Effect of starch molecular structure on texture and digestibility of freshly cooked and retrograded rice noodles

This study investigated the relationship between starch molecular structure, texture, and digestion characteristics of Chinese rice noodles. A total of 4 types of rice flour with varying amylose content were selected as model materials, and the digestion characteristics of freshly cooked and retrograded rice noodles were compared. The texture and digestibility of the noodles were found to be closely associated with the molecular structures of the rice starches. A balanced hAP2/hAP1 (ratio of the peak heights of amylopectin) ratio (0.73) and intermediate amylose content contributed to greater hardness and springiness, while starches with lower molecular weights were associated with increased adhesiveness. Regarding digestibility, although amylose content was negatively correlated with digestibility (with the highest-amylose sample, 31%, showing the lowest digestibility at 80%), it was not the sole determinant. Fine molecular features, such as starches with less short amylose chains (100 < X ≤ 500) and a higher degree of branching (7.3%), was found showed a higher digestible ratio while lower digestion rate. Retrogradation slightly reduced the digestibility of rice noodles, affecting both the digestible ratio and rate. This work provides a reference for selecting suitable rice varieties and flours for use in traditional Chinese rice noodle production, offering insights into quality control and nutritional optimization.