Optimization of Cassava Starch Hydrolysis by Malt Extract, α-Amylase and Glucoamylase

Abstract

Cassava starch hydrolysis was investigated in this study using malt extract, alpha amylase and glucoamylase. The effects of process variables, namely: temperature, pH and time were studied and optimized for hydrolysis of cassava (Manihot esculenta) flour to glucose syrup. Three levels of process variables were used for the study. The three levels of process variables were: temperature (60, 67 and 74 oC), time (1.5, 2.0 and 2.5 h) and pH (4.5, 5 and 5.5). A polynomial regression model was developed using the experimental data. The results showed that production of reducing sugar was strongly affected by the variation of variables on malt extract, alpha amylase and glucoamylase hydrolysis of cassava starch. The fit of the model was expressed by the coefficient of determination R2 which was found to be 0.987 indicating that 98.7 % of the variability in the response can be explained by the model. The value also indicates that only 1.3% of the total variation is not explained by the model. This shows that equation (2) is a suitable model to describe the response of the experiment pertaining to reducing sugar production. The statistical significance of the model was validated by F-test for analysis of variance (p ≤ 0.05). For malt extract, alpha amylase and glucoamylase hydrolysis, the optimum value of temperature, time and pH were found to be 74 oC; pH 5.5 and time 1.5 h. The maximum reducing sugar production at optimum condition was 268 g/l representing 76.57 % conversion or 76.57 dextrose equivalent (DE)