Optimization of SC-CO2 extraction of oil from almond pretreated with autoclaving

Supercritical carbon dioxide (SC-CO2) extraction parameters affecting oil recovery from almond were optimized through response surface methodology (RSM). The optimum extraction conditions were as follows: extraction pressure, 44.1 MPa; extraction temperature, 43.8 °C; dynamic extraction time, 93.6 min; and CO2 flow rate, 10.1 mL/min. Under these conditions, a mean value of 86.54 ± 0.66 g/100 g (n = 3) was observed, which is well matched with the predicted value of 87.32 g/100 g. Furthermore, the effects of autoclaving pretreatment for the almond particles on the oil recovery, fatty acids' composition, and almond particles' microstructure were also investigated by calculating the percentages of the oil yield, gas chromatograph fitted with a mass spectrometer (GC–MS), and scanning electron microscopy (SEM) analysis, respectively. The results showed that autoclaving pretreatment had minor modifications of the fatty acids' profile of the extracted oil, but greatly promoted the disturbing of almond cell walls, and increased the oil recovery by 6.44%.