Regulation mechanisms of starch molecular structure on gel properties and rice noodle quality

The starch molecular structure is crucial for rice noodle manufacturing, however, the intrinsic mechanism by which starch molecular structure regulates the gel properties and quality of rice noodles remains unclear. Here, the regulatory mechanisms were investigated using six rice cultivars with apparent amylose content (AAC) of 19.84%-25.82%. Results revealed that the rice with high AAC was associated with superior sensory scores and uniform moisture distributions in noodles. AAC was positively correlated with water absorption rate, hardness, and chewing index, while negatively correlated with optimum cooking time and broken strip rate. The fa chains (DP 6-12) of amylopectin showed a negative correlation with water absorption rate, while fb₁ chains (DP 13-24) showed the opposite correlation. Additionally, fb₃ chains (DP 37-100) were negatively related to hardness. Short-chain amylose (100 ≤ X < 1000) was negatively correlated with adhesiveness and positively correlated with chewing index. For 1000 ≤ X < 2000, there was a negative correlation with hardness, chewing index, and sensory score, while being positively correlated with broken strip rate and adhesiveness. The 2000 ≤ X < 20,000 was positively correlated with adhesiveness and negatively correlated with chewing index. Amylose content and chain length distributions regulated gel formation and noodle quality by controlling the cold paste viscosity, setback viscosity, crystalline structure, and gelatinization temperature. Rice cultivars with higher proportions of fb₁ and short-chain amylose of 100 ≤ X < 1000 performed better in noodle production, contributing to higher hardness, chewing index, water absorption rate, while exhibiting lower adhesiveness and broken strip rate. These findings elucidated the connections between molecular structure of starch, supramolecular structure of gels, and macro qualities of noodles, providing new perspectives for selection and breeding of rice cultivars suitable for noodle production.