The effects of yeast metabolites on the rheological behaviour of the dough matrix in fermented wheat flour dough

In this study, the rheological impact of the main yeast metabolites besides CO2 was investigated. By adding these metabolites to unfermented dough at the concentrations observed in fermented dough, the associated rheological changes could be examined with fundamental rheological techniques (oscillatory and uniaxial extensional tests). Glycerol had a softening effect on dough similar to water. Ethanol altered the configuration of the gluten network, resulting in a decrease in the dough's extensional viscosity and extensibility. The stiffness and extensional viscosity were also reduced by succinic acid and glutathione. Subsequently, the impact of these metabolites on the rheology of dough was also investigated in situ by studying the rheological changes in the dough matrix following fermentation. Compared to unfermented dough, the fermented dough matrix exhibited reduced extensibility and a lower maximum extensional viscosity. The storage modulus also decreased, but only at low frequencies. The observed changes can partially be accounted for by the yeast metabolites, yet it is clear that the rheological behaviour of the fermented dough matrix does not merely resemble a superposition of the rheological changes associated with the main yeast metabolites. The differences may reflect the time-dependent accumulation of metabolites in the expanding gluten network during fermentation.