Preparation of products rich in resistant starch from maize starch by an enzymatic method

We prepared resistant starch (RS) from maize starch using a method combining alpha-amylase and pullulanase. We optimized reaction conditions for alpha-amylase, including temperature (T), pH, reaction time (t), and amount of alpha-amylase. The highest formation of RS (58.87%) was obtained under the following conditions: temperature, 90 degrees C; pH, 5.5; time, 15 min; and amount of alpha-amylase, 4 mu/g. Scanning electron microscopy and differential scanning calorimetric analyses showed that maize starch underwent pasting treatment with alpha-amylase contained shorter amylase chains, and decreased steric hindrance among molecules compared with native maize starch. It is advantageous for amylopectin to be debranched by pullulanase, and the short amylose chains released from amylopectin can form double helices. Compared with native maize starch, maize RS showed increased crystallinity, and a larger, more compact laminiplantation structure. The increased density of the crystals greatly increases their resistance to starch-degrading enzymes. This is a promising method for preparing RS-rich products. (C) 2011 Elsevier Ltd. All rights reserved.