Kolkhoung (Pistacia khinjuk) kernel oil quality is affected by different parameters in pulsed ultrasound-assisted solvent extraction

• The pulsed ultrasound-assisted solvent extraction was shown to be very efficient in the extraction of oil.
• Ultrasound influenced entropy more than enthalpy in the rates of oil extraction.
• The fatty acid and oxidation of the oil were not affected by the ultrasound.
• The pulsed ultrasound-assisted solvent extraction increased tocols content of extracted oil.

In this study, the effect of three amplitudes of pulsed ultrasound-assisted solvent extraction (PUASE) (0, 25, and 50%; 100 W, 30 kHz; the 0% treatment serving as control) on kinetics, yield and quality of extracted oil from Kolkhoung kernel at different temperatures (30, 40, and 50 °C) was evaluated. The highest oil yield, 77.5% (w/w), was obtained for samples treated with PUASE at 50% amplitude and 50 °C. The kinetics of extraction were evaluated based on a second order mechanism. Increases in amplitude and temperature significantly increased initial extraction rate (h), saturated extraction capacity (Cs), and rate constant of extraction (k). The thermodynamic aspects of the extraction process showed that samples treated with PUASE have lower activation energy (Ea), frequency factor (A), enthalpy (ΔH++) and entropy (ΔS++) than control. Ultrasound influenced entropy (or A) more than enthalpy (or Ea) in the rates of oil extraction. However, these values were independent of ultrasound amplitude. Moreover, PUASE did not significantly affect fatty acid composition, peroxide value (PV), conjugated diene value (CDV) and anisidine value (AnV) of extracted oils, but temperature decreased linoleic and linolenic acid content and increased oxidation products of oils. PUASE also increased tocopherols and tocotrienols content of oils but temperature did not significantly affect them. Thus, PUASE increases kinetics and quality of extracted oil and improves extraction process.