Characterization of the Key Aroma Compounds in the Crust of Soft Pretzels by Application of the Sensomics Concept

Soft pretzels show a uniform brown crust color and elicit a characteristic aroma that is clearly different from those of other small types of bread. Data on the odorants responsible for this unique aroma are scarcely available. Application of aroma extract dilution analysis (AEDA) on an extract (distillate) obtained from the crust of freshly baked soft pretzels followed by identification experiments revealed 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF, caramel-like) and 2-acetyl-1-pyrroline (2-ACPY; roasty, popcorn-like), which had the highest flavor dilution (FD) factors among the 28 odor-active compounds identified. Quantitation of all 28 aroma compounds by stable isotope dilution assays (SIDA) and calculation of odor activity values (OAV) confirmed 2-ACPY, 4-HDF, and phenylacetic acid as key contributors to the pretzel aroma profile. Compared with other pastry crusts, in particular, the low odor activities of the Strecker aldehydes 2-and 3-methylbutanal, the lipid degradation product (E)-2-nonenal, and the lack of pyrazines were elucidated as the main reasons for the different aroma profile of pretzel crust. An aroma recombinate, which is among the first established for the crusts of breads and pastries, clearly mimicked the overall odor of the pretzel crust, in particular when a solution in ethanol was sprayed in the ambient air.