Effects of the heating temperature during the press extraction process on the yield and quality of cosmetic argan oil

The effects of the temperature of the heating ring of the extraction cylinder during the press extraction of argan oil from unroasted kernels on the oil extraction yield and quality were investigated. Oil extraction experiments were carried out with an Ateliers Afyach P55 mechanical screw press that had one press cylinder equipped with a heating ring located on the outlet side. Tested heating ring temperatures were 60, 80, 100, 120, 140, and 160 °C, and a medium screw rotational speed of 5 rpm was applied. The temperature was monitored during the extraction process along the cylinder and at the oil outlet. Results showed a significant effect of the cylinder heating ring temperature on the oil extraction yield; higher yields were obtained in the 80–120 °C range, with the highest values obtained at 80 °C for crude oil and clarified oil (53–55% and 47% wt/wt, respectively). At 60 °C, the oil extraction process was difficult to realize because the cylinder jammed due to the presence of a considerable amount of residue particles in the extracted oil. The measured temperatures at different points along the press cylinder during the extraction process and the temperature of the oil extracted during the process were much lower than the temperature of the heating ring. The extracted oil temperature ranged between 45 and 68 °C. In addition, even though the effects of the temperature on the monitored quality parameters (free acidity, peroxide value, and UV absorbance) were significant, all of the extracted oils were of extra virgin grade. These results imply that heating the ring of the extraction cylinder to approximately 80 °C optimizes the performance of the press and results in a high oil yield without compromising oil quality.