Strategies towards improving the mechanical properties of rigid wheat gluten bioplastic

Strategies towards improving the mechanical properties of wheat gluten bioplastic. Wheat gluten is the storage protein of wheat. It consists of a mixture of gliadin and glutenin proteins and is found together with starch in the wheat endosperm. It is the most dominating wheat protein as up to 85% of all protein in wheat are gluten proteins. They are used in both food (pet food, breadmaking, meat replacements) and non-food applications (cosmetics, detergents, polymer products). Their use as a raw material for the production of bio-based material is fueled by their unique visco-elastic properties. Moreover, gluten proteins display very poor water solubility due to their low number of ionizable side chains. The objective of this research was to produce rigid, glassy gluten-based materials with mechanical properties approaching or outcompeting those of rigid plastics such as polystyrene. Hereto, linking the molecular changes in the gluten network with changes in its mechanical performance is the biggest challenge of this thesis. To produce rigid gluten-based materials, gluten was compressed at high temperatures. In the first part of this research, gluten was modified to remove all disulfide cross-links and create cross-link free (modified) gluten (MG). MG was molded and the resulting flexural strength of modified samples was significantly better than that of unmodified samples. In a second part, the gluten network was cross-linked with various cross-linkers with or without thermal activation. The physical properties of molded gluten material and its constituents (molded gliadin and glutenin) were analyzed and the influence on its mechanical properties was observed. It was shown that storage conditions have a big influence on the resulting mechanical properties. Moreover, a first attempt at rubber toughening the gluten matrix was made.status: publishe