High pressure induced gelatinization of red adzuki bean starch and its effects on starch physicochemical and structural properties

Red adzuki bean suspensions (20%, w/w) were subjected to high hydrostatic pressure (HHP) processing at 0.1, 150, 300, 450 and 600 MPa for 15 min, and the effects of this physical modification on the physicochemical and structural properties were investigated. Scanning electron microscope and polarized light microscopy observation revealed a complete starch gelatinization after treatment with 600 MPa. HHP–treated samples displayed weak diffraction peak intensity compared to native granules revealed by X-ray diffraction analysis. The light transmittance was found to significantly decrease after HHP treatment, while syneresis increased with increasing HHP pressures. The increases in the solubility of HHP–pressured granules are associated with crystalline structures destruction and increasing granule swelling power, respectively. The DSC analysis showed an increase in onset and peak temperature, and a decrease in conclusion temperature, gelatinization enthalpy and gelatinization temperature range. RVA results suggested that HHP changes pasting features, particularly when treated at 600 MPa, resulting in a considerable decrease in peak, viscosity, breakdown and final viscosity, and an increase in pasting temperature and peak time. The results have shown that the physicochemical changes of HHP–treated starch granules are based on the structural destruction of granules.