33B-1 |
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A. M. ELSTON1, J. Lin2, and R. L. Rouseff1. (1) Citrus REC, Univ. of Florida, 700 Experiment Station Rd., PO Box 111563, Lake Alfred, FL 33850, (2) Firmenich, Inc., 250 Plainsboro Rd., Plainsboro, NJ 08536 Orange peel oil is a byproduct of orange juice production. Valencene is the major sesquiterpene and its concentration is traditionally used to determine the value of orange oil. Nootkatone is the major sesquiterpene in grapefruit oil and is used to determine oil value. Nootkatone is aroma active and a grapefruit character impact compound. Several patents cite Valencene as an important and desirable compound in orange flavor. However, a definitive examination of the aroma activity of Valencene has not been published to date. The objective was to establish if Valencene possesses aroma activity at the levels found in orange oil thus determining if its use as a causative marker of economic value can be justified. Multidimensional GC-GC/O/MS separates mixtures of complex volatiles using two chromatographic columns of widely differing polarity with the ability to send fractions from the first column to be separated on the second column. Volatiles are identified using retention indices, aroma description and mass fragmentation patterns. Neral, which elutes near Valencene on a polar column, possessed a citrusy/woody type aroma. Both compounds have similar odors and are easily confused. The citrusy/woody aroma peak was heartcut to a second more nonpolar chromatographic column and split between a mass spectrometer and an olfactory port. Aroma activity was only detected for neral and not Valencene. Identities of both compounds were confirmed by MS. The use of multidimensional instrumentation coupled with olfactometric and mass spectral capabilities allowed for the unambiguous determination of the aroma activity of Valencene and compounds which elute close to it. Valencene did not exhibit aroma activity. Aroma activity in the same retention region was due to neral. Thus the use of Valencene as a causative marker for good quality orange oil must be questioned. It may simply correlate with the increase in orange flavor quality with more mature fruit.
Session 33B, Citrus Products: General
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