Kindly check https://www.google.com/search?q=origin+of+2-hexenal+in+methyl+linoleate&client=ucweb-b&channel=sb

Also check http://www.thegoodscentscompany.com/data/rw1260021.html

Chinaza Godswill Awuchi irrelevant answers but thanks anyway.

Lorenzo - Thanks for the interesting question. To my knowledge aldehydes like 2-hexenal are the end-products of the oxidative degradation of unsaturated fatty acids and esters such as methyl linoleate. The first oxidation products are so-called hydroperoxides, which subsequently convert into the aldehydes. For more information please see the attached PhD thesis entitled "The quantification of carbonyl compounds produced from linoleic and linolenic acid hydroperoxides: thermal, metal ions and antioxidant effects". This should give you a good overview.