Evolution of the aroma volatiles of pear fruits supplemented with fatty acid metabolic precursors.

To examine the biochemical metabolism of aroma volatiles derived from fatty acids, pear fruits were incubated in vitro with metabolic precursors of these compounds. Aroma volatiles, especially esters, were significantly increased, both qualitatively and quantitatively, in pear fruits fed on fatty acid metabolic precursors. Cultivars having different flavor characteristics had distinctly different aroma volatile metabolisms. More esters were formed in fruity-flavored "Nanguoli" fruits than in green-flavored "Dangshansuli" fruits fed on the same quantities of linoleic acid and linolenic acid. Hexanal and hexanol were more efficient metabolic intermediates for volatile synthesis than linoleic acid and linolenic acid. Hexyl esters were the predominant esters produced by pear fruits fed on hexanol, and their contents in "Dangshansuli" fruits were higher than in "Nanguoli" fruits. Hexyl esters and hexanoate esters were the primary esters produced in pear fruits fed on hexanal, however the content of hexyl ester in "Dangshansuli" was approximately three times that in "Nanguoli". The higher contents of hexyl esters in "Dangshansuli" may have resulted from a higher level of hexanol derived from hexanal. In conclusion, the synthesis of aroma volatiles was largely dependent on the metabolic precursors presented.