Abstract: In this study, the effects of fructooligosaccharides (FOS) on the chemical, microbiological and antioxidant properties of tamarind juice fermented by Lactobacillus plantarum A33 during fermentation and storage were investigated. FOS significantly increased the production of lactic acid and acetic acid during fermentation, with maximum yields of 3.12 and 0.34 g/L, which were 2.5 and 9 times higher than that of the blank group, respectively. FOS significantly increased the viable bacterial count up to 9.59 (lg(CFU/mL)), about 5.3 times higher than those of the blank group, and the total polyphenol content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity to 156.75 μmol/100 mL and 37.96 μmol Trolox equivalent (TE)/100 mL, respectively. During storage, the viable cell count decreased significantly in the control group, while it remained above 106 CFU/mL in the FOS group after 28 d of storage. FOS significantly improved the DPPH radical scavenging capacity of fermented tamarind juice during cold storage, resulting in the highest DPPH radical scavenging capacity of 44 μmol TE/100 mL on day 14. A total of 90 kinds of volatile components were found in the fruit juice, and 10 kinds of new volatile components were produced after 36 h of fermentation. The contents of most of the volatile components were decreased after 21 days of cold storage, while the content of characteristic substances in the juice was relatively stable, imparting a unique flavor to tamarind juice. The content of ethyl acetate continued to rise, making the flavor more refreshing. Our findings suggested that the flavor, viable cell count and antioxidant capacity of fermented tamarind juice could be improved by adding FOS before inoculation.

Key words: fructooligosaccharides; Lactobacillus plantarum; fermentation; tamarind juice; cold storage