Optimization of ultrasound-assisted enzymatic extraction of walnut kernel oil using response surface methodology

摘要

In this study, ultrasound-assisted enzymatic technique was investigated using n-hexane solvent for walnut oil extraction. To achieve this goal, ultrasonic pre-treatment time (0-70 min) and enzymatic extracting conditions; namely, cellulase concentration (0-2 %) and incubation time (60-240 min) were optimized using response surface methodology. The optimal ultrasonic-enzymatic extraction treatment using n-hexane solvent was 47.37 min ultrasonic time, 2.00 % cellulase concentration and 110.91 min incubation time. This treatment resulted in significantly more EY (p = 0.001), TPC (p = 0.001) and IV (p = 0.01) and low level of PV (p = 0.01) of extracted walnut oil, compared to stirring incubation extraction using n-hexane solvent, ultrasound-assisted aqueous enzymatic extraction, and aqueous stirring incubation extraction treatments. Gas chromatography-mass spectroscopy showed higher content of unsaturated fatty acids of extracted oil; and scanning electron microscopy showed more pores and interspaces of walnut powder residues of optimal ultrasonic-enzymatic extraction using n-hexane solvent than those of stirring incubation treatment using n-hexane solvent.