Phenolics Profile, Antioxidant Activity and Flavor Volatiles of Pear Juice: Influence of Lactic Acid Fermentation Using Three Lactobacillus Strains in Monoculture and Binary Mixture

The aim of this study was to evaluate the effects of lactic acid fermentation using three Lactobacillus strains (Lactiplantibacillus plantarum 90, Lactobacillus helveticus 76, and Lacticaseibacillus casei 37) in monoculture and binary mixture on phenolics profile, antioxidant activity and flavor volatiles in pear juice. Results showed that the colony counts of binary mixture were higher than monoculture in fermented pear juice. The total content of phenols was increased, while that of flavonoids was decreased significantly during fermentation (p < 0.05). Antioxidant activities in fermented peer juice including DPPH and ABTS radical scavenging abilities and ferric reducing antioxidant power (FRAP) were significantly improved (p < 0.05). Binary mixture of Lactiplantibacillus plantarum 90 and Lacticaseibacillus casei 37 fermentation exhibited strong DPPH radical scavenging ability, due to the increase in vanillic acid and arbutin contents. Furthermore, lactic acid fermentation improved the formation of alcohols, esters, acids and terpenoids, and reduced the contents of aldehydes and ketones. Thirty new compounds including 15 alcohols, seven esters, five acids, and three terpenoids were observed in fermented pear juice. Hierarchical cluster revealed that flavor volatiles in pear juice were improved dramatically by Lactobacillus strains fermentation, and there were dramatic differences between monoculture and binary mixture.