Influence of Variety and Pre-treatment on Oil Properties of Mechanically Expressed Castor Oil

^*F. A. Oluwole¹, N. A. Aviara², B. Umar² and A. B. Mohammed¹

¹Department of Mechanical Engineering, University of Maiduguri, Maiduguri, Nigeria ²Department of Agricultural and Environmental Resources Engineering, University of Maiduguri, Maiduguri, Nigeria

³Department of Agricultural and Environmental Resources Engineering, University of Maiduguri, Borno State, Nigeria.

Accepted 03 January 2015

Abstract

Oil was mechanically expressed from four varieties of pre-treated castor seeds, namely: white big size (WBS), black big size (BBS), grey medium size (GMS) and grey small size (GSS) using hydraulic press. The expressed oils were analyzed to investigate the effects of pre-treatment (nature of seed and heating method) on some of these properties (acid value, saponification value, iodine value, specific gravity, viscosity, refractive index, pH value and peroxide value) of these varieties. Mathematical models for acid and saponification values of castor oil were developed by factorial analysis. The studied factors were seed variety (WBS, BBS, GMS and GSS), nature of seed (dehulled and undehulled seeds) and heating method (raw, boiled and roasted seeds). It was revealed that acid value and saponification value were significantly affected by seed variety and heating method at 5% level of significance, while iodine value, specific gravity, viscosity, refractive index, pH value and peroxide value were not statistically affected by seed variety, heating method and nature of seed. The model predicted that the maximum and minimum acid values were 3.88% and 0.66% from WBS (roasted and undehulled) and GMS (raw and dehulled) respectively. While the maximum and minimum saponification values were 195.19% and 166.53% from BBS (roasted and undehulled) and GMS (raw and dehulled) respectively.

Keywords: Castor seed, castor oil, oil expression, oil properties, seed variety, model equation