The effect of heating on the thermodynamic characteristics of potato starch

When potato starch was heated in excess water, individual starch granules differed with regard to their gelatinisation temperature. The DSC gelatinisation endotherm, however, represents the overall pattern for gelatinisation of all granules in the sample. The gelatinisation enthalpy is a combination of the endothermic disruption process of short- and long-ordered structures and the exothermic process of granular swelling. It was shown that the enthalpy for swelling was dependent on the gelatinisation conditions and that swelling and amylose leaching could be highly restricted by a leached amylose paste layer around the granule. For intermediate starch/water ratios, it is proposed that during heating the granules with the lowest gelatinisation temperature start to disrupt and swell first, followed by melting of the remaining intact granules, or their parts, when there is no free water remaining outside the granules. It is suggested that the very wide starch melting transition is related to the micro-heterogeneity of water distribution within the granule.