Optimized Preparation of Porous Starch by Reactive Extrusion Combined with Enzymolysis

In this study, porous starch was produced by reactive extrusion combined with enzymolysis. In order to analyze the effect of variables on the oil absorption rate of porous starch, the process of preparing porous starch was optimized by the Placket-Burman design, the steepest ascent design and the Box-Benhnken design. Results showed that, four significant variables were screened out (moisture content, concentration of α-amylase, enzymolysis time, and concentration of glucoamylase) from nine related variables by Placket-Burman design. The maximum response area was determined by the steepest ascent design. The optimal parameter level of main significant variables was determined by Box-Benhnken design (BBD). An optimized formulation was as follows:The moisture of material was 36%, concentration of α-amylase was 0.52%, time of enzymolysis was 7.7 h, the concentration of glucoamylase was 1.73%, the temperature of barrel was 70℃, the speed of screw was 120 r/min, enzymolysis pH was 5.0, the temperature of enzymolysis was 50℃ and the substrate concentration was 25%, the oil absorption rate reached a maximum of 68.49%, which was similar to the measured value, and 14.97% higher than that of the control. The images of scanning electron microscopy demonstrated that, compared with the natural starch enzymolysis method, the combination of reactive extrusion and enzyme had obvious advantages in the number of pores, pore size and uniformity of distribution.