Physicochemical Characteristics Of Crude And Dehydrated Castor Oil From Local Wild Plants (ricinus Communis) From Five Selected Regions In Kenya

Abstract

Castor oil have a unique fatty acid i.e. C 18:1 ; 12-hydroxy-9-cis-octadecenoic acid which has influenced its applications. The oil has myriad uses in the manufacture of medicines, cosmetics, lubricants, paints and recently in bio fuels. In Kenya currently, no commercial cultivation and extraction of castor oil is being done to harness the economic potential in this plant. This necessitated analysis of the oil yields and the quality of the oil obtained from the local plants prior to promoting their cultivation. Castor oil seeds were collected from Rumuruti in Laikipia county, Naivasha in Nakuru county, Limuru in Kiambu county, Maragua in Murang’a county and Kibwezi in Makueni County. Solvent extraction and cold pressing was used to extract the oil. The percentage moisture content of the seeds ranged from 4.8 ± 0.2 to 6.0 ± 0.2. Percentage oil yields were found to range from 43.07 ± 1.58 to 51.44 ± 1.02. Other physicochemical parameters determined, averaged and compared for both solvent extracted and cold pressed oil were; specific gravity (0.9697 ± 0.0085 for both solvent extracted and cold pressed), refractive index (1.471 ± 0.0009 for solvent extracted and 1.472 for cold pressed), flash point in 0C (260 ± 11 for solvent extracted and 272 ± 3 for cold pressed). Kinematic viscosity in cSt at 40 0C (I72.76 ± 5.99 for solvent extracted and 193.93 ± 10.01 for cold pressed), acid value (ranged from 5.35 ± 0.15 to 19.38 ± 0.37 for solvent extracted and 1.17 ± to 10.24 ± 0.09 for cold pressed), saponification value (180.60 ±1.12 mgKOH/g for solvent extracted and 182.21 ± 4.26 mgKOH/g for cold pressed). Iodine value (86.21 ± 0.92 for solvent extracted and 83.53 ± 0.69 for cold pressed), percentage unsaponifiable matter (0.78 ± 0.08 for solvent extracted and 0.14 ± 0.04 for cold pressed) and the Lovibond color number (0.5 ± 0.05 for solvent extracted and 0.2 for cold pressed). All the parameters tested met the requirements of KS 03-799: 1989 ‘Specification for castor oil for cosmetic industry’ except for specific gravity and acid values which had slight deviations. vi Both the solvent and cold press crude castor oils were dehydrated after neutralization. The iodine value for the dehydrated oils was found to rise to 140.71 ± 0.92 for solvent extracted and 137.44 ± 1.67 for cold pressed while the kinematic viscosity decreased to 156.98 ± 1.10 for solvent extracted and 161.52 ± 0.58 for cold pressed. The set to touch time for both the solvent and cold extracted dehydrated oil was found to be 36 hours with a drying time of three days. The oils kinematic viscosity and iodine value were found to meet the ASTM D961-86 requirements for oil used in the coatings industry.