Optimization and evaluation of the ultrasound-enhanced subcritical water extraction of cinnamon bark oil

Ultrasound-enhanced subcritical water extraction (USWE) of cinnamon oil was studied by self-made apparatus. Response surface methodology was applied to optimize the USWE conditions of cinnamon oil. USWE was compared with three other methods in terms of extraction conditions, cinnamon oil yield, quality and composition of cinnamon oil. Antioxidant activities of cinnamon oil from USWE were assessed. Finally, scanning electron microscopy was performed for the cinnamon particles before and after extraction to understand the effect of USWE on the physical structure. Results showed that the optimal conditions were extraction temperature of 140 °C, extraction time of 25 min, pressure of 5 MPa, a liquid-to-solid ratio of 8 mL/g, ultrasonic power of 145 W, ultrasonic frequency of 18.5 KHZ, and continuous ultrasonic treatment. The maximum yield of cinnamon oil and E-cinnamaldehyde were 1.78% and 12.662 mg/g, respectively. Extraction time of USWE was the shortest and equivalent to 1/10 that of steam distillation. The amount of desirable cinnamaldehyde from USWE was much higher than those obtained by other methods. Antioxidant activity assay indicated that cinnamon oil from USWE exhibited strong antioxidant activity. The results show that USWE is an effective potential technology for extracting cinnamon oil with good antioxidant activity. •The conditions for extraction of cinnamon oil by USWE were optimized.•USWE was evaluated by comparing with three other extraction methods.•Antioxidant activities of cinnamon oil from four extraction methods were assessed.•The effect of USWE on the physical structure was investigated.•USWE is an effective method to extract essential oil with good antioxidant activity.