Potent odorants of the wheat bread crumb Differences to the crust and effect of a longer dough fermentation

Characterization of the crumb flavour of wheat bread by means of an aroma extract dilution analysis indicated diacetyl, methional, 1-octen-3-one, (Z)-and (E)-2-nonenal, (E,E)-2,4-decadienal and trans-4,5-epoxy-(E)-2-decenal as the most potent odorants. The epoxydecenal had the lowest odour threshold (1.5 pg/L, air) among the homologous series of trans-4,5-epoxy-(E)-2-alkenals C₇-C₁₁. Prolongation of the dough fermentation resulted in a change of the crumb flavour which was mainly due to an increase in the concentrations of 3-methylbutanol and 2-phenylethanol. Stable isotope dilution assays indicated that the concentrations of the "roasty" smelling flavour compounds 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine were 30-fold lower in the crumb than in the crust. (E)-2-Nonenal, which is present in the flour, increased strongly during the baking process.