|Hexanal, 1-hexanal, n-hexanal, is also known as caproaldehyde or hexanaldehyde. It belongs to the class of organic compounds known as medium-chain aldehydes which have a chain length between 6 and 12 carbon atoms and therefore is considered a fatty aldehyde lipid molecule. Hexanal is a very hydrophobic molecule that is relatively neutral. It is a colorless clear liquid. It has a fresh green, fatty or grassy scent with a green, fatty, leafy or aldehydic taste. Hexanal exists in all eukaryotes, from yeast to humans. Different foods contain hexanal with the highest concentrations found in black walnuts, corns, and tea and with lower concentrations in common grapes, thornless blackberries, and tortilla. Hexanal has also been detected in palms, mentha (mint), wax gourds, grapes, and kiwis making hexanal a potential biomarker for the consumption of these foods. Hexanal has been used to increase post-harvest longevity and color of certain fruits ( https://doi.org/10.1016/B978-0-12-809807-3.00009-3). Hexanal was also detected in humans breastmilk samples. Among mediators of oxidative stress, highly reactive secondary aldehydic lipid peroxidation products can initiate the processes of spontaneous mutagenesis and carcinogenesis and can also act as a growth-regulating factors and signaling molecules. In specimens obtained from adult patients with brain astrocytomas, lower levels of n-hexanal, together with higher levels of 2-hydroxyhexanal and 4-hydroxynonena, are associated with poorer patient prognosis (PMID: 17487452). Hexanal has also been identified as a uremic toxin according to the European Uremic Toxin Working Group because its concentrations in uremic patients were found to exceed the normal general population concentrations (PMID: 22626821). Hexanal is a volatile compound that has been associated with the development of undesirable flavours and has been proposed as a potential marker of milk quality. Hexanal, a major breakdown product of linoleic acid (LA, n ‚Äì 6, an polyunsaturated fatty acid, PUFA) oxidation, has been used to follow the course of lipid oxidation and off-flavour development in foods. A "cardboard-like" off-flavour is frequently associated with dehydrated milk products such as baby formulae and was correlated with the hexanal concentration (https://doi.org/10.1016/j.foodchem.2007.08.042).