Starches can be physically modified through moist heat treatment and annealing, resulting in heat-moisture-treated starches (HMT starch) and annealed starch. HMT starch has a higher gelatinization temperature, less granule swelling, and less amylose leaching than native starches due to increased thermal stability. Annealing involves heat and water treatment at low temperatures and high water to starch ratio, which leads to a physical reorganization of starch granules. This treatment generally increases moisture content, decreases the starch’s solubility and SP (swelling power), and slightly reduces the PT (pasting temperature) while increasing the endothermic temperatures and enthalpies of the starch samples.
Films made of HMT starch exhibit higher tensile strength and puncture energy, but lower solubility compared to native starch films. (da Rosa Zavareze & Dias, 2011).