GAS-CHROMATOGRAPHY OLFACTORY ANALYSIS OF LYCHEE (LITCHI-CHINESIS SONN.)

Volatile compounds from lychee (Litchi chinesis Sonn.), a tropical fru it native to China, were extracted using both Freon 113 and ethyl acet ate solvents. The odor-active compounds present in the fruit were isol ated and characterized using gas chromatography/olfactory (GC/O), chro matography, and mass spectrometry. Authentic standards were used to de termine mass spectral, retention index, and odor match. GC/O analysis detected at least 60 odor-active volatiles in the fruit extract. More odor-active volatiles were detected in the ethyl acetate extract than in the nonpolar Freon extract. Among the compounds that had significan t odor activity, geraniol, guaiacol, vanillin, 2-acetyl-2-thiazoline, 2-phenylethanol, unknown (58), (Z)-2-nonenal, beta-damascenone, 1-octe n-3-ol, Furaneol, and linalool were found to be the most odor-active. On the basis of their calculated odor activity values (OAV), isobutyl acetate, guaiacol, cis-rose oxide, 2-acetyl-2-thiazoline, beta-damasce none, Furaneol, linalool, (E)-2-nonenal, geraniol, and isovaleric acid were determined to significantly contribute to the aroma of this frui t. GC/O analysis confirmed that 2-phenylethanol was probably responsib le for the floral character and that the citrus-fruity aroma is due to the presence of many odor-active terpenes, particularly geraniol. Alt hough cis-rose oxide was only 30% as active in GC/O as the most potent odor, its high OAV indicates its importance to the character of lyche e odor. An unknown sesquiterpene-like compound (58), with a lychee-lik e odor characteristic of the fresh fruit, was identified by GC/O as be ing a highly odor potent compound. Taken together, the aroma of lychee was determined to be due to the interaction between compounds with fl oral, nutty, citrus, and fruity aromas.