Ultrasound and low-pressure supercritical CO2 extraction: A synergistic approach to hemp seed oil extraction

Abstract

Supercritical CO₂ extraction was employed to acquire cannabidiolic acid (CBDA), cannabidiol (CBD), cannabinol (CBN), and tetrahydrocannabinolic acid (THCA) at temperatures ranging from 40 to 60 °C. The highest yields of cannabinoids were achieved under reduced pressure conditions of 200 bar. Ultrasonication pretreatment on hemp seeds prior extraction showed little impact on chlorophyll and carotenoid contents. Oils extracted from ultrasonically treated hemp seeds exhibited a higher total phenolic content at 200 bar and 50 °C for 3 h compared to treatment at 600 bar and 50 °C for 1 h, correlating with the antioxidant activities. Analysis of the extracted hemp seed oil showed elevated levels of polyunsaturated fatty acids, particularly linoleic acid. The extracted hemp seed oils showed polyunsaturated fatty acids to saturated fatty acids (PUFAs/SFAs) ratios of 6.58–7.22, n-6/n-3 ratios of 3.96–4.18, and index of atherogenicity (IA) values ranging from 0.07 to 0.09. Thrombogenic potential, reflected by index of thrombogenicity (IT) values, varied between 0.12 and 0.13 in the extracted oils. Hydrogen/hydrocarbon (H/H) ratios for hemp seed oils were between 11.66 and 13.28. Ultrasonication pretreatment significantly altered cannabinoid profiles of the oils. Low pressure extraction favored CBDA and THCA, while high pressure extraction negatively impacted all cannabinoids. In addition, the ultrasonic pre-treatment of hemp seeds before supercritical CO₂ extraction minimally affected fatty acid composition and nutritional indices, including PUFAs/SFAs ratio, n-6/n-3 ratio, IA and IT values, and H/H ratio. A combination of pretreatment and low-pressure extraction at 50 °C better maintained stability of the oil during storage at 25 °C than high pressure extraction. Conversely, untreated oil extracted at high pressure exhibited the lowest peroxide values after a prolonged storage at 55 °C, suggesting complex interactions between pretreatment, extraction, and storage conditions.