The effect of size and solid content in hydrolysis of sweet potato starch using endogenous beta-amylase enzyme

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Sweet potato contains significant amount of endogenous amylase enzymes. The endogenous enzymes can be used in maltose production from sweet potatoes to carry out pre-hydrolysis of the starch to some extent, follow by complete hydrolysis using external enzymes. The main objective of the current study is to investigate the effect of particle size and solid to liquid ratio in hydrolysis process of sweet potato starch using endogenous enzymes. The extent of hydrolysis process is measured by dextrose equivalent of the crude maltose solution. Hydrolysis process consists of liquefaction and saccharification process. The liquefaction process is carried out at 71.5°C and pH 6 for 25 minutes while saccharification process is carried out at 53°C and pH 5,5 for 72 hours. Dextrose equivalent is measured using Lane-Eynon method. The results show that the access of enzyme to the potato tubers is the key to hydrolysis process. The smaller size of tubers gives bigger surface area while lower solid-to-liquid ratio increases enzyme mobility but decreases sugar concentration. Base on the results, a simulation shows that the pre-hydrolysis of sweet potatoes using endogenous enzymes can save almost a half of enzymes required for traditional hydrolysis process.