Preparation of citrate-esterified corn starch via synergistic enzymatic debranching and infrared radiation: Physicochemical properties, multilayer structure and mechanism

Citric acid-esterified corn starch with high resistance to digestion was prepared by synergistic enzymatic debranching (ED) and infrared irradiation (IR). The effect and underlying mechanism of the synergistic interaction between ED and IR were evaluated through an analysis of the physicochemical characteristics and hierarchical structural features of the modified starch samples. Compared with IR-modified starch (IRS), the synergistic sample (SEDIR) showed superior thermal stability (no gelatinization at 95 °C), a significantly reduced Rapid Visco Analyzer (RVA) recovery value of 4.05 mPa·s, and a 35% increase in resistance to digestion. These improvements were attributed to ED disrupting the branched structure and exposing hydroxyl groups, which facilitated subsequent IR esterification and increased substitution degree. Hydrolysis and digestion rates followed the order of native corn starch (NS) > IRS > EDS > SEDIR, indicating that ED promoted amorphous degradation, while IR enhanced steric hindrance, delaying enzymatic digestion. Overall, ED followed by citric acid–IR esterification represents an efficient approach for preparing high- resistant starch starch with promising applications in the food industry.