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Chemical Composition of Seed Oil from Roselle (Hibiscus sabdariffa L.) and the Kinetics of Degradation of the Oil during Heating
並列摘要
The aim of the study was to investigate the chemical composition and the kinetics of degradation of roselle seed oil during heating. The seed is a good source of oil (23.27%). The physical properties of the oil extracts showed the state to be liquid at room temperature and indicated that the oil had refractive index, 1.4652; the peroxide value, 3.15 (meq O_2/kg oil); free fatty acid, 0.82%; iodine value, 97.78%; saponification value, 198.45 and viscosity, 15.15 (mPa.s at 25℃). Gas liquid chromatography technique has been developed for identification and quantitative determination of total unsaturated and saturated fatty acids shows that the crude oil had 73.4 and 26.57%, respectively. DSC indicates the presence of two components in oil extracted. The first peak at low melting point appears at -20.53℃ (H_f= +3.00 J/g) and the second peak appears to -2.17℃ (H_f= +0.49 J/g). The degradation kinetic of the oil was also investigated. The thermal oxidation of the double bonds of the oil showed a first-order thermal oxidation kinetic and the Arrhenius plot yielded a straight line with a slope equivalent to activation energy of 9.041 KJ/mol. There is the possibility of considering the seed as feed supplement and its oil for industrial application.