Fermentation and complex enzyme hydrolysis for improving the total soluble phenolic contents, flavonoid aglycones contents and bio-activities of guava leaves tea

There are both soluble and insoluble-bound forms of phenolics in tea-leaf products. In order to increase total soluble phenolics contents, guava leaves tea (GLT) was first fermented with Monascus anka and Saccharomyces cerevisiae , and then hydrolyzed with complex enzymes . The changes in phenolics profiles, antioxidant activities and inhibitory effect on α -glucosidase in processed GLT were investigated. Compared with the un-fermented GLT, fermentation and complex enzymatic processing (FE) significantly increased the total phenolics, total flavonoids, quercetin and kaempferol contents by 2.1, 2.0, 13.0 and 6.8 times, respectively. After the FE, a major proportion of phenolics existed in the soluble form. Quercetin was released in the highest amount among different phenolics. In addition, soluble phenolic extracts from GLT following FE exhibited a highest antioxidant activity and inhibitory effect on α -glucosidase. The paper suggested an improved method for processing GLT into high-value products rich in phenolics and flavonoids aglycones with enhanced health benefits.