Influence of Inherent Moisture Content on the Deformation Properties of Coconut Tissues During Mechanical Oil Expression

Abstract

The effect of moisture content on the deformation properties of coconut (Cocos nucifera) endosperm under mechanical uni-axial compression during a simulated oil expression situation was investigated. Fresh coconut samples at 45% moisture content (wet basis) and prepared samples at 3%, 7%, 11% and 15% wet basis moisture content were used. Results showed that tissues at higher moisture content (11 and 15%) had lower compressive strength hence lower forces at bio-yield point than drier  samples and they also experienced higher deformation at bio-yield point. Low moisture samples (3% and 7%) required more force to reach their bio-yield points at 17.7 N and 15.3 N respectively as compared to  specimens with moisture content of 11% and 15% which reached bio yield points at 11.4 N and 11.5 N respectively . Results showed that for samples at 3%and 7%wet basis moisture content the difference between bio-yield and oil-points was not significant (P>0.05) but there was a significant difference (P<0.05) for samples kept at 11% and 15% moisture contents. The study confirmed that moisture content has an important role in the deformation of coconut specimen. The compressive force required to deform the cellular structure decreased with the increase in moisture content with 11%moisture content (wet basis) providing the optimum condition. Results from this study has revealed that higher force would be required to express oil from drier oilseeds whereas relatively low forces are adequate to express oil from oil seeds kept at around 11% moisture content. This has high implication on the amount of energy required for oil expression and it is being recommended that further studies be carried out on the influence of moisture content in oil expression.

Key words: Coconut, deformation, compression, bio-yield point, oil-point, moisture content