Effect of commercial dried sourdoughs on structural characteristics of wheat bread

This study investigated the effect of the addition of three commercial dried sourdoughs containing different percentages of Saccharomyces cerevisiae (25-30%), on structural characteristics of wheat bread. Rheology, texture and physicochemical characteristics were assessed for both dough and final bread. Control samples were prepared using common dried bakery’s yeast (100% S. cerevisiae). The rheological parameters complex viscosity (η), linear viscoelastic region (LVR), storage and loss modulus (G’ and G’’) and angular tangent (tanδ) were evaluated on the doughs through rheological tests carried out both in rotational and oscillatory mode. Final breads were characterised for the texture profile (hardness, springiness, cohesiveness and resilience). Moisture content and pH were monitored during the process. The leavening agents (dried sourdoughs and bakery’s yeast) were characterized for the content of total lactic acid bacteria and total yeasts. Rheological analysis highlighted a pseudo-plastic behaviour for all the doughs with the elastic component prevalent on the viscous one (G’>G’’), without substantial differences among samples before proofing. After 3 h leavening, storage and loss moduli and complex viscosity were lower than control for all the sourdough samples. Microbial evaluation showed no vital lactic acid bacteria in the dried sourdough that, contrary to the other two, did not give acidification during leavening and produced a final bread with texture properties comparable to those of the control.