PHYSICOCHEMICAL PROPERTIES AND INHIBITORY EFFECTS OF ESSENTIAL OILS FROM SELECTED LOCAL SPICES

Abstract

Spices are rich in essential oils and are known to possess antiviral, antibacterial, antifungal and insecticidal properties. This study evaluated the inhibitory effect and physicochemical properties of essential oil from some selected spices. Cinnamon, ginger and garlic were pulverized and extracted using the soxhlet method with n-Hexane. The extracted oils were subjected to physicochemical and microbial analysis. Results showed that ginger gave the highest oil yield (7.01%) in comparison with cinnamon and garlic: 2.75 and 1.33 % oil yields at respective 10.62, 14.29and 11.16 % moisture contents. Iodine value, acid value and free fatty acid value was significantly (p<0.05) higher in cinnamon oil (506.15, 20.66 mgKOH/g and 10.33 mgKOH/g respectively) compared to the respective 348.65, 15.41 mgKOH/g and 7.71 mgKOH/g for ginger and 128.15, 17.90 mgKOH/g and 8.95 mgKOH/g for garlic. Saponification value was significantly (p<0.05) higher in ginger (226.15mgKOH/g) than in cinnamon (214.75 mgKOH/g) and garlic (198.54 mgKOH/g). A significantly high (p<0.05) peroxide value was observed in garlic with 247.12 milli eq/Kg, and 234.15 and 247.12 milli eq/Kg for cinnamon and ginger respectively. Cinnamon oil was observed to be the most potent against the tested microorganisms, showing maximum inhibition zones of 0.9 cm for E. coli, 1.1 cm for P. aeruginosa and 2.4 cm for each of K. pneumonia, Serratia spp. and S. aureus. Result from the study revealed that the extracted oils are not fit for consumption, highly susceptible to rancidity and oxidation but are of good potential use in paint and soap making.