Volatile Flavor Constituents of Karanda (Carissa carandas L.) Fruit

Journal of Essential Oil Research: JEOR, Sep/Oct 2004 by Pino, Jorge A, Marbot, Rolando, V�zquez, Carlos

Abstract

The volatile flavor constituents of karanda fruits (Carisssa camndas L.) growing in Cuba were analyzed by GC and GC/MS. One hundred and fifty compounds were identified in the aroma concentrate, of which isoamyl alcohol, isobutanol and [beta]-caryophyllene were found to be the major constituents.

Key Word Index

Carissa carandas, Apocynaceae, karanda, fruit volatiles, isoamyl alcohol, isobutanol, [beta]-caryophyllene.

Introduction

The karanda (Carissa carandas L.) is a strong, stragglygrowing shrub suitable for protective hedge plantings. It belongs to the Apocynaceae family and is probably native to India. The fruits are dark purple, seemingly black, when ripe. They vary from oval to round in shape and are about threequarters of an inch in diameter. The fruit makes an excellent acid jelly for serving with meats or fish. In India the green fruits are pickled (1).

The aromatic properties of this fruit led us to investigate its composition in order to determine the respective influence of the volatile constituents. To date the flavor of karanda fruit has not been the subject of a previous study.

Experimental

Materials and isolation of the volatile constituents: Samples of ripe fruits were collected from a National Botanic Garden in Havana in May 2002. A voucher specimen of the plant is deposited in the Herbarium of the National Botanic Garden. After addition of an internal standard (methyl undecanoate, 2 mg), pulp (200g) was blended with distilled water (600 mL), and simultaneously distilled and extracted for 60 min in a LikensNickerson microapparatus with 25 mL of diethyl ether (previously redistilled and checked as to purity). The volatile concentrate was dried over anhydrous sulfate and concentrated to 0.6 mL on a Kuderna-Danish evaporator with a 12-cm Vigreux column and then to 0.2 mL with a gentle nitrogen stream.

GC analysis: 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 an SPB-5 column (30 m x 0.25 mm, 0.25 �m film thickness) with an oven temperature program of 60�C (2 min), then at 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. Quantitative data of the constituents were obtained by the internal standard method from FID electronic integration without the use of response factors.

GC/MS analysis :The extract was analyzed using 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 impact electron mode (70 eV) at 230�C. Detection was performed in the scan mode between 30 and 400 Daltons.

Compounds were identified by comparing their spectra to those of the Wiley library or our IDENT library and also by comparison of their GC retention indices to those of standard compounds and data from literature (2,3).

Results and Discussion

The volatile constituents of karanda fruit were obtained by simultaneous steam distillation-solvent extraction and analyzed by GC and GC/MS using fused silica capillary columns. Table I summarizes the qualitative and quantitative analyses of the fruit volatiles according to order of elution on the SPB5 column. The yield of total volatiles, estimated by the addition of a measured amount of internal standard to the pulp, was approximately 70 mg/kg of fruit pulp.

One hundred and fifty constituents were identified, all of them reported for the first time as volatile components of karanda. A rough survey of the chemical classes represented in this fruit flavor was as follows: alcohols comprised the largest class of volatiles (29.8%), while the composition of the other classes of compounds was as follows - terpenoids, 24.0%; esters, 23.1%; fatty acids, 11.9%; carbonyls, 2.2%; furanoids, 1.7%; and others, 4.2%.

Major constituents found in karanda flavor were isoamyl alcohol (6.65 ppm), isobutanol (6.06 ppm) and [beta]-caryophyllene (5.94 ppm). Some compounds present, e.g. furfural, could probably be degradation products of ascorbic acid and sugars. It has been reported that acid treatment and even distillation induce the oxidation of ascorbic acid (4). Nevertheless, the concentrate was found, on appropriate redilution with water, to possess the characteristic karanda fruit flavor.

Odor descriptors provided by an informal sensory panel included fruity-winey, floral-woody, acidic and pungent.

Taken together, these results indicate that the exotic flavor character of karanda fruit is the interaction of fruity-winey (isoamyl alcohol), floral-woody ([beta]-caryophyllene), with acidic and pungent (fatty acids) notes contributing to the complexity of the fruit flavor.

References

1. D. Sturock, Fruits for Southern Florida. Southerwestern Printing Co., Inc., Stuart, FL (1959).