Abstract: Objective: To study the effect of fermentation and processing on the antioxidant and hypoglycemic activity of mulberry fruit. Methods: The monosaccharide content, microbial populations and scavenging capacity against 2,2’-azinobis- (3-ethylbenzthiazoline-6-sulphonate) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, ferrous ion chelating power and alpha-glucosidase inhibitory activity of mulberry powder (MP), fermented mulberry (FM), freeze-dried fermented mulberry (D (FM)) and freeze-dried fermented mulberry mixed with soybean (D (FM + S)) were determined. Results: After fermentation and freeze-drying of mulberry, its fructose and glucose levels decreased to zero. The survival rates of Leuconstoc mesenteroides and Saccharomyces cerevisiae in D (FM) were 54.77% and 53.40%, respectively, while those in D (FM + S) were both more than 90%, implying that the presence of soybean resulted in reduced loss of probiotics during the freeze drying process. The ABTS radical scavenging capacity of these samples followed the decreasing order of D (FM) > D (FM + S) > MP > FM. Consistent trends were observed for DPPH and hydroxyl radical scavenging capacity and ferrous ion chelating power. Both D (FM) and D (FM + S) were ranked the highest, followed by MP, and FM was the weakest. The IC50 values for inhibition of alpha-glucosidase by MP, FM, D (FM) and D (FM + S) were 0.58, 0.53, 0.19 and 0.31 mg/mL, respectively, which indicates that the inhibitory effect of D (FM) and D (FM + S) was better than that of the other samples. Conclusion: Frozen-dried fermented mulberry mixed with soybean has stronger antioxidant and hypoglycemic effects than both fermented and unfermented mulberry.

Key words: mulberry, monosaccharide, microbial populations, antioxidant effect, hypoglycemic effect