A mechanistic insight into supercritical fluid - substrate interaction in supercritical CO2 extraction of oils from Moringa oleifera and Eucalyptus

[Truncated] Supercritical CO2 extraction of oils from Moringa oleifera and Eucalyptus was studied using a Supercritical Fluid Technologies Inc. customized Supercritical Water - Supercritical Fluid Extraction (SCW-SFE) system. This new experimental technique was validated by comparing against the results from the conventional methods of Soxhlet extraction and hydro-distillation. Firstly, the yields and compositions of the oils from Moringa oleifera seeds and leaves were extracted using supercritical CO2 and compared with those obtained by Soxhlet extraction. Experimental results revealed that the oil yield from the supercritical fluid extraction was lower than that from the Soxhlet extraction. The chemical compositions of all oils were analysed and the results indicated that the fatty acid compositions of the seed oil extracted by these two methods were very similar. However, there was a significant difference in the Moringa oleifera leaf oil, in which the number of compounds identified in the Soxhlet extraction was significantly greater than that of the supercritical fluid extraction. Secondly, the Eucalyptus leaves were subjected to extraction using all of the three methods. The experimental results showed that Soxhlet extraction achieved the highest yield, while hydro-distillation produced the lowest yield among the three methods. With respect to the oil compositions, the hydro-distillation method extracted only volatile compounds, while the supercritical fluid extraction and Soxhlet extraction methods extracted not only volatile compounds, but also heavy molecular weight compounds.