Biotransformation of phenolics and metabolites and the change in antioxidant activity in kiwifruit induced by Lactobacillus plantarum fermentation

BACKGROUND: Changes in antioxidant activity of fruit during fermentation are related to changes in the composition of phenolic acids and flavonoids. In this study, we investigated the effects of Lactobacillus plantarum on the phenolic profile, antioxidant activities, and metabolites of kiwifruit pulp. RESULTS: Lactobacillus plantarum fermentation increased scavenging activity of 1-diphenyl-2-picrylhydrazyl (DPPH) and 2,20-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radicals. The content of phenolics and flavonoids was increased after fermentation. Correlation analysis demonstrated that the phenolic and flavonoid content was responsible for increasing the scavenging activities of DPPH and ABTS. Lactobacillus plantarum influenced the phenolic profile of the pulp. Protocatechuic and chlorogenic acids were the predominant phenolic acids in fermented kiwifruit pulp. Gallic acid, chlorogenic acid, epicatechin, and catechins were degraded by L. plantarum. The content of 6,7-dihydroxy coumarin and p-coumaric acid, and especially protocatechuic acid, was increased by fermentation. Metabolic differences in lactic acid, fructose, phosphoric acid, gluconolactone, and sugar were evident between non-fermented and fermented kiwifruit. CONCLUSION: Lactobacillus plantarum fermentation increased antioxidant compounds and antioxidant activity in kiwifruit pulp. These results provide the foundation to target the functional benefits of L. plantarum-fermented kiwifruit pulp for further human, animal, and plant health applications. © 2020 Society of Chemical Industry.