Bread odorant, headspace

In an headspace extract of fresh rye bread crust, 3-methylbutanal, (E)-2-nonenal and methional showed the highest FD-factors (Table 4), while 2-acetyl-1-pyrroline, the key odorant of wheat bread crust (cf. Table 3), did not significantly contribute to the rye (rust flavor. Quantitative measurements established [45, 55] that especially the higher odor activity (cf. 3, this chapter) of the boiled potato-like smelling methional in the rye bread crust in combination with the much lower odor activity of the roasty-smelling 2-acetyl-l-pyrroline mainly contribute to the overall flavor differences in rye and wheat bread crusts. 

Odorants showing high FD-factors in a headspace extract of fresh rye bread crust [P. Schieberle and W. Grosch, unpublished results] ... 

The first comprehensive investigation of the volatiles of wheat bread was carried out by Mulders et al. (11. 16-18). After a qualitative analysis (16-18) which led to the identification of 90 compounds, the authors attempted to get an insight into the sensory relevance of the major components which were found in the headspace extract of white bread. A mixture of the main compounds identified was prepared in water to match the gas chromatogram obtained from the bread sample (11,). The odor of the synthetic mixture resembled that of the fermented dough but not that of wheat bread. 

Since in particular the cracker-like crust odor note was lacking in the synthetic mixture, it was concluded that the character impact compound for this odor note occurs in a concentration in the bread too low to be detected by headspace analysis. Later on the basis of its aroma quality and its very low odor threshold of 0.04 ppb (water), Mulders et al. (19) proposed 2-[(methyldithio)methyl] furan (4 in Figure 1) as the compound which should be responsible for the "golden brown" crust aroma of white bread. 

Fig. 5.4. Headspace analysis of aroma substances of white-bread crust, a Capillary gas chromatogram (the arrows mark the positions of the odorants), b FD chromatogram. Odorants 1 methylpropanal, 2 diacetyl, 3 3-methylbutanal, 4 2,3-pentanedione, 5 butyric acid, 6 2-acetyl-1-pyrroline, 7 l-octen-3-one, 8 2-ethyl-3,5-dimethylpyrazine, 9 (E)-2-nonenal (according to Schieberle and Grosch, 1992)...

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