FORMATION OF VOLATILE FLAVOR COMPOUNDS IN GREEN BEANS FROM LINOLEIC AND LINOLENIC ACIDS

Both green beans and seeds formed n-hexanol, n-hexanal and 1-octen-3-ol as the principal volatile compounds from U-14C-labeled linoleic acid but at proportionately different ratios. With U-14C-labeled linolenic acid, green beans developed mainly trans-2-hexanal, 1-penten-3-ol, 3-penten-1-ol, trans-2-hexenol and cis-3-hexenol, while seeds produced largely 1-penten-3-ol and 3-penten-3-ol with a small amount of trans-2-hexenal. Green beans showed the highest lipoxygenase activity of the several fruits and vegetables compared. Though alcohol oxidoreductase was relatively low, rapid reduction of aldehydes/ketones to alcohols was found in green beans. Green bean lipoxygenase was inhibited by cyanide and a small fraction appeared to be quite heat stable, compared to alcohol oxidoreductase which was much more unstable. The optimal activity of green bean lipoxygenase was found to be at pH 5.8.