Efficient and green ultrasound-assisted supercritical carbon dioxide extraction of squalene from Amaranthus cruentus grains.

Squalene is a nutraceutical dietary component that shows potent antioxidant activity and supports cardiovascular health. This study employed an ultrasound-assisted supercritical carbon dioxide extraction (UASCE) using a 40 kHz ultrasonic bath (30 L, inner dimensions 500 × 300 × 200 mm) to extract squalene from Amaranthus cruentus grains. Response surface analysis identified optimal temperature, pressure, and ultrasonic energy density parameters as 47 °C, 20 MPa, and 0.17 W mL-1, which lead to the highest squalene yield of 4.18 ± 0.04 mg g-1. Under the respective optimized conditions for UASCE and conventional SCE, UASCE achieved an 11.5 % higher SQY, together with lower CO2 and energy consumption, a shorter extraction time, and milder temperature and pressure conditions, while maintaining favorable oil quality. Scanning electron microscopy observations revealed that UASCE-treated particles exhibited an uneven surface structure with dense micro-fissures, which likely facilitated solute release and solvent penetration during ultrasonic treatment. The developed Sovová model successfully described the extraction kinetics. The driving force governing the extraction process was found to be dominated mainly by convective mass transfer. Ultrasound boosted mass transfer coefficients and abridged the typical extraction stages. Furthermore, the experimental solubility data were satisfactorily correlated using the Chrastil model and compared with two recently proposed density-based semi-empirical models developed by Sodeifian et al. Ultrasonic assistance effectively enhanced squalene solubility in the supercritical solvent and a clear crossover behavior was identified. Overall, this hybrid technique provides an efficient and eco-friendly way to extract squalene from plant parts.