Hexenal

A C6 aldehyde carrying one double bond, found in foods in several isomeric forms including trans-2-hexenal and cis-3-hexenal. It lends green, fresh aromatic notes and turns up in numerous fruits and other foods and drinks, generated when plant lipoxygenases attack unsaturated fatty acids. Processors watch it as a marker of fresh flavour — and, when it climbs unexpectedly in stored foods, of oxidative change. Because its concentration responds quickly to tissue damage, heat, and storage conditions, it is a sensitive indicator in studies of fruit ripening, vegetable processing, and the flavour stability of minimally processed products.