It is well-known that especially sulfur-containing odorants have a huge impact on the flavor of Alliaceae, e.g., onions and garlic. Degradation of the corresponding precursors lead to a variety of important aroma-active compounds and can occur either by the influence of enzymes or of temperature during heat-processing or of a combination of both. Furthermore, also the type of heat-treatment, e.g., cooking or deep-frying, plays an important role for the generation of a specific onion flavor. Based on literature knowledge, up to now, a few odorants have only been tentatively identified using mass spectrometry, but a detailed confirmation of the molecule structure is still missing. Therefore, the aim of the actual study was the characterization of the key odorants of cooked and deep-fried onions using the sensomics approach. Besides, the lecture will emphasis the importance of combining sensorial and instrumental-analytical techniques (GC/GC-MS using chiral stationary phases) to achieve a proper structural elucidation. Thereby, the significance of chiral odorants identified in cooked onions will be highlighted. The data obtained from cooked and deep-fried onions will be compared and discussed on a molecular level based on the fact that in deep-fried onions predominantly alkyl sulfides contribute to the characteristic aroma, while in the smell of cooked onions, cyclic sulfur compounds and thiols were the predominant odorants. Quantitative data of these chiral odorants in several Alliaceae, e.g., red onions, leek, shallots, chives, and spring onions, will be compared. Finally, the different sensory properties, ranging from cooked onion-like, via meat-broth-like to fruity odor impressions of the enantiomeric aroma-active molecules will be presented.

Flavor chemistry of heat-processed onions: Chiral aroma-active compounds can make the difference

2019 Spring National Meeting

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