Changes in Nutrient Composition and Antioxidant Activity of Raspberry-Ferment during Fermentation

Abstract

Our objective was to determine the changes in nutrient composition and antioxidant activity of raspberry-ferment during fermentation. Changes of nutrient composition were determined using total phenolic compounds, soluble protein as well as total acidity. Reducing power and scavenging activities on hydroxyl radical and ABTS radical were investigated to test variations of antioxidant activity. The changes on nutrient composition and antioxidant activity of raspberry-ferment showed the time-dependent characteristics. After 48d fermentation, raspberry-ferment was increased to 2.72 mg/mL of total phenolic compounds, 2.90 mg/mL of soluble protein and 12.99 mg/mL of total acidity—about 22.0%, 74.7% and 246.4% more than the unfermented, respectively. Simultaneously, reducing power and scavenging activities on hydroxyl radical and ABTS radical were increased to 3.01 mg ascorbic acid equivalent (AAE)/mL, 15.04 mg AAE/mL and 1.95 mg AAE/mL respectively—about 50.5%, 7.0% and 17.8% more than the unfermented. During 48d fermentation, reducing power and scavenging activities on hydroxyl radical and ABTS radical were highly correlated with total phenolic compounds (r= 0.953, 0.943, 0.969, P<0.001, respectively). The results suggested that there might be some structural modification of components in raspberries due to enzymes liberated by bacteria and yeast and total phenolic compounds significantly contributed towards antioxidant activity during fermentation.