Trans-4,5-Epoxy-(E)-2-decenal explained

trans-4,5-Epoxy-(E)-2-decenal (E2D)is an oxygenated α,β-unsaturated aldehyde found in mammalian blood that gives blood its characteristic metallic odor. It is used by predators to locate blood or prey.^[1] trans-4,5-Epoxy-(E)-2-decenal is almost certainly found in all mammals.^[2] Humans can smell it at a concentration of 1.5 pg/L in air,^[3] at 15 ng/L in water and 1.3μg/L in oil.^[4] It was permitted as a food flavouring in the EU until it was prohibited on 11 July 2017^[5] on the grounds of possible genotoxicity, as observed from rat livers.^[6]

It can be formed during baking fats that contain linoleic acid. 13-Hydroperoxy-9,11-octadecadienoic acid and 9-hydroperoxy-10,12-octadecadienoic acid are intermediates in the process.^[7] The aldehyde also forms in cooked beef when it sits in the refrigerator for too long contributing to a stale smell.^[8] It is also an important part of the smell of raw and cooked mutton.^[9]

Humans are more sensitive to the smell of trans-4,5-Epoxy-(E)-2-decenal than mice.^[10]

Notes and References

1. Web site: Odor that smells like blood: Single component powerful trigger for large carnivores. 11 November 2014. Physorg. 11 November 2014.
2. Arshamian . Artin . Laska . Matthias . Gordon . Amy R. . Norberg . Matilda . Lahger . Christian . Porada . Danja K. . Jelvez Serra . Nadia . Johansson . Emilia . Schaefer . Martin . Amundin . Mats . Melin . Harald . Olsson . Andreas . Olsson . Mats J. . Stensmyr . Marcus . Lundström . Johan N. . A mammalian blood odor component serves as an approach-avoidance cue across phylum border - from flies to humans . Scientific Reports . 20 October 2017 . 7 . 1 . 10.1038/s41598-017-13361-9. 5651850 .
3. Lin. Jianming. Laurent B. Fay . Dieter H. Welti . Imre Blank . 2001. Quantification of key odorants formed by autoxidation of arachidonic acid using isotope dilution assay. Lipids. 36. 7. 749–756. 0024-4201. 10.1007/s11745-001-0781-x. 11521974. 3979031.
4. Lin. Jianming. Laurent B. Fay . Dieter H. Welti . Imre Blank . 1999. Synthesis of trans-4,5-epoxy-(E)-2-decenal and its deuterated analog used for the development of a sensitive and selective quantification method based on isotope dilution assay with negative chemical ionization. Lipids. 34. 10. 1117–1126. 0024-4201. 10.1007/s11745-999-0463-8. 10580339. 4054911.
5. Web site: COMMISSION REGULATION (EU) 2017/1250 of 11 July 2017 amending Annex I to Regulation (EC) No 1334/2008 of the European Parliament and of the Council as regards removal from the Union list of the flavouring substance 4,5-epoxydec-2(trans)-enal. 11 July 2017. Official Journal of the European Union.
6. EFSA CEF Panel . Scientific Opinion on Flavouring Group Evaluation 226 Revision 1 (FGE.226Rev1): consideration of genotoxicity data on one α,β-unsaturated aldehyde from chemical subgroup 1.1.1(b) of FGE.19 . EFSA Journal . 2017 . 15 . 5 . 4847–4871 . 10.2903/j.efsa.2017.4847 . 32625501 . 7010128 .
7. Gassenmeier. Klaus. Peter Schieberle. 1994. Formation of the intense flavor compound trans-4,5-epoxy-(E)-2-decenal in thermally treated fats. Journal of the American Oil Chemists' Society. 71. 12. 1315–1319. 0003-021X. 10.1007/BF02541347. 85079936.
8. Konopka. Ute Christine. Werner Grosch. 1991. Potent odorants causing the warmed-over flavour in boiled beef. Zeitschrift für Lebensmittel-Untersuchung und -Forschung. 193. 2. 123–125. 0044-3026. 10.1007/BF01193360. 83249703.
9. Book: Rota, Valerie. Peter Schieberle. 2005. 920. 73–83. 1947-5918. 10.1021/bk-2005-0920.ch006. Changes in Key Odorants of Sheep Meat Induced by Cooking. Food Lipids. ACS Symposium Series. 0-8412-3896-0.
10. McGann . John P. . Poor human olfaction is a 19th-century myth . Science . 11 May 2017 . 356 . 6338 . eaam7263 . 10.1126/science.aam7263. 28495701 . 5512720 . free .