Optimization of pullulanase hydrolysis technology in processing modified extrusion starch films

In order to enhance the mechanical properties of the biodegradable corn starch films, the pullulanase and extruded corn starch were used to prepare films. Optimized technology for preparing biodegradable film was studied by the central composite rotatable design with five variables of pH, temperature, time, the dosage of pullulanase and extruded corn starch. The tensile strength of film was as the evaluation index. The results indicated that the effect order of five factors on the tensile strength of film was as follows: dosage of extruded starch, dosage of pullulanase, time, pH, temperature. With 46.57℃ reaction temperature, 4.44 pH, 6.63 u/g pullulanase, 9.31 h reaction time and 7.00% extruded corn starch, the predicted value of the film tensile strength was the highest (24.3654 MPa), whereas, the experimental value was 24.2539 MPa, which increased by 338.01% compared with the native corn starch film. The RSM-predicted tensile strength and the experimental tensile strength of modified extrusion starch films were not significantly different from each other. The results showed that the empirical model developed by response surface methodology was adequate to describe the relationships between the factors and response values. The tensile strength of modified extrusion corn starch film had extra significantly positive correlation with amylose content of modified extrusion starch (r = 0.863, P＜0.01).