Resilience study of wheat protein networks with large amplitude oscillatory shear rheology
Monika C. Wehrli, Semihan Ini, Mario Jekle, Tim Kratky, Thomas Becker
Abstract
This study investigates the effect of standard laboratory production steps on the network properties of vital gluten. Gluten experiences high mechanical input during production from wheat dough and subsequent processing, which influences the network characteristics. The production of vital gluten in laboratory scale ensures full control on all processing parameters and the possibility to obtain the protein using the mildest washing, drying and milling techniques. Large Amplitude Oscillatory Shear (LAOS) tests were performed on wheat dough, intermediate materials during gluten production and the final product vital gluten at frequencies of 1–15 rad/s and strains from 0.01 to 100%. The elastic and viscous behavior of the material are described by analyzing the fundamental response and the higher harmonics, based on Lissajous-Bowditch curves. The intra-cycle behavior revealed that vital gluten only exhibits network stiffening, whereas dough shows both strain stiffening and shear thinning effects. This suggests that starch induces the shear thinning effects in dough. Comparison of rehydrated and fresh gluten obtained from the same starting material reveals minor alteration of the protein secondary structures during the production process by means of Fourier-transform infrared spectroscopy (FTIR). A pronounced difference in water uptake accounts for modified rheological network properties.