Abstract: This study aimed to investigate the changes in the physicochemical properties and structural characteristics of a composite system comprising corn starch and zein at different addition levels under extrusion conditions and to analyze the interactions between the two components during the extrusion process. Corn zein was mixed with corn starch at different addition levels (0%, 2%, 4%, 6%, 8% and 10%), and processed using a twin-screw extruder at a screw speed of 150 r/min, a feed rate of 30 r/min, a moisture transportation flow rate of 9.7 mL/min (a material-to-liquid ratio of 2:1 (g/mL)), and eight extrusion temperatures zones (40, 60, 80, 110, 110, 110, 80, and 60 ℃). The results showed that extrusion disrupted the granular structure of starch, causing it to gelatinize and transit to an amorphous state. The addition of an appropriate amount of zein (8%) significantly improved the gelatinization, rheological and textural properties of the composite system, as evidenced by decreases in peak viscosity and retrogradation enthalpy, an increase in the proportion of bound water, decreases in hardness and adhesiveness, and an enhancement in springiness, resulting in the formation of a dense, continuous three-dimensional network structure. Additionally, it decreased the change in enthalpy of the composite system to its minimum level of 0.06 J/g, indicating a higher degree of starch gelatinization; the relative crystallinity decreased to 10.70%, the short-range order increased, and the crystal structure transformed from A-type to A + V-type. Further analysis indicated that starch and protein in the composite system interacted primarily via hydrophobic interactions and hydrogen bonding, effectively enhancing the physicochemical stability and processing performance of the system. This study provides an important theoretical foundation and practical guidance for the development of high-quality corn starch-based foods.

Key words: corn starch; zein; twin-screw extrusion treatment; interaction; physicochemical properties