Effect of simple shear on the physical properties of glutenin macro polymer (GMP)

Gluten plays a key role in determining the end-use quality of wheat flour. The important role of the highly aggregated fraction of gluten, glutenin macropolymer (GMP), in dough properties opens up new possibilities for revealing underlying mechanisms related to dough processing. Using a new shear cell and advanced methodology to study the GMP, we investigated the effect of simple shear on the physical properties of this fraction. Shear processing was compared with z-blade mixing, which involves both shear and elongational forces. Measurement of the amount of GMP and glutenin particle size distribution revealed large differences between simple shearing and z-blade mixing processes. In contrast to z-blade mixing, simple shearing at comparable levels of mechanical energy input, did not lead to a decrease in the wet weight of GMP or the size of glutenin particles. Confocal scanning laser microscopy of doughs revealed that shear processing produced a homogeneously distributed dough protein matrix, however, the GMP extracted from the sheared dough showed the presence of large clusters of particles. On the other hand, z-blade mixing led to disruption of these particles. Thus the type of deformation applied during dough processing is of crucial importance and in designing new equipment for dough processing the principles of different types of shear should be considered.