Green Ultrasonic Extraction of High Stearic–High Oleic Sunflower Oil Using Isopropanol as Solvent

Abstract

Ultrasound-assisted extraction (UAE) using absolute isopropanol (AIP) was evaluated as a sustainable alternative to hexane for the recovery of high stearic–high oleic (HSHO) sunflower oil. Process variables—ultrasonic amplitude, extraction time, and temperature—were optimized using response surface methodology to maximize total extract (TE) and oil fraction (OF) yields. Under optimal conditions (57% amplitude, 59 min, 36°C), UAE achieved 85% of the OF yield established by conventional Soxhlet extraction (8 h, n-hexane), with a substantially shorter processing time, while achieving a 36.29% TE yield (dry basis). TE and OF yields were approximately 11% higher than those obtained through mechanically stirred batch extraction under equivalent conditions, thereby demonstrating the beneficial role of ultrasound in enhancing extraction efficiency. Scanning electron microscopy revealed extensive cellular disruption in ultrasound-treated samples, consistent with enhanced mass transfer. No statistically appreciable trend was observed in the fatty acid profile across extraction methods. At the same time, oxidative stability was greater for absolute isopropanol-extracted oils, despite their lower tocopherol content in relation to Soxhlet/n-hexane extracted oil, indicating the possible co-extraction of other antioxidants. The combination of ultrasound and AIP provides a safe, renewable, and efficient approach for the industrial-scale production of specialty oils, thereby improving process efficiency and potentially enhancing nutritional quality.