Effect of Heat-moisture Treatment on the Properties of Sweet Potato Starch

To explore the effects of heat-moisture treatment on the physicochemical and structural properties of sweet potato starch, five types of sweet potato starch were used as the raw material, and their solubility, swelling power, water holding capacity, transmittance, and sedimentation were determined. Furthermore, the influence of heat-moisture treatment on the water absorption characteristics, particle morphology, and crystal structure of sweet potato starch with different initial water contents was explored. The results showed that the solubility, swelling power, retrogradation, and transmittance of the five sweet potato starches treated with heat-moisture were all decreased when compared with the original starch, but their water holding capacity was increased. The surface of sweet potato starch particles treated with heat moisture showed obvious dents, pores, and cracks, without any new diffraction characteristic peaks. The crystal type of those treated starch remained a C-type structure, but the diffraction intensity and crystallinity were decreased, indicating that heat-moisture treatment could effectively improve the structural characteristics of sweet potato starch. Moreover, the higher the initial moisture content of sweet potato starch, the faster the water absorption rate of sweet potato starch after heat-moisture treatment. The time required for the heat-moisture treated starch to reach equilibrium in water absorption was shorter than that of the original starch, and the saturated water absorption tended to decrease compared to the original starch. The soaking kinetic constants K₁ and K₂ from the Peleg model equation were calculated, and the water absorption kinetics equation of sweet potato starch after wet heat treatment was confirmed, achieving accurate prediction of its water content during the soaking process.