The impact of heat-moisture treatment on molecular structures and properties of starches isolated from different botanical sources

Heat-moisture treatment is a hydrothermal treatment that changes the physicochemical properties of starches by facilitating starch chain interactions within the amorphous and crystalline domains and/or by disrupting starch crystallites. The extent of these changes is influenced by starch composition, moisture content and temperature during treatment, and by the organization of amylose and amylopectin chains within native starch granules. During heat-moisture treatment starch granules at low moisture levels (<35% water (w/w)] are heated at a temperature above the glass transition temperature (T(g)) but below the gelatinization temperature for a fixed period of time. Significant progress in heat-moisture treatment has been made during the last 15 years, as reflected by numerous publications on this subject. Therefore, this review summarizes the current knowledge on the impact of heat-moisture treatment on the composition, granule morphology, crystallinity, X-ray pattern, granular swelling, amylose leaching, pasting properties, gelatinization and retrogradation parameters, and susceptibility towards α-amylase and acid hydrolysis. The application of heat-moisture treatment in the food industry is also reviewed. Recommendations for future research are outlined.