| Abstract: | The objective of this research was to investigate the effect of heating rate at different moisture contents on starch retrogradation and gelatinization process. Starch retrogradation was not influenced by either moisture content (water/starch ratio of 0.7 or 2.0) or heating rate (5°C/min, 20°C/min, or 40°C/min). In order to further understand the effects of heating rate on starch–water interactions, starch suspensions at a water/starch ratio ranging from 0.7 to 3.0 were heated at 5, 15, or 25°C/min by using a DSC to different final temperatures and rescanned. The deconvoluted G and M1 endotherms and the corresponding additional unfrozen water (AUW) were determined. The results showed that the G and M1 endotherms merged at higher heating rates and at higher moisture contents as expected. A significant interaction was observed between moisture content and heating rate. The results suggest that the gelatinization process is governed by moisture content at the lower heating rate (5°C/min) and by heating rate at the higher heating rates (15 or 25°C/min). Results from the AUW data suggest that the M1 component of gelatinization dominated at moisture content below water/starch ratio of 1.5 and at 5°C/min heating rate. However, at moisture contents above water/starch ratio 1.0, an interaction was observed between moisture content and heating rate. The data suggest that at higher moisture content (>1.5 water/starch ratio) and at higher heating rate (≥15°C/min), there is still a kinetic limitation to the complete melting of the M1 endotherm. |
