Molecular dynamics insights into the interaction mechanism between starch with tea polyphenols and its impact on the rice noodle quality

The starch-polyphenol complexes have been extensively studied, but interaction mechanisms between starch and the specific monomer of tea polyphenols (TP) and the modulatory effect on the quality characteristics of rice noodles requires further investigated. In this work, a comparative analysis on the structures and quality characteristics of TP-fortified rice noodles derived three typical indica rice cultivars (Hly 16, Ly 6176, and Zz 83) was conducted, among which Zz 83 was further selected to assess the complexation mechanism between starch and four major TP monomers (EC, EGC, ECG, and EGCG). The results showed that the formation of starch-TP complexes improved the gel properties, in which Zz 83 with TP exhibited the highest final viscosity and setback value. The network structures of rice noodles became loose and cross-sectional pores were larger upon adding TP. Rice noodles prepared by Zz 83 with TP added (Zz 83-TP) exhibited the best quality performance, which showed increased hardness (2638.93 g) and lowest cooking loss (7.19 %). TP significantly inhibited starch hydrolysis rate, while Zz 83-TP showed the strongest anti-digestibility with the hydrolysis index of 45.60 % and eGI value of 64.74. The binding capacity of galloylated catechins (EGCG, ECG) to starch was significantly higher than that of non-galloylated catechins (EGC, EC) with affinity rankings as EGCG > ECG > EGC > EC. EGCG could effectively induce starch the V-type single helical structures with the relative crystallinity of 19.38 %. This study provides a theoretical basis for the development of starch-based food design with low digestibility.