Mechanistic insights into the impact of acetic acid, lactic acid, and succinic acid on the dough rheology, the breadmaking process, and the specific volume of wholemeal sourdough-type bread

Lactic acid bacteria and yeasts produce organic acids, amongst other metabolites, during sourdough production and breadmaking. The resulting acidification is a crucial aspect of sourdough-type breadmaking. This study aimed to gain mechanistic insights into the impact of the primary organic acids, i.e. acetic acid, lactic acid, and succinic acid on the breadmaking process, the specific volume of wholemeal bread, and underlying dough rheological parameters. First, the interplay between the type of organic acid, the acidification level (dough pH of 4.5, 5.0, and 5.5), mixing time, and water absorption and their relation to specific bread volume was studied. Data analysis and modelling showed an increase of up to 22% in the predicted maximal specific volume of wholemeal bread when succinic acid (3.3 f 0.2 mL/g; pH = 4.5), lactic acid (3.1 f 0.2 mL/g; pH = 4.5), or acetic acid (3.0 f 0.2 mL/g; pH = 5.5) was added, compared to a control wholemeal bread (2.7 f 0.2 mL/g). This increase was only obtained when optimal process parameter settings were used because the robustness of the system decreased upon acidification. Insights into how the organic acids impacted the dough network were obtained by assessing the fundamental rheological properties of the bread dough. The increased extensional viscosity observed in acidified dough revealed more starch-starch, starch-gluten, and gluten-gluten interactions than in the unacidified control dough. Overall, this study highlights that acid addition can increase the specific volume of wholemeal bread and stresses the need for process optimisation. Moreover, the results suggest unique interactions of each acid type in the dough matrix. These results contribute to developing high-quality wholemeal sourdough-type bread by steering the acidification during sourdough production.