The flavor chemistry of rambutan (Nephelium lappaceum L.) and lychee (Litchi chinesis Sonn.).

摘要

Flavor-active compounds in rambutan (Nephelium lappaceum L.), a tropical fruit native to Southeast Asia, and lychee (Litchi chinesis Sonn.), a subtropical fruit native to China, were investigated. Both fruits belong in the Sapindaceae family. Odor-active compounds were isolated and characterized using gas chromatography-olfactory (GC/O), chromatography, and spectrometry. Authentic standards were used to determine mass spectral, retention index and odor match.; Of over a hundred volatiles detected by GC/MS in rambutan, twice as many polar volatiles were detected in the ethyl acetate extract as in the non-polar Freon extract. GC/O analysis also detected more odor-active compounds in the polar extracts. The twenty most potent odorants detected by GC/O included {dollar}beta{dollar}-damascenone, (E)-4/5-epoxy-(E)-2-decenal, vanillin, (E)-2-nonenal, phenylacetic acid, cinnamic acid, unknown (24), ethyl-2-methylbutyrate, and {dollar}delta{dollar}-decalactone. Based on calculated odor activity values (OAV), {dollar}beta{dollar}-damascenone, ethyl-2-methylbutyrate, 2,6-nonadienal, (E)-2-nonenal, and nonanal were determined to be the main contributors to the fruit aroma. (E)-4,5-epoxy-(E)-2-decenal was reported for the first time in a fresh fruit or vegetable.; GC/O analysis detected over 60 odor-active volatiles in lychee. Compounds with significant odor potency included, geraniol, guaiacol, vanillin, 2-acetyl-2-thiazoline, 2-phenylethanol, unknown (58), (Z)-2-nonenal, {dollar}beta{dollar}-damascenone, 1-octen-3-ol, Furaneol, and linalool. On the basis of OAV, isobutyl acetate, guaiacol, cis-rose oxide, 2-acetyl-2-thiazoline, {dollar}beta{dollar}-damascenone, Furaneol, linalool, (E)-2-nonenal, and geraniol were determined to significantly contribute to the lychee aroma. Although cis-rose oxide was only 30% as active in GC/O as the most potent odor, its high OAV indicated its importance to the character of lychee flavor. An unknown sesquiterpene-like compound (58), with a lychee-like odor characteristic of the fresh fruit, was identified by GC/O as being highly odor potent.; Similarities in the aroma chemistry of lychee and Gewurztraminer variety wines were studied. Twelve common odor-active compounds were identified in samples of fresh and canned lychee and Gewurztraminer wine, of which cis-rose oxide had the highest OAV in all three products. This indicated its importance to the aroma of both fruit and wine, and suggested cis-rose oxide being responsible for the lychee aroma perceived in Gewurztraminer wines. Using headspace SPME, selected aroma compounds contributing to lychee-aroma in Gewurztraminer-type wines were analyzed. Distinct differences in cis-rose oxide were seen in Gewurztraminers produced in New York state and the Alsace region in France, suggesting differences in viticultural and enological practices between regions.