The Influence of Amylose and Amylopectin Characteristics on Phase Transition of Cornstarches Observed under Shearless Condition

The influence of amylose and amylopectin characteristics on phase transition of cornstarches under shearless condition was observed by SEM and CLSM. The change of internal structure of starch granules during heating were directly observed online. Brightness of starch granule indicates the degree of gelatinization. The brightness of all the starches decreased with increasing temperature, this change being initiated at the centre of granule. Thus it is clear that the gelatinization process starts at the hilum of the granules. The central area of the granule around the hilum is believed to be the least organized region. The granules of waxy maize and normal maize starch subsequently break through at their cavity and channels, when the granules became swollen during gelatinization, whilst the granules of G50 and G80 remain granular and break down to smaller pieces.