Impact of process parameters on the specific volume of wholemeal wheat bread made using sourdough- and baker's yeast-based leavening strategies.

The final quality of wholemeal wheat bread is determined by the process parameter settings and leavening strategy. We hypothesise that the used leavening strategy may influence the optimal process parameter settings and, as such, the specific volume of the bread loaf. To analyse this interaction, bread was leavened with (i) a type 1 sourdough (SB), (ii) a type 1 sourdough combined with baker's yeast (YSB), or (iii) baker's yeast (YB). For each leavening strategy, the specific volume of bread, in response to variations in mixing time (4-10/4-14 min), water absorption (60-85 %), and proofing time (1-7/1-3 h), was analysed using an I-optimal response surface experimental design. Data modelling identified a substantially lower maximal specific volume of SB (2.13 mL/g), compared to YSB (3.30 mL/g) and YB (3.26 mL/g). The proofing time and water absorption mostly influenced the specific volume of the SB and YSB, respectively. However, the mixing and proofing times mainly affected the specific volume of YB. The type 1 sourdough reduced the mixing time and water absorption required for an optimal specific volume of bread compared to baker's yeast. These results challenge the idea of yielding higher volumes upon using sourdough compared to baker's yeast and highlight the importance of optimisation of bread dough formulations and breadmaking processes.