Mixing is a critical operation in dough processing. Because mixing itself is a complex combination of rotational, shear and elongational deformations, it has always been extremely difficult to understand dough mixing on a mechanistic level. Apart from that, a quantitative relationship between the type of deformation in the mixing and the resulting dough properties is still lacking. This paper reviews our main findings in this field. We focused on the effects of well-defined flow regimes on dough properties to gain a mechanistic insight in dough processing and concluded that simple shear flow and elongational flow influenced material quite differently.
In elongational flow, the material was stretched and largely deformed favouring the break-up phenomenon. Simple shear flow caused rotation of protein patches, which promotes colloidal aggregation and local phase separation. High shear rates induced break-up of gluten domains and development of a network without having a severe effect on a molecular scale. The results outlined that it is not the mechanical energy input, but the type of deformation applied that is of crucial importance in dough processing. Dough was rather process tolerant upon simple shearing suggesting clear opportunities for making dough processing milder. Theses findings shed a new light on the concept of under, optimally and over-mixing, and open up interesting possibilities for innovative mixer designs.
