Oil extraction from tiger nut (Cyperus esculentus L.) using the combination of microwave-ultrasonic assisted aqueous enzymatic method - design, optimization and quality evaluation

Microwave-ultrasonic assisted aqueous enzymatic extraction (MUAAEE) was applied to extract tiger nut oil (TNO). The conditions of MUAAEE were optimized by Plackett-Burman design followed Box-Behnken design. An oil recovery of 85.23% was achieved under optimum conditions of a 2% concentration of mixed enzyme including cellulase, pectinase and hemicellulase (1/1/1, w/w/w), particle size <600 μm, microwave power 300 W, ultrasonic power 460 W, radiation temperature 40 °C, time 30 min, enzymolysis temperature 45 °C, pH 4.9, liquid-to-solid ratio 10 mL/g and time 180 min. Oil by MUAAEE revealed the similar fatty acid compositions, triglyceride compositions, thermal behaviour and flavour compared with oil by Soxhlet extraction (SE), while the oil quality of MUAAEE is superior to that of SE. Scanning electron microscopy revealed that structural disruption of tiger nut caused by MUAAEE facilitated the oil extraction. Results suggest that MUAAEE could be an efficient and environment-friendly method for extraction of TNO.

Keywords: Box-Behnken design; Microwave-ultrasonic assisted aqueous enzymatic extraction; Oil analysis; Plackett-Burman design; Tiger nut oil.