Effects of various physical pretreatments and dextranase on the structure and physicochemical properties of porous sweet potato starch: a comparative study

Porous starch is a type of modified starch that contains a high number of tiny micropores. Due to its natural absorbent properties, porous starch has broad application prospects. Currently, enzymatic hydrolysis is predominantly used for production of porous starch, however, the hydrolysis efficiency is relatively low. In this study, sweet potato porous starch was prepared by combining physical pretreatments with dextranase, and then its adsorption properties were investigated. Ultrasonic, moist heat, and microwave pretreatment methods were used, and the structure, physicochemical properties, and adsorption capacity of resulting porous starches were detected. The microwave-combined enzymatic hydrolysis resulted in a porous starch with more compact pore structure in a shorter time. Additionally, no new chemical groups were observed in the porous starch. The treatment not only increased the solubility of starch to 5.22%, but likewise reduced the swelling power to 6.92%. Furthermore, adsorption capacity of the starch improved remarkably due to increased porosity and specific surface area. Specifically, the oil absorption improved from 51.02 to 102.79%, while the water absorption improved from 58.63 to 120.40%. This study provides an efficient method to produce porous starch from sweet potato with enhanced water and oil absorption capacity, which has promising applications in the food and pharmaceutical industries.