Impact of industrial dough processing on structure: A rheology, nuclear magnetic resonance, and electron microscopy study

Dough processing is an important factor determining the quality of bread. The most important mechanical steps in industrial dough processing are kneading, extrusion, and molding. In all of these processing steps, considerable changes in the structure and properties of the dough can occur. On a laboratory-scale level, these (structural) effects are well characterized but, so far, no systematic study has been performed at the level of a large-scale industrial dough processing line. The molecular and microstructural changes that can take place during industrial dough processing were studied with the help of nuclear magnetic resonance (NMR), fundamental rheology, and scanning electron microscopy (SEM). After the kneading step, the dough shows a well-developed gluten network with a homogeneous dispersion of starch particles (at optimum kneading time). After the extrusion step (a sheeting procedure), the structure of the dough becomes coarser and the dough gluten network is oriented and partially disrupted. This is accompanied with an increase in both rheological stress and water mobility. After molding, the network structure is restored and both the rheological stress and the mobility of water decrease. These findings provide a novel microstructurally-lead approach to make recommendations for optimization of industrial dough processing lines.