Development And Antioxidant Activitiy Evaluation Study Of Oligosaccharide-supplemented Lycium Barbarum Fermented Beverage

Lycium barbarum L.(LB),as a dual-purpose crop for both medicine and food,has extensive applications in the food processing industries.In the current industry of LB,the processing conversion rate of LB is low,and there are fewer deep processing products.It has been shown that the fermentation of LB beverages by lactic acid bacteria(LAB)increases the content of bioactive substances,thus improving the nutritional value of the product.However,the process parameters of oligosaccharide-added fermented beverages of LB have been less studied.The changes of polyphenols,flavonoids and other components and antioxidant activities in the fermented beverages are not clear.Therefore,this study used dried LB as the research material and Lactobacillus rhamnosus(LR)and Lactobacillus plantarum(LP)as fermentation strains,supplemented with galactooligosaccharides(GOS)and fructooligosaccharides(FOS).Through single-factor experiments and optimization experiments,the process parameters for fermented oligosaccharide LB beverages were determined.Based on this,the changes in the main antioxidant components and antioxidant activities were analyzed,as well as the changes of on their viable count and antioxidant activities during in vitro digestion and storage.The specific experimental content and results are as follows:(1)The optimal conditions for preparing LB fermentation beverages were obtained:a material-to-liquid ratio of 1:6 for dried LB to water,a ratio of 1:4 for GOS to FOS,a ratio of2:1 for LR to LP,and a fermentation temperature of 37°C.The suitable stabilizer combination for improving the precipitation of oligosaccharide LB fermented beverage was determined:gum arabic,carboxyl methyl cellulose Na,xanthan gum and guar gum were added at 0.09%,0.08%,0.06%and 0.09%,respectively.Under these conditions,the centrifugal precipitation rate decreased from 7.53%to 2.79%.The resulting product showed no detection of Escherichia coli or mold,with a LAB count of 8.89×10~8 CFU/m L and an acidity level of 8.31g/L.(2)After the addition of FOS and GOS,the total LAB viable count in the LB beverage at the fermentation endpoint increased by 3.45×10~8 CFU/m L compared to the LB beverage without oligosaccharides,with an acidity increase of 2.73 g/L.During fermentation,the content of FOS decreased by 0.93 g/100 g.Compared to the unfermented LB beverage,the oligosaccharide addition increased the total phenolic,flavonoid,and carotenoid contents of the fermented LB beverage by11.0%,26.6%,and 14.3%.Meanwhile,the DPPH radical scavenging activity increased by 14.9%,the total reducing power increased by 16.9%.(3)During the in vitro simulated digestion process,the content of antioxidant substances and antioxidant activity in LB beverages significantly decreased.The bioaccessibility of total phenols,total flavonoids,carotenoids and crude polysaccharides in the oligosaccharide-supplemented LB fermented beverage reached 40.8%,44.3%,45.1%,and 80.0%,respectively,with minimal loss of antioxidant activity.During storage,the LAB count in the LB fermented beverage decreased,with a survival rate of only 36.7%,while the addition of oligosaccharides significantly increased the LAB survival rate to 67.5%.