Pasting viscosity and in vitro digestibility of retrograded waxy and normal corn starch powders

Pasting viscosity and in vitro digestibility of oven-dried powders of waxy and normal corn starch gels (40% solids) retrograded under an isothermal (4 degrees C) or temperature cycled (4/30 C) storage were investigated. Temperature cycling induced higher onset temperature for melting of amylopectin crystals than isothermal storage under a differential scanning calorimeter whereas little difference in crystalline type was observed under X-ray diffraction analysis. Temperature cycling caused higher pasting temperature and viscosity for the retrograded starches than isothermal storage. The retrograded waxy corn starch powders exhibited pasting behaviors similar to that of native waxy corn starch. However, the retrograded normal corn starch powders showed very much different pasting patterns with lower pasting viscosity but higher pasting temperature than native starch counterpart. The retrogradation increased slowly digestible starch content without changing resistant starch content, more effectively by the temperature cycling than the isothermal storage. (C) 2011 Elsevier Ltd. All rights reserved.