Effect of starch-catechin interaction on regulation of starch digestibility during hot-extrusion 3D printing: Structural analysis and simulation study

Recent developments of hot-extrusion 3D printing (HE-3DP) have made it possible to manipulate starch digestibility. This work investigated the regulating mechanism of starch-catechin (EC) interactions on rice starch digestibility during HE-3DP by using modern analytical techniques and computational models. The results showed that the HE-3DP processing with starch-EC interactions could significantly decrease the starch digestibility (p < 0.05) due to the formation of ordered structures including short-range ordered structure, nano-aggregates and V-type crystalline structure. Meanwhile, molecular dynamics simulations were performed to reveal the mechanism of EC as an enzyme inhibitor to enhance the resistant starch contents of rice starch to 46.1%. Results showed that EC could loosely attach to starch chains, thereby facilitating binding to Trp59 of pancreatic α-amylase and preventing starch from binding to its active pocket. These findings provide useful structural information for EC to reduce starch digestibility in the HE-3DP environment.