Heat-stable single-helical structures formed during the extrusion process play a key role in the cooking and texture qualities of rice noodles

Extrusion is a critical process in rice noodle production. However, the underlying mechanism by which it influences noodle quality remains inadequately understood. In this study, rice noodles were processed at extrusion temperatures ranging from 100 °C to 140 °C and characterized in terms of molecular structure, short- and long-range order, microstructure, cooking loss, and texture properties. The results indicated that extrusion at 120 °C promoted the formation of heat-stable amylose single-helical structures, including V_II-type crystals. These stable amylose structures reduced their interference with the rearrangement of amylopectin, facilitating the formation of amylopectin double-helical structures and A-type crystals during the subsequent retrogradation process. The highly ordered helical structures and crystals were further organized into larger, denser domains, characterized by a gyration radius of 21.45 nm, a fractal dimension of 2.54, and a correlation length of 6.64 nm. These dense domains were uniformly distributed throughout the gel matrix of rice noodles, acting as cross-links within the gel network and thereby enhancing its mechanical strength. The enhancement in the gel's mechanical strength ultimately contributed to improved eating quality of rice noodles extruded at 120 °C compared to those extruded at 100 °C. This improvement was evidenced by a 53.4 % reduction in cooking loss, a 52.5 % decrease in adhesiveness, and significant increases in hardness (51.4 %), springiness (21.3 %), and chewiness (52.3 %). This study underscores the critical role of heat-stable amylose single-helical structures, particularly V_II-type crystals, formed during the extrusion process in determining the cooking and texture qualities of rice noodles.