Volatile Constituents of Calamondin Peel and Juice (Citrus madurensis Lour.) Cultivated in the Philippines

Journal of Essential Oil Research: JEOR, Jan/Feb 2005 by Takeuchi, Hiroaki, Ubukata, Yoshihito, Hanafusa, Masayoshi, Hayashi, Shuichi, Hashimoto, Seiji

Abstract

The volatile constituents of fresh calamondin (Citrus madurensis Lour.) cultivated in the Philippines were investigated by GC and GC/MS. As a result, 58 and 98 compounds were identified from the peel and juice volatile concentrates, respectively. The characteristic flavor components of calamondin were examined by GC-olfactometry. Limonene, cis-linalool oxide, linalool, α-terpineol, (E,E)-2,4-decadienal, and methyl N-methyl anthranilate had high flavor dilution factors. Additionally, the enantiomeric ratio of limonene, linalool, terpinen-4-ol and α-terpineol in calamondin were measured by chiral GC.

Key Word Index

Citrus madurensis, Rutaceae, calamondin, extract composition, GC-olfactmetry, enantiomeric ratio, limonene.

Introduction

Calamondin (Citrus madurensis Lour; syn. C. mitis Blanco; C. macrocarpa Bunge), a dwarf citrus fruit native to the Philippines, is widely distributed in southeast Asia. The fruit looks like kumquat, and its flesh is juicy and sour, Calamondin has been used as a garnish for fish and chicken dishes in the Philippines. In 1958, Nigam et al. performed a preliminary analysis of C. macrocarpa (1). In a calamondin essential oil produced from fruit cultivated in Florida, 56 components from the peel oil (2) and 20 components from the juice oil (3) were reported.

In the present study, the volatile constituents of calamondin (C. madurensis) cultivated in the Philippines we re investigated by GC and GC/MS, and their characteristic flavor components were examined by aroma extract dilution analysis (AEDA). Additionally, the enantiomeric distribution of limonene, linalool, terpinen-4-ol and α-terpineol in calamondin extracts were measured by chiral GC.

Experimental

Materials: Mature calamondin fruits were obtained from the Philippines, in November, 1996.

Extract isolation: Peel extract: The peel of calamondin (4.15 g) was extracted with hexane (24 h). The extract was dried over anhydrous magnesium sulfate, followed by concentration to give an extract (0.08g), [α]D25 46.84°(c=0.158, MeOH). The extract was a liquid of orange color which had fresh and green odors similar to those of mandarin and lime. Juice extract: The flesh of calamondin (68.6 g) was mixed with water (50 g) by kitchen-juicer, filtered and then concentrated. The recovered flavor obtained from the concentration was saturated with salt, and extracted with diethyl ether. The extract was dried over anhydrous magnesium sulfate, followed by concentration to give an extract (0.003 g), [α]D25 26.83°(c=0.902, MeOH). This juice extract was a liquid of orange color which had a sweet and juicy odor similar to mandarin and orange juice.

GC: GC analyses were performed on a Shimadzu gas Chromatograph (GC-17A) equipped with flame ionization detector, using a capillary column (TC-WAX, 60 m × 0.25 mm, df = 0.25 µm). Helium gas was used as the carrier gas at 1.2 mL/min. Oven temperature was held at 80°C for 5 min and then programmed to 240°C at a rate of 3°C/min. Injector and detector (FID) temperature were 250°C. Quantitative data were obtained from peak area measurements without the use of correction factors.

GC/MS: GC/MS analyses were performed on a Hewlett-Packard 5890 Series II plus Chromatograph linked to a Hewlett-Packard 5972A mass spectrometer system equipped with a capillary column (TC-WAX, 60 m × 0.25 mm, df = 0.25 µm). Helium gas was used as the carrier gas at 1.2 mL/min. The ionization energy was 70 eV. Oven temperature was held at 70°C for 5 min and then programmed to 240°C at a rate of 3°C/min. Injector and MS temperatures were 240°C and 150°C, respectively. Identification of the oil components was established using a Wiley MS Data Library (4).

Chiral analysis: Preparative gas chromatography was performed on a Hitachi 663-30 gas Chromatograph equipped with a thermal conductivity detector, using a glass column (3 m × 3mm, PEG20M Uniport HP 10% 60/80 mesh). Helium was used as the carrier gas at 36 mL/min. Oven temperature was programmed from 90°- 230°C at a rate of 4°C/min. Injector and detector (TCD) temperatures were 250°C.

Chiral gas chromatography was performed on a Shimadzu gas Chromatograph (GC-17A) equipped with aflame ionization detector, using a WCOT fused silica column (CP-cyclodextrinβ-2,3,6-M-19, 50 m × 0.25 mm, df = 0.25 µm). Helium gas was used as the carrier gas at 1.2 mL/min. Oven temperature was held at 50°C for 5 min and then programmed to 120°C at a rate of 1°C/min. Injector and detector (FID) temperatures were 200°C and 210°C, respectively.

MDGC: MDGC was carried out on a dual oven linked system comprised of a GL-Science GC353 (GCl) containing the pre-column and an HP 5890 Series II (GC2) containing the analytical column.

Pre-column: TC-WAX (60 m × 0.25 mm, df = 0.25 µm) Column temperature: 80°C (5 min)~240°C (3°C/min). Injector and detector (FID) temperature: 270°C.

Analytical column: CP-Chirasil Dex CB (60 m × 0.25 mm, df = 0.25 µm). Column temperature: 80°C (45 min)~220°C (2°C/min). Injector and detector (FID) temperature: 220°C.