It is well accepted that sulfur compounds play the most important role for the aroma of onions. The degradation of sulfur containing precursors is the main reason for the specific aroma of differently heat-processed onions. But, up to now, many odorants have only been tentatively identified on the basis of mass spectrometry without any detailed structural confirmation. Thus, the aim of the present study was to characterize the key aroma compounds of cooked and of deep-fried onions by means of the molecular sensory science concept. The lecture will present structural elucidation of important odorants in cooked and deep-fried onions combining sensorial and analytical (gas chromatography-mass spectrometry using chiral stationary phases and nuclear magnetic resonance spectroscopy) tools. The emphasis will be on chiral compounds, which were only identified in cooked onions and which play an important role in the overall aroma. Further, the different sensory properties of the enantiomeric flavor compounds will be discussed. Finally, quantitative data of these chiral odorants in several Alliaceae will be compared. In conclusion, the results proved the different sensory impressions of cooked and deep-fried onions on a molecular level showing that especially chiral sulfur-containing odorants can only be unequivocally identified on the basis of sensory science in combination with modern analytical techniques.

Influence of chiral sulfur compounds on the aroma of heat-processed onions

248th National Meeting (2014)

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