Modelling of the Effect of Pretreatment Methods, and Time on the Yield of Eucalyptus Essential Oil Using Response Surface Methodology

The wide application of essential oils as a result of their medicinal properties has prompted continuous research towards determining factors affecting their yield. One of such essential oils with medicinal properties is Eucalyptus camaldulensis. In line with this trend is the aim of this study centred on modelling the effect of pretreatment methods applied to plant leaves and the extraction time on the yield of essential oils from Eucalyptus camaldulensis. Different polynomial regression models were developed showing the relationship between the pretreatment methods, time and the yield of oil using response surface methodology in Design Expert Version 11. The different multiple regression models were fitted to experiment data and the best model was further validated using analysis of variance (ANOVA), and analysis of residuals. Further optimization of the extraction of the yield was carried out using the desirability function in Design Expert Version 11. Results of the study showed that at optimum values of extraction time of 145 min, a yield of 1.48% was obtained with chilled pretreated leaves. The model that best explains the data was a linear model and the model showed a good fit with the experimental data, with a coefficient of multiple determination (R2) value of 0.9938. The study would pave the way for further scale-up in the recovery of essential oils from Nigerian-based Eucalyptus camaldulensis specie.