Wheat bread crumb, odorants

Table IV. Important Odorants (FD 32) of Wheat Bread Crumb Results of an Aroma Extract Dilution Analysis and Identification Experiments (Schieberle, P Grosch, W. in preparation)...

Taste and flavor of bread can be improved with optimal use of sourdough (Seibel and Briimmer, 1991). The flavor of sourdough wheat bread is richer and more aromatic than in wheat bread, a factor that can be attributed to the long fermentation time of sourdough (Briimmer and Lorenz, 1991). Studies on the influence of lactic acid bacteria on the aroma of wheat bread revealed a positive influence, particularly on the crumb aroma (Hansen and Hansen, 1996). The concentration of 2-phenylethanol, one of the most potent odorants of wheat bread crumb (Grosch and Schieberle,... 

The composition of the volatile fraction of bread depends on the bread ingredients, the conditions of dough fermentation and the baking process. This fraction contributes significantly to the desirable flavors of the crust and the crumb. For this reason, the volatile fraction of different bread types has been studied by several authors. Within the more than 280 compounds that have been identified in the volatile fraction of wheat bread, only a relative small number are responsible for the different notes in the aroma profiles of the crust and the crumb. These compounds can be considered as character impact compounds. Approaches to find out the relevant aroma compounds in bread flavors using model systems and the odor unit concept are emphasized in this review. A new technique denominated "aroma extract dilution analysis" was developed based on the odor unit concept and GC-effluent sniffing. It allows the assessment of the relative importance of the aroma compounds of an extract. The application of this technique to extracts of the crust of both wheat and rye breads and to the crumb of wheat bread is discussed. 

The aroma extract dilution analysis was applied to extracts obtained from the crumb of wheat bread. Twenty nine odorants were detected and the flavor compounds responsible for the odor notes identified (Schieberle, P. Grosch, W. in preparation). The 12 aroma compounds having the highest FD-factors are presented in Table IV. 

Although more than 280 compounds have been identified in the volatile fiction of wheat bread, only a small number is responsible for the flavor notes in the crust and the crumb. Schieberle and Grosch (73) used aroma extract dilution analysis (AEDA) to select 32 odorants in wheat. Among the odorants, 2-acetyl-pyrroline (roasly, bread crust-like) was the most potent aroma, followed by E-2-nonenal (green, tallowy), 3-methylbutanal (malty, nutty), diacetyl (buttery) and Z-2-nonenal (green, fiitty). 

Gassenmeier, K. and Schieberle, P. 1995. Potent aromatic compounds in the crumb of wheat bread (French-type). Influence of preferments and studies on the key odorants during dough processing. 

Two compounds that create the characteristic odor notes in the pleasant aroma of wheat bread crust have been identified as the popcomUke 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine (51). The aroma of the bread crumb portion is principally due to lipid-derived unsaturated aldehydes such as E)-2-nonenal and ( , )-2,4-decadienal, which create stale aromas at high levels. The malty notes that predominate in yeast and sourdough breads are attributed to 2-and 3-methylbutanal and Furaneol (51,55). 

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