Optimization of Ultrasound-Assisted Extraction of Oil from Canola Seeds with the Use of Response Surface Methodology

In the current study, response surface optimization of canola oil extraction assisted by 35 kHz, 800 W ultrasound waves and with the use of hexane and 3:2 hexane–isopropanol at the proportion of 3/2 as solvents was conducted. The influence of extraction temperature (35, 45, and 55°C), ultrasound treatment time (30, 60, and 90 min), and solvent-to-canola (sample) ratio (5, 10, and 15 (% v/w)) on the percentage of the extracted oil and oxidative stability of the extracted oil was analyzed through Box-Behnken design. The achieved results revealed that the optimized conditions for canola oil extraction (22.39% efficiency) by hexane was 87 min ultrasound treatment at 55°C and solvent-to-canola proportion of 6.39 (% v/w). On the other hand, the optimized conditions for canola oil extraction (30.66% efficiency) by hexane–isopropanol mixture were 69.5 min ultrasound treatment at 55°C and solvent-to-canola ratio of 9.12 (% v/w). The obtained outcomes revealed that ultrasound waves significantly improved the extraction efficiency compared to Soxhlet extraction. The extraction efficiency was improved when hexane–isopropanol mixture was applied. In optimized condition, oxidative stability of the extracted oil has been achieved at 12.55 and 40.9 h, respectively, once hexane and hexane–isopropanol were used as solvents for extraction. Oxidative stability presented considerable enhancement with an increase in ultrasound treatment. Extracted oil with the use of mixed solvent (hexane–isopropanol) presented higher value for oxidative stability compared to the extracted oil with the use of hexane as a solvent. Comparison between the ultrasound-assisted and Soxhlet extracted oils with the use of gas chromatography presented no significant difference in their fatty acid profiles.