A team of scientists at the Technische Universität München in Germany has identified the key compounds that give soft pretzels their distinctive scent.
Soft pretzels have a uniform brown crust color and elicit a characteristic aroma that is clearly different from those of other small types of bread. Image credit: Kerstin Riemer.
The characteristic taste, texture and smell of pretzels results in part from lye treatment of the pretzel dough, as well as from the coarse salt sprinkled on top.
Like other foods, pretzels emit dozens of volatile compounds, but it can be difficult to determine which of these actually interact with odor receptors in the nose to trigger an aroma perception in the brain.
Technische Universität München researchers Sebastian Schoenauer and Peter Schieberle wanted to identify the volatile compounds in soft pretzels that make their aroma different from that of the other baked goods.
Using trained sensory panelists, the scientists first determined that the brown crust, rather than the white crumb, of soft pretzels elicited the unique aroma.
They then extracted volatile compounds from the pretzel crust and separated them by gas chromatography.
With their noses, they determined which ones had an odor, and identified them with mass spectrometry.
Additional experiments with the panelists revealed that 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like odor) and 2-acetyl-1-pyrroline (roasty, popcorn-like smell) were the key contributors to the pretzel aroma profile.
The team then created a good approximation of the pretzel smell in the lab by combining the top six odor components.
Although some of the same odorants were present in other baked goods, the overall amounts and ratios between components varied.
The team’s work appears in the Journal of Agricultural and Food Chemistry.
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Sebastian Schoenauer & Peter Schieberle. 2019. Characterization of the Key Aroma Compounds in the Crust of Soft Pretzels by Application of the Sensomics Concept. J. Agric. Food Chem 67 (25): 7110-7119; doi: 10.1021/acs.jafc.9b02601