Identification and quantification of potent odorants formed by toasting of wheat bread

Slices of wheat bread were toasted until a distinct intensity of brown colour was attained. Potent odorants formed were evaluated by aroma extract dilution analysis and gas chromatography/olfactometry of headspace samples. Compounds showing high dilution factors were quantified, and their aroma activity values (OAV, ratio of concentration to odour threshold) were calculated on the basis of their odour thresholds in starch. The roasty smelling 2-acetyl-1-pyrroline (I) showed the highest OAV followed by (E)-2-nonenal (II), 3-methylbutyric acid (III), 4-hydroxy-2,5-dimethyl-3 (2H)-furanone (IV), methional (V) and 2,3-butanedione. Formation of nine odorants (I to V among others) was measured in relation to the intensity of the brown colour. It was found that, at the beginning of toasting, (I) increased more rapidly in the bread slices than (IV) which was mainly produced at medium browning.