Investigation on the extraction yield, quality, and thermal properties of hempseed oil during ultrasound-assisted extraction: A comparative study

The efficiency of ultrasound-assisted extraction (UAE) was evaluated for hempseed oil extraction using response surface methodology (RSM), and the obtained optimum point was 91 W and 10 min. In which, the extraction yield was obtained 33.61% w/w which was lower than Soxhlet extraction (37.93% w/w), whereas the process time was shorter than Soxhlet method (10 min vs. 8 hr). Extracted oil by UAE showed better oxidation stability and stronger antioxidant activity. TOTOX values were 2.95 and 16.49 and IC50 values were calculated as 29.54 and 32.47 mg/ml, for UAE and SE, respectively. Tocopherol, fatty acid composition, and thermal behavior of oils were analyzed by HPLC, GC, and DSC, respectively. Results showed that UAE can effectively extract oil-soluble components such as tocopherols with less deterioration effect. Fatty acid profiles did not show a remarkable difference but DSC indicated that partial difference in fatty acid composition and possibly triglycerides occurred in different thermal attributes. Practical applications Plant seed oils such as hempseed oil due to having a high amount of polyunsaturated fatty acids (PUFAs) can be applied in many application fields considering food enrichments and capsules including PUFAs which are too necessary for human bodies. So, oil extraction of such these sources is so highlighted and critical due to being sensitive to oxidation conditions. Novel extraction procedures are so promising caused by their shortened process time and presenting high-quality products with high extraction efficiency comparable with Soxhlet extraction. UAE is a method based on bubble cavitation which improves oil extraction. It reduces extraction time by considering the high quality of extracted oil due to its high antioxidant activity capacity. In a recent study, ultrasound-extracted oil compared with Soxhlet which exhibited that the process time was significantly reduced with presenting better oil oxidative stability and acceptable antioxidant activity resulted from high tocopherol extraction and the eventually better remaining of bioactive components due to lower deterioration effects of UAE. Additionally, the determined fatty acid compositions did not show the highlighted difference. The results by differential scanning calorimetry indicated that not only fatty acid compositions can alter the thermograph peaks but also crystal structures possibly affected the associated attributes.