Antioxidant activity and optimal manufacturing conditions of purple sweet potato lactic acid bacteria drink

In the current studies, we produced a purple sweet potato lactic acid bacteria drink (PSPLABD) using a variety of lactic acid bacterial strains. The various PSPLABD were analyzed for color, pH, and flavor. We found that Lactobacillus helveticus B-1 was the most efficient strain for fermentation. In addition, optimal conditions included a purple sweet potato content of 10%, a skim milk content of 7%, a white sugar content of 7.5%, fermentation at 35°C, and a pH adjusted to 3.5 (fermentation time ∼24 h). PSPLABD had 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity (IC50 = 130 μl) and inhibited lipid peroxidation (equivalent to 103 μM butylated hydroxytoluene). Fermentation had no effect on the antioxidant activity of PSPLABD, but the purple sweet potato and the lactic acid bacteria drink components had a synergistic effect on the inhibition of lipid peroxidation. Thus, the PSPLABD could be used as a health food which has antioxidant activity and an appealing flavor and color.