An insight into the structural evolution of waxy maize starch chains during growth based on nonlinear rheology

摘要

This work investigated the chain structure and large amplitude oscillatory shear (LAOS) rheological properties of waxy maize starch (WMS) at different growth periods and established a motion model to clarify the evolution of starch chain structure. During the growth period of 20-25 days, the apparent viscosity and dynamic moduli for WMS paste decreased, along with a greater degree of nonlinearity. This could be correlated with an increasing branching degree of starch due to more short-branched chains generated during growth. With the growth period reaching 25 days, the apparent viscosity, dynamic moduli and zero-strain nonlinearity (Q(0)) for WMS increased and the b value deviated from 2 significantly, indicating obvious nonlinearity accompanied by a weak stress overshoot and shear-thickening. This could be explained by the growing length of branched chains and the rising content of B-3(-) and B-4-chains. Thus, this work demonstrate LAOS rheology can be used as a new and effective method to characterize the chain structural evolution of starch through monitoring the motion pattern of different starch chains under shear conditions.

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