(E)-3-unsaturated volatile acids, alcohols, and aldehydes contribute to food odors, and they serve as a means of communication in their roles as pheromones. Until now, there has been no systematic study of their aroma properties and perception thresholds.

Andrea Buettner, Fraunhofer Institute for Process Engineering and Packaging, Freising, Germany, and colleagues characterized odors and odor thresholds for several homologous series of these compounds. They used NMR, GC, MS, and volunteer panelists who were trained to recognize and describe odorants using standard terminology.

Panelists described odors in the (E)-3-alkenal series as grassy (pentenal), soapy (heptenal), fatty (nonenal), and coriander-like (dodecenal). The short-chain compounds are found in cheese, olive oil, and yellow passion fruit, and the medium-chain compounds are present in red wine, pepper, various berries, and roasted chickpeas. The long-chain compounds are not observed in foods.

(E)-3-pentenal had the lowest median odor threshold, 3.03 ng/L. Differences in individual detection abilities were generally greatest for compounds with 8-, 9-, and 10-carbon chains. Panelist varied widely in their ability to detect (E)-3-alkenoic acids, which are found in soy sauce, rhubarb, and black tea.

• Structure–Odor Relationships of (E)-3-Alkenoic Acids, (E)-3-Alken-1-ols, and (E)-3-Alkenals,
  Katja Lorber, Andrea Buettner,
  J. Agric. Food Chem. 2015.
  DOI: 10.1021/acs.jafc.5b02169