Impact of heat-moisture treatment and annealing in starches: A review

Heat-moisture treatment (HMT) and annealing (ANN) are physical modifications that change the physicochemical properties of starch without destroying its granular structure. These hydrothermal treatments are processes in which the starch-to-moisture ratio, temperature, and heating time are critical parameters that need to be controlled. In HMT, starch is heated to temperatures above the gelatinisation temperatures but with insufficient moisture to gelatinise. In ANN, starch is exposed to excess water for an extended period of time at a temperature above the glass transition but below the gelatinisation temperature. The impact of such hydrothermal treatments on starch pasting, morphological, crystalline, thermal, and physicochemical properties, as well as on the enzymatic and acid susceptibility of starch will be discussed. The paper also highlights some applications of hydrothermally treated starch. This review is of significance not only for the development of novel starches for food and non-food applications, but also for understanding the impact of HMT and ANN on starch and its functionality.