Effect of Lactic Acid Bacteria on Antioxidative Activity of Sweet Potato Yogurt

Abstract

H. E. MILLER's method was modified to evaluate the antioxidative activity (AA) of sweet potato yogurt (SPY). The strength of the AA was converted into BHT (Butyllhydroxytoluene) concentration (10-200μM) by the modified method. Nine species of lactic acid bacteria were tested by the method to examine the influence of the bacteria on the AA of SPY. The AA of SPY fermented with IFO3070, IFO3182, IFO3202, IFO3427 and IFO13957 did not increase at all. On the other hand, the AA of SPY made with IFO3425, IFO3533, IFO13953 and IFO15883 increased greatly due to the lactic acid fermentation. Finally, the AA of SPY made with IFO13953 (Lactobacillus delbrueckii subsp. bulgaricus) was the highest. The AA of SPY fermented IFO3425, IFO3533 and IFO15883 started to increase after a lag phase of 2 or 3 days. However, the AA of SPY fermented with IFO13953 increased rapidly during the fermentation, without lag phase.