Abstract:
Much of the work done in literature on Jatropha oil extraction were done at temperatures less than 40oC (normal atmospheric temperature). As a result of improper temperature conditioning during oil extraction more than 10% of total extractable oil is lost. This study investigated the effect of five different extraction temperatures on oil yield and quality of Jatropha curcas l. kernel in other to determine the optimum temperature for maximum oil yield and best oil characteristics. Oil was extracted from Jatropha curcas l. kernel by soxhlet extractor using normal hexane as the solvent and at five levels of temperature (40oC, 50oC, 60oC, 70oC and 80oC). Based on physico-chemical analysis, the oil was characterized. Oil yield, ash content, acid values, oleic acid values, iodine values, kinematic viscosity, density and hydroxyl values were measured at each temperature level. A 5×8 factorial in CRD experimental design with a total of 600 observations (5 temperature levels×8 levels of oil properties ×15 replications) was conducted. Data were analyzed using descriptive and inferential statistics with SPSS and Excel packages. The results show that temperature has significant effect on oil yield, ash content, acid value, oleic acid value, kinematic viscosity, density, iodine value and hydroxyl value. Oil yield was 33.35% by weight, at 40oC, and it increased to 44.41% by weight at 60oC. Thereafter oil yield fell to 41.55% by weight as extracting temperature rose to 80oC. Ash content values in the oil were 0.0017% by weight, 0.014% by weight, 0.019% by weight, 0.0346% by weight and 0.05% by weight at extraction temperatures of 40oC, 50oC, 60oC, 70oC, and 80oC respectively. At a temperature of 40oC the acid value of the oil was 3.11% by weight and increased by about 11.6%, 13.30%, 27.33% and 43.20% as extraction temperature rose to 50oC, 60oC, 70oC, and 80oC respectively. This indicates oil degradation. Temperature had significant effect on iodine value. Increase in temperature from 40oC to 80oC decreased iodine value from 3.05g/100g to 0.76g/100g. Kinematic viscosity was 41.62Cst at 40oC, 42.43Cst at 50oC, 43.30 at 60oC, 45.57 at 70oC and 47.83 at 80oC. These values were significantly different from each other at 5% probability level. The oil density and hydroxyl values were 0.91g/cm3 and 0.16gmole, 0.90g/cm3 and 0.11gmole, 0.90g/m3 and 0.069gmole, 0.91g/cm3 and 0.066gmole and 0.91g/cm3 and 0.078gmole at extraction temperatures of 40oC, 50oC, 60oC, 70oC, and 80oC respectively.