Lactic Acid Fermentation of Sweetpotato

Abstract

Sweetpotato was saccharified by the combination of amylolytic enzymes; alpha amylase and glueoamylase. Steamed and mashed sweetpotato was blended with enzyme solution at 1:2 ratio, w/w. The saccharification process was terminated after 90 minutes at 55ºC when 0.1% of alpha amylase and 0.15-0.2% of glucoamylase were used. When using 0.1% 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% starter of each culture. The fermentation was carried out for 18-21 hours at 37ºC. The resulted product socalled lactic fermented sweetpotato (LFSP) contained about 12% soluble solid; 0.7% acidity as lactic acid; 7% sugar and 6.8x10⁸ 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 or added with yogurt flavor to make a drinking yogurt-type beverage.