Wheat endosperm as a cohesive granular material

We introduce a cohesive granular model of the wheat endosperm involving a discrete phase composed of starch granules, a continuous phase representing the protein matrix and pores. The cohesion of the texture is governed by adherence between starch and protein, reflecting the biochemical nature of the interface, and the protein content that controls the connectivity between starch granules. We present a detailed parametric study of the stiffness, yield strength and regimes of crack propagation under tensile loading. We then show that starch damage, as a descriptor of wheat hardness, scales with the relative toughness between the starch and the starch–protein interface. The toughness appears therefore to be the control parameter governing transition from ‘soft’ to ‘hard’ behavior. Interestingly, this parameter combines the starch–protein adherence with protein content, two major quantities often assumed to underly wheat hardness.