New insights into the effects of starch-oleic acid-chlorogenic acid interactions on structural formation by hot-extrusion 3D printing: From perspective of nonlinear rheology

Abstract

Nonlinear rheology can be used to monitor the molecular chain movement of polymer materials under large strain conditions. In this work, we firstly set up large amplitude oscillatory shear (LAOS) conditions simulating the hot-extrusion 3D printing (HE-3DP) process and attempted to match the structural formation of wheat starch (WS) by starch-oleic acid (OA)-chlorogenic acid (CA) interactions during HE-3DP from perspectives of nonlinear rheology. Results showed that when compared with WS system, the b value and zero-strain nonlinearity (Q0) of WS-OA system increased with OA addition, and it exhibited obvious strain hardening and shear thinning behaviors, which were ascribed to that OA interacted with starch to form single helix and V-type crystalline structure through hydrophobic force, and it obstructed the integrality of gel network. For WS-CA system, the b value and Q0 decreased with CA addition and the shear thickening behavior was increased which could be explained that CA interacted with starch chains through hydrogen bonding following the formation of aggregates structure, thus improving the integrity of network structure. Notably, when compared to above two binary systems, the early emergence of strain thickening and the weakening of strain stiffening for WS-OA-CA system declared that CA contributed to inhibiting the aggregation and assembly of the single helix formed by WS-OA interactions. Overall, this study provided important information for the application of nonlinear rheology in the structure evolution of starch system during HE-3DP.