Extraction and Physiochemical Characterization of Oils Obtained from Selected Under-Utilized Oil Bearing Seeds in Nigeria

Abstract

The oils extracted from selected underutilized seeds in Nigeria; Rubber seeds (RS), African pear seeds (APS) and Cotton seed (CS) using n-hexane were analyzed for their physico-chemical properties viz: melting point, relative viscosity, free fatty acids, saponification value, iodine value, acid value, percentage unsaponifable matter, ester value and heat of combustion, using standard methods. The % oil contents in the seeds were determined to be 42.967 ± 0.59%, 19.427 ± 0.13% and 35.433 ± 0.86% for RS, APS and CS respectively. The extracted oils were liquids at room temperature with oil extracts from APS and CS having pleasant odour with light green and golden brown colour respectively, however oil extract from RS had an unpleasant smell with brownish yellow colour. There was significant difference in the physiochemical properties investigated. The acid value ranged from 6.840 to 32.000 mg KOH/g, the saponification values were high ranging from 173.115 to 185.333 mg KOH/g. The iodine value of (RSO), (139.703 g I2/100g) classified it as a semi - drying oil. The peroxide value of RSO (14.300 mequiv O2/kg oil) falls above the Standard  Organization of Nigeria (SON) recommended peroxide value (10 mequiv O2/kg oil) for edible oils and its free fatty acid (16.096 %) is also above the recommended 5% which makes it non-edible oils. The physicochemical properties of the oils suggest that they exhibit edible and industrial  potentials.

Keywords: African Pear, Cotton, Oil, Rubber, Seed