Efficient and selective extraction of unsaturated fatty acids from macadamia nut oil: Design and application of...

Macadamia nut oil is abundant in unsaturated fatty acids (UFAs) that are beneficial to human. Nevertheless, due to the high oil solubility of these UFAs, direct extraction from macadamia nut oil poses a significant challenge. This study used supramolecular deep eutectic solvents (SUPRADESs) as green media to extract UFAs from macadamia nut oil under the assisted of ultrasound. Positively charged N-cyclodextrin (N-CD) was synthesized as a hydrogen bond acceptor (HBA), which was then combined with natural hydrogen bond donors (HBDs) to prepare a series of SUPRADESs. The effects of SUPRADES composition, HBA/HBD molar ratio, water content and extraction conditions (ultrasonic time and ultrasonic temperature) on UFAs extraction yield were evaluated via single-factor experiments, and the extraction conditions were subsequently optimized using response surface methodology (RSM). Results showed that the SUPRADES prepared from N-CD and hexanol exhibited the highest extraction efficiency. The extraction yield of UFAs reached up to 178 mg/g, which was significantly higher than the extraction yield achieved by directly extracting UFAs from raw macadamia nuts using organic solvents. Furthermore, the SUPRADES exhibited high selectivity for UFAs, resulting in an extract with the saturated fatty acids (SFAs) content of less than 1 %. Density functional theory (DFT) was employed to elucidate the extraction mechanism and green metric assessments confirmed the environmental advantages of this method. This work developed an effective method for extracting UFAs from Australian nut oil using ultrasound assistance.