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Comparison of gluten viscoelasticity components with traditional dough and baking tests

Chompoorat, Pavalee
Quantitate analysis of viscoelastic properties of gluten were done by using mechanical analogs, i.e., spring, spring and dashpot arranged in parallel, and dashpot, to describe the elasticity, delayed elasticity and viscous response. The regressed parameters from nine sets of samples were correlated with dough and bread quality. A surfactant (DATEM) decreased elastic deformation (J0) and increase resistance to flow (no) of gluten. While, more deformable gluten (increase in instantaneous elastic compliance J0 and delayed elastic compliance J1) was obtained by treatments of oxidation, reduction of disulfide bonds, and disruption of hydrogen bonds with treatments of ascorbic acid, dithiothreitol, and urea, respectively. The results proved that the contributions of non-covalent bonds which are hydrogen bonds and hydrophobic interactions are as important as disulfide bonds to gluten structure. It also suggested the importance of stable protein aggregation and interactions via a surfactant involving hydrophilic and hydrophobic domains. Deformation (J0 and Jr0) of gluten started to decrease after heating at 45 degrees C, suggesting that non-covalent bonds were affected. After heating up to 65 degrees C, the resistance to flow and recoverability of gluten increased, suggesting that gluten agglomeration and formation of covalent bonds was induced by heating at 65 degrees C. Commercial gluten showed different effects when used in flour substitutions. Gluten B with more acidity (pH=4.2 vs 5.2 or 5.5) deformed gluten structure more than gliadin (a plasticizer). After substituting gluten GB, GC, and gliadin, the resistance to flow of gluten decreased and J0 and J1 increased indicating an increase in gluten deformation. This suggests that no new disulfide bonds were formed. We speculate that native disulfide bonds were diluted by increasing the concentrations of gluten and only hydrophobic interactions and hydrogen bonds were formed by GB, GC, and gliadin. Gluten strength and deformability were the main contributors of the variance in breeder line samples of crop years 2008 to 2011. Gluten recoverability and flour protein also contributed to the variance as second and distant third contributors and were independent of strength and deformability. The viscous coefficients were positively correlated with dough mixing properties.