum has always been the focus of people's attention and research.At present,the pretreatment of lycium barbarum is dominated by a single enzymolysis treatment,and the research on ultrasonic assisted enzymolysis treatment and complex enzymolysis is still blank.And because the flavor of the lycium barbarum itself is unpleasant,the fermentation has a great advantage in improving the taste and flavor of the product Therefore,the enzymolysis technology combined with microbial technology has been applied to the development of lycium beverage.Furthermore,the main component changes and antioxidant activities in the fermentation process of the products were studied,in order to provide a theoretical basis for the development of new type of fermented beverages.The specific research contents and results are as follows:(1)The PB test of ultrasonic synergistic double enzyme enzymolysis of mash was combined with response surface methodology to optimize the study.Taking lycium barbarum as raw material,the ratio of pectinase and ceIlulase,enzymolysis temperature,enzymolysis time,the ratio of material to water and enzyme addition amount were used as the factors to test the juice yield.On the results of the single factor test,the PB test was used to screen out three factors that have a great influence on the juice yield of the lycium barbarum:temperature,time,and enzyme addition amount are the variables of the response surface model design.Combined with the BBD design-response surface method,The optimum technology of lycium barbarum juice enzymolysis was optimized:enzymolysis temperature 50°C,enzymolysis time 60 min,enzyme addition amount 1.6%,under which the average juice yield of the Lycium barbarum juice is 96.477%.(2)Study on the dynamic changes of main components of fermented lycium barbarum beverages by different lactic acid bacteria.The Lactobacillus plantarum,Lactobacillus rhamnosus and Lactobacillus thermophilus strains were activated,and their growth curves,acid production ability and acid and bile salt resistance were measured.The results showed that the three strains entered the stable growth period at 12 h,10 h and 8 h respectively.After 12h,the acidity of the three strains was mild,the Lactobacillus thermophilus was maintained at 4.5,and the Lactobacillus plantarum and Lactobacillus rhamnosus remained at about 3.7.The three strains have better acid resistance and stronger ability to resist bile salts.Then,the natural fermentation was used as the control group,and the single and composite lactic acid strains were used as the experimental group.The dynamic changes of themain components of fermented lycium barbarum beverages during the fermentation were analyzed.The main indicators were reducing sugar,pH value,total acid and volatile compounds.(3)Based on uniform design and principal component analysis,the process optimization of lycium barbarum beverage fermentation was studied.The processing technology of the beverage fermentation was optimized by a combination of single factor test and uniform design test.hrough the principal component analysis,the four indicators showed that the main indicators for determining the size of the first principal component were carotenoids and total sugars;the indicators for determining the size of the second principal component were mainly total acids and total phenols.The preferred fermentation process by partial least squares regression analysis is:the inoculum amount Xi is 2.5%,the fermentation temperature X2 is 30?,and the fermentation time X3 is 40 h.(4)The main component analysis and antioxidant activity changes of lycium barbarum beverages in different fermentation methods.By studying the changes of the content of each product in the fermentation of lactic acid bacteria and yeast,To explore the changes of main components and antioxidant activities in the mixed fermentation of lycium barbarum beverage by lactic acid bacteria and yeast and the fermentation of lycium barbarum beverage by lactic acid bacteria and then the fermentation of lycium barbarum beverage by yeastFurthermore,SPSS software was used to analyze the correlation between antioxidant activity and main components,to explore the correlation degree,and to establish a regression model.The results showed that the changes of main components and antioxidant activities of lycium barbarum beverages were basically the same in the two different fermentation modes,but the content of main components and antioxidant activity of lycium barbarum beverage were higher after lactie acid bacteria fermentation and then inoculated yeast fermentation.Some nutrients may be lost during the fermentation of the beverage,but the antioxidant activity of the fermented beverage is still relatively high.The results showed that the main components of the fermented beverages,total phenols and total flavonoids,were significantly positively correlated with DPPH free radical scavenging rate,ABTS free radical scavenging rate and hydroxyl radical scavenging rate,and negatively correlated with superoxide free radical scavenging.After fermentation,the volatile substances in the fermented beverages were significantly improved,and the main increase was alcohols and esters.