Rubber seed oil extraction: Effects of solvent polarity, extraction time and solid-solvent ratio on its yield and quality

Abstract

Abstract Two solvents (isopropanol and n-hexane) with different polarity were employed in oil extraction from rubber seed with the aim of determining their effects on its yield and properties. The solvent extraction process deployed through Soxhlet technique was modeled and vital parameters affecting the characteristics of the rubber seed oil (RSO) were identified and optimized by D-Optimal design. Physical and chemical characteristics of the RSO were examined. The fatty acid content and functional groups in the RSO were investigated using gas chromatography and Fourier transform infrared (FT-IR) techniques, respectively. Optimum RSO yield of 63.14 wt% was observed in 2.7 h using solid:solvent ratio of 0.05 g/mL and n-hexane (a non-polar solvent). Maximum RSO yield obtained with isopropanol (a polar solvent) was 56.7 wt% in 3 h using solid:solvent ratio of 0.05 g/mL. Statistics of the model developed demonstrate that solid:solvent ratio had the highest impact on the RSO yield followed by solvent type. Unlike fatty acid content of the RSO, both the quality and yield were affected by isopropanol and n-hexane. In both cases of the solvents, the RSO samples obtained were highly unsaturated (79%) with linoleic and oleic being the main fatty acids. The fatty acid contents were confirmed qualitatively with FT-IR spectra showing regions of double bond stretching and bending vibrations of esters of the triglycerides and trans-unsaturation. The quality of the RSO showed that it is a viable feedstock for oleochemical industries such as biodiesel but needs acid treatment preceding to its transesterification.