Résumé
Wheat grain structure appears heterogeneous composed of a number of tissues displaying distinct biochemical composition and mechanical properties. Grain milling has for aim to recover the starchy endosperm, which contains starch and the storage proteins able to form gluten, into flours or semolina from the outer layers. This separation is traditionally monitored through ash content measurement but do not allow strict separation. These last years, we developed biochemical markers, but also identify specific spectral signatures of each of the grain tissues to help determine their proportion in the different fractions obtained after milling or debranning. As we found differences in fractionation behavior between soft and hard cultivars carrying respectively wild-type genes encoding Puroindolines (PIN) A and B or a mutation in one of these genes, we analyzed near-isogenic lines differing only by a mutation in PINB. This allowed us to clearly distinguish the respective effect of genetic or environmental factors in wheat grain mechanical behavior. Taking into account what we know about the molecular and structural organization of the starchy endosperm, we developed a numerical model of the grain rupture which appeared to correctly mimic the experimental values obtained from mechanical rupture test at the scale of the starchy endosperm.