Mapping of Saccharomyces cerevisiae metabolites in fermenting wheat straight-dough reveals succinic acid as pH-determining factor

► The carbon metabolism of yeast was mapped during bread straight-dough fermentation. ► Succinic acid was observed to be the main organic acid produced in these experiments. ► The pH decrease in fermenting dough is mainly caused by succinic acid production. Fermenting yeast does not merely cause dough leavening, but also contributes to the bread aroma and might alter dough rheology. Here, the yeast carbon metabolism was mapped during bread straight-dough fermentation. The concentration of most metabolites changed quasi linearly as a function of fermentation time. Ethanol and carbon dioxide concentrations reached up to 60mmol/100g flour. Interestingly, high levels of glycerol (up to 10mmol/100g flour) and succinic acid (up to 1.6mmol/100g flour) were produced during dough fermentation. Further tests showed that, contrary to current belief, the pH decrease in fermenting dough is primarily caused by the production of succinic acid by the yeast instead of carbon dioxide dissolution or bacterial organic acids. Together, our results provide a comprehensive overview of metabolite production during dough fermentation and yield insight into the importance of some of these metabolites for dough properties.