Abstract: In this paper, blueberry fruit slurry was inoculated with Lactobacillus acidophilus, L. casei or L. paracasei for fermentation. Changes in the contents of free and bound polyphenols and proanthocyanidin composition as well as the antioxidant activity of polyphenols were monitored before and after fermentation. The results showed that fermentation with L. paracasei and L. casei significantly increased the contents of blueberry polyphenols, and all three species of lactic acid bacteria (LAB) significantly decreased the content of free proanthocyanidins. LAB fermentation also had a great impact on the contents of 9 characteristic phenolic acids and 3 proanthocyanidin monomers; the three species all increased the contents of protocatechuic acid, vanillic acid, syringic acid, catechins and quercetin, especially the last one, which was extremely significantly increased, while the content of proanthocyanidins B1 was significantly increased exclusively by fermentation with L. paracasei. Antioxidant tests showed that fermentation with L. paracasei significantly enhanced the ability of blueberry polyphenols to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation, and L. casei also improved the scavenging ability of ABTS radical cation. Collectivley, compared with the other two strains, L. paracasei could better improve the content and antioxidant activity of polyphenols in blueberries. This study provides a reference for the development of fermented blueberry beverage.

Key words: lactic acid bacteria; blueberry; polyphenols; proanthocyanidins; antioxidant activity