Nutritional and Flavor Characteristics of Lactobacillus rhamnosus Fermented Goji Berry Juice and Its Antioxidant Activity and in Vitro Inhibition of Xanthine Oxidase Activity

The dried fruit of Ningxia goji berry (Lycium barbarum L.) with the homology of medicine and food was used as raw material, and fermented by Lactobacillus rhamnosus to prepare fermented goji berry juice in this study. The fermentation process was optimized by one-way and response surface experiments using the inhibition rate of xanthine oxidase as the evaluation index. The fermentation characteristics, nutritional and flavor properties, and antioxidant activities of the fermented goji berry juice were investigated. The results showed that the optimal fermentation process for the fermentation of goji berry juice by Lactobacillus rhamnosus was 28 h of fermentation time, 34 ℃ of fermentation temperature and 4% of inoculum. Under these conditions, the inhibition rate of xanthine oxidase by fermented goji berry juice was 79.40%, the pH value of fermented goji berry juice was 4.44±0.04, and the number of viable bacteria could reach 9.5±0.005 lg CFU/mL. Compared with unfermented goji berry juice, the content of soluble protein, total phenols, and total flavonoids in fermented goji berry juice was significantly reduced (P<0.05), while the total sugar content was increased. In addition, the GC-IMS analysis results showed that more alcohol substances were produced in goji berry juice after fermentation, which increased its unique fermentation aroma. The results of in vitro antioxidant activity analysis showed that the DPPH free radical scavenging ability of fermented goji berry juice significantly increased by 186.5% (P<0.05).