Role of hydrogen peroxide produced by Baker's yeast on dough rheology

Baker's yeast, Saccharomyces cerevisiae, has a well-known effect on dough rheology during breadmaking. During a 3-hr fermentation, hydrogen peroxide (H2O2) produced by yeast (0.76%, fwb) increased from 1.09 to 2.32 mu mol/g of flour. The spread test, a measure of a dough's rheological properties, showed that yeast had an effect on dough rheology similar to that of H2O2, an oxidant that makes flour-water dough more elastic. In additional experiments (spread test and H2O2 measurement), glucose oxidase, an enzyme that produces H2O2 gave results similar to those with yeast. The fact that catalase, an enzyme that destroys H2O2, reversed the rheological effect of added H2O2 but did not reverse the effect of either yeast or glucose oxidase suggested that either wheat flour contains an inhibitor to catalase or H2O2 was not the active component. A series of experiments, including use of defatted flour, remixing, and mixing dough under nitrogen, all indicated that catalase was inhibited by peroxides in the lipid fraction of flour. These results also suggested that H2O2 is responsible for the effects of yeast and glucose oxidase on dough.