AROMA COMPOUNDS IN MINOR CITRUS SPECIES GROWN IN AUSTRALIA

Abstract

The volatile components in the peel oil and juice of three citrus species, Buddha's hand citron (Citrus medica var. sarcodactylus), kaffir lime (Citrus hystrix) and Persian lime (Citrus latifolia), were analysed in this research. The aroma compounds present in the juice of the citrus fruits were isolated by low temperature vacuum distillation. This was conducted at a temperature of 28°C. The volatile compounds were condensed in three cold traps which were held at temperatures of -12, -79 and -192°C respectively. These temperatures were achieved by using frozen 20% NaCl solution, dry ice in ethanol and liquid nitrogen respectively. The volatiles were combined together and further extracted with the simultaneous distillation extraction (SDE) technique, using dichloromethane as the extracting solvent. The concentrated extract was then analysed by gas chromatography-mass spectrometry (GC-MS). In the case of the peel oils, the aroma compounds were extracted with SDE before analysing with GC-MS. The components which were identified from the peel oils and juice include monoterpenes, oxygenated monoterpenes and sesquiterpenes. The major components were limonene, γ-terpinene, β-pinene, 4-terpineol and α-terpineol. It was observed that the volatile components found in the peel were of higher concentration as compared to their concentration in the juice. The efficiency of the vacuum distillation was also investigated in this research. Aroma profiles of the volatile compounds present in citrus fruit were identified through a direct injection into GC-MS and also after the peel or juice had undergone vacuum distillation and SDE.