BREAKDOWN OF THE FLAVOR COMPOUND 2(E)-HEXENAL IN DIFFERENT SOLVENTS

The influence of the solvents 20 per cent (v/v) aqueous ethanol (pH 3·5, Et) and triacetin (Tr) on the rate and on the products of the breaksown of 2(E)-hexenal at 38°C has been investigated. The rate constants (× 10-3h-1), which were determined for hexanal (7·65 Et, 8·04 Tr), 2(E)-hexenal (3·8 Et, 9·8 Tr), 3(Z)-hexenal (20·08 Et, 26·35 Tr) and some C7-aldehydes, indicated that 2(E)-hexenal was more stable in Et than in Tr. In Tr, autoxidation of 2(E)-hexenal to the corresponding acid was the major reaction and the minor product, butanoic acid, was the most important odour compound. In Et, the flavour potential of 2(E)-hexenal was lowered by the formation of 3-hydroxyhexanal and 3-ethoxyhexanal. Isomerisation of the 2(E)-double bond into 2(Z)-, 3(E)- and 3(Z)-double bonds also took place, affording among other compounds, 3(Z)-hexenal which, on the basis of its low odour threshold, predominated in the overall aroma. © 1990.