Secondary metabolite profiles and bioactivities of red raspberry juice during fermentation with Wickerhamomyces anomalus

Abstract

Raspberry contains a broad array of valuable phytochemicals and therefore has positive effects on health. Fermentation can transform these components. The variations in the secondary metabolite profiles and bioactivities of red raspberry juice during Wickerhamomyces anomalus fermentation remain unknown. Herein, the effects of W. anomalus on the secondary metabolites, other constituents (total sugars, reducing sugars, and total acids) and bioactivities of raspberry juice were investigated. The fermentation significantly decreased the level of total sugars, reducing sugars, total acids and anthocyanins, but greatly increased the content of polyphenols and flavonoids. The antioxidant capacity and α-glucosidase inhibitory activity of raspberry juice were markedly enhanced after fermentation, whereas the cholesterol esterase inhibitory activity was reduced significantly. Moreover, 721 secondary metabolites were identified, wherein 437 secondary metabolites (240 upregulated, 197 downregulated) were selected as differential metabolites via targeted metabolomics. A total of 89 secondary metabolites were annotated in the Kyoto Encyclopedia of Genes and Genomes pathways, most of which were matched to biosynthesis of secondary metabolites and metabolic pathways. Phenolic acids were mainly transformed via phenylalanine metabolism and tyrosine metabolism. These results can provide reference for the development of functional raspberry beverages.