Volatile Components of Tamarind (Tamarindus indica L.) Grown in Cuba

Journal of Essential Oil Research: JEOR, Jul/Aug 2004 by Pino, Jorge A, Marbot, Rolando, Vazquez, Carlos

Abstract

Volatile components of tamarind fruits grown in Cuba were isolated by simultaneous steam distillation/solvent extraction. The fruit pulp had approximately 3 mg/kg of total volatile compounds. Eighty-one constituents were identified, from which 2-phenylacetaldehyde, 2-furfural and hexadecanoic acid were the major compounds.

Key Word Index

Tamarindus indica, Leguminosae, tamarind, fruit volatiles, 2-phenylacetaldehyde, 2-furfural, hexadecanoic acid.

Plant Name

Tamarindus indica L. (Leguminosae), tamarind.

Source

Plant material was collected from trees growing in the National Botanic Garden, near Havana.

Plant Part

Fully grown, mature fruits were collected. They were stored at room temperature and processed within one week of harvest.

Previous Work

The tamarind (Tamarindus indica L.), native to the tropical Africa, is distributed throughout practically all the tropical countries of the world. The fruits are flattish, bean-like and irregularly shaped pads. As they mature, the pods fill out and the juicy, acidulous pulp turns brown or reddish-brown. The most outstanding characteristic of the tamarind fruit is that it is the most acidic of all fruits, with a total acidity range varying from 12-24% as tartaric acid; however, it also has a high total sugar content, varying from 21-31% (1). The overall aroma of tamarind is characterized by its warm, citrus-like notes and some roasted undertones. The chemical composition of the volatiles of tamarind grown in other regions has been the subject of several studies (2-6).

Present Work

Fresh fruit pulp (400 g) from ripe fruits was blended with distilled water, adjusted to pH 7, and continuously steam distilled-diethyl ether extracted in a Likens-Nickerson apparatus for 90 min. The extract was dried over anhydrous sodium sulfate, concentrated using a Kuderna-Danish concentrator and finally, reduced to a volume of about 0.2 mL under a gentle stream of nitrogen.

The extract was analyzed by GC using a Hewlett-Packard 6890 gas Chromatograph equipped with a flame ionization detector (FID). The separations were performed using a SPB-5 column (30 m � 0.25 mm, 0.25 �m film thickness) with an oven temperature program of 60�C (2 min), 4�C/min to 250�C (20 min). The carrier gas was helium with a flow-rate of 1 mL/min. The temperature of the injector and detector was 250�C. The injection was made in the split mode (1:10 ratio). Linear retention indices were calculated against those of n-paraffins (7). These conditions were used for quantitative analysis, by the internal standard method.

GC/MS analyses were performed with a Hewlett-Packard series 6890 gas Chromatograph equipped with an HP-5973 mass-selective detector. The Chromatographic conditions were the same as those described for GC-FID. The detector operated in electron impact mode (70 eV) at 230�C. Detection was performed in the scan mode between 30 and 400 amu.

Component identification was carried out by comparing the relative retention indices and mass spectra of reference compounds. Mass spectra of published data were also compared (8,9).

The yield of total volatiles, estimated by the addition of a measured amount of methyl undecanoate (internal standard) to the sample prior to extraction, was near to 3 mg/kg fruit pulp. A complete list of the compounds identified, in the order of elution from SPB-5 column, is given in Table I. Eighty-one volatile compounds were identified from which aromatic and furan derivatives, and fatty acids were dominant. The major constituents were 2-phenylacetaldehyde (25.4% of the total volatiles), 2-furfural (20.7%) and hexadecanoic acid (18.1%). The odor character of 2-phenylacetaldehyde is fruity and honey-like. The 2-furfural has a sweet character and caramel-like flavor. This compound, together with 2-acetylfuran and 5-methylfurfural, is usually formed as a degradation product of ascorbic acid and sugars. Nevertheless, the concentrate was found, on appropriate redilution with water, to possess the characteristic fresh tamarind aroma. The citrus note of tamarind may be due to the presence of limonene. These constituents appear to contribute significantly to the overall tamarind aroma.

References

1. F.W. Martin, C.W. Campbell and R.M. Puberte, Perennial Edible Fruits of the Tropics: An Inventory. USDA, Agric. Res. Service, Washington D.C. (1987).

2. P. L. Lee, G. Swords and G.L.K. Hunter, Volatile constituents of tamarind (Tamarindus indica L). J. Agric. Food Chem., 23, 1195-1199 (1975).

3. A. Askar, S.E. EI-Nemr and H. Siliha, Aroma constituents of Egyptian tamarind pulp. Deut. Lebensmut.-Rundsch., 83, 108-110 (1987).

4. Y.-G. Zhang, C.-T. ho and A.L. Khurana, Volatile flavor components of tamarind (Tamarindus indica). J. Essent. oil Res.,2, 197-198(1990).

5. L. Sagrero, J.P. Bartley and A. Provis-Schwede, Supercritical fluid extraction of the volatile constituents from tamarind (Tamarindus indica L). J. Essent. oil Res., 6, 547-548 (1994).

6. K.C. Wong, C.P. Tan, C.H. Chow and S.G. Chee, Volatile constituents of the fruit of Tamarindus indica L. J.Essent. oil Res., 10, 219-221 (1998).