Submitted to: Flavour and Fragrance Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2003
Publication Date: 3/29/2004
Citation: Park, B-S., Lee, K-G., Takeoka, G.R. 2004. Comparison of three sample preparation methods on the recovery of volatiles from taheebo (Tabebuia impetiginosa Martius ex DC). Flavour and Fragrance Journal. Vol 19:287-292. Interpretive Summary: The isolation of odor-active volatiles from complex food matrices remains a challenge to flavor chemists involved in the identification and quantification of food odorants. Ideally, a sample preparation technique should have the following characteristics: (1) it should provide efficient recoveries of different classes of volatiles, (2) the conditions utilized should not alter the structure of the important flavor constituents, and (3) the extract of volatiles should not contain any non-volatile material such as lipids and carotenoids that would interfere with subsequent gas chromatographic analyses. This study compared three sample preparation methods on the recovery of volatiles from taheebo, a herb derived from the bark of various South and Central American Tabebuia species. This herb is of interest since we recently found that the antioxidant activity of taheebo volatiles was comparable to that of the well-known antioxidants, alpha-tocopherol and BHT. The solvent assisted flavor evaporation method (SAFE) and steam distillation under reduced pressure followed by continuous liquid-liquid extraction (DRP-LLE) method gave similar recoveries of volatiles though the SAFE method gave better recoveries of polar constituents such as 1,2-propanediol. The SAFE method allows a fast and careful isolation of volatiles from the solvent extracts of foods and may be recommended as the best overall method of sample preparation.
Technical Abstract: The volatile constituents of taheebo (the dried inner bark of Tabebuia impetiginosa Martius ex DC) were isolated by three methods: solvent assisted flavor evaporation (SAFE), steam distillation under reduced pressure followed by continuous liquid-liquid extraction (DRP-LLE), and high-flow dynamic headspace sampling (including closed loop stripping) (DHS). The extracts were analyzed qualitatively and quantitatively by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The masses of total volatile components recovered from 50 g of taheebo by SAFE, DRP-LLE, and DHS were 26.3+/-2.0, 19.4+/-1.0, and 1.2+/-0.2 mg, respectively. The major constituents isolated with the SAFE method were 4-methoxyphenol (121.65 ug/g), 4-methoxybenzyl alcohol (96.49 ug/g), 1,2-propanediol (92.95 ug/g) and 4-methoxybenzaldehyde (31.33 ug/g). The DRP-LLC method yielded 4-methoxybenzaldehyde (64.54 ug/g), 4-methoxyphenol (42.30 ug/g), 5-(2-propenyl)-1,2,3-trimethoxybenzene (elemicin; 41.22 ug/g), and 1-methoxy-4-(1E)-1-propenylbenzene (trans-anethole; 39.16 ug/g) as major volatiles while the main compounds recovered with the DHS method were 4-methoxybenzaldehyde (2.61 ug/g), 4-methoxyphenol (2.10 ug/g), 2-methyl-5-(1-methylethenyl)-2-cyclohexen-1-one (carvone; 1.71 ug/g) and 3,7-dimethyl-1,6-octadien-3-ol (linalool; 1.64 ug/g).