Physicochemical and pasting properties of corn starch as affected by hydrothermal modification by various methods

Native corn starch has a lack of characteristics such as low thermal stability, low resistance to shear force, and a high tendency to retrograde. To address this problem, it needs to be modified to improve its application in the food sector. Hydrothermal modification is one of the physical modifications by heating the starch above the gelatinization temperature with a limited water content. In this study, native corn starch was modified using various methods of hydrothermal modification which did not cause full gelatinization of starch and maintained starch granule integrity i.e., heat-moisture treatment (HMT), autoclave-heat treatment (AHT), microwave-heat treatment (MHT), and osmotic-pressure treatment (OPT). HMT, AHT, and MHT were modified by limited moisture content (30%) and then was heated using an oven, autoclave, and microwave, respectively, while OPT was heated in Na2SO42- solution using an autoclave. The results showed that the thermal modification did not alter the A-type crystallinity pattern of its native starch, but an amylose-lipid complex occurred resulting A + V-type crystallinity pattern. AHT starch has the highest V-type peak which indicated the highest amylose-lipid complex. The relative crystallinity increased after modification treatment except for OPT. The thermal modification increased thermal stability and increase the retrogradation ability of native corn starch. Parameters of thermal characteristics such as To, Tp, and Tc increased and Range of Tc – To decreased (except for HMT) after thermal modification. Solubility, water absorption capacity, gel strength, and syneresis of native corn starch tend to increase after modification. The best thermal modification of corn starch was OPT because it can produce the modified starch that not only had the highest thermal stability but also a lower retrogradation ability, the lowest swelling volume, higher water absorption capacity, and gel strength. Therefore, the hydrothermally modified corn starch could be applied to canned food, noodle, and bakery.