Lactic acid fermentation of sweetpotato

Sweetpotato was saccharifed by the combination of amylolytic enzymes; alpha amylase and glucoamylase. Steamed and mashed sweetpotato was blended with enzyme solution at 1 : 2 ratio, w/w. The saccharification process was terminated after 90 minutes incubation at 55 deg C when 0.1 percent of alpha amylase and 0.15-0.2 percent of glucoamylase were used. When using 0.1 percent each of alpha amylase and glucoamylase, longer period of saccharification (up to 150-180 min.) was required to yield comparable amount of reducing sugars. Saccharified sweetpotato was subjected to lactic acid fermentation with a mixed cultures of Streptococcus thermophilus and Lactobacillus bulgaricus using 1 percent starter of each culture. The fermentation was carried out for 18-21 hours at 37 deg C. The resulted product socalled lactic fermented sweetpotato (LFSP) contained about 12 percent soluble solid; 0.7 percent acidity as lactic acid; 7 percent sugar and 6.8*10*[8) CFU/g viable cell count. It possessed slightly yellow color, relatively thick body with a pleasant aroma of cooked sweetpotato and acidic smell. The product could be blended with fruit juice such as orange juice of added with yogurt flavor to make a drinking yogurt-type beverage.