Homogenization-circulating ultrasound in combination with aqueous enzymatic pretreatment for microwave-assisted extraction of kernel oil and essential oil from the fruit of Litsea cubeba

Homogenization-circulating ultrasound in combination with an aqueous enzymatic pretreatment microwave-assisted extraction (HCUEPM) technique was successfully applied to extract kernel oil and essential oil from Litsea cubeba fruits. After screening the types and concentrations of enzymes, a 3 % pectinase aqueous solution was chosen. The Plackett-Burman design was used to screen eight parameters that might affect the yield of kernel oil and essential oil to identify significant variables. The best conditions were then predicted by further optimizing statistically significant factors via the Box-Behnken design. The optimal conditions were as follows: stirring speed of 1000 r/min, environmental pH of 5, homogenization time of 4 min, duty cycle of 20 %, ultrasound irradiation power of 400 W, incubation temperature of 52.78 °C, liquid-solid ratio of 9.31 mL/g, and incubation time of 2.53 h. Three parallel experiments were conducted under these conditions, yielding actual kernel oil at 240.56 ± 11.07 mL/kg DW and essential oil at 64.89 ± 3.1 mL/kg DW, which are close to the theoretical values. Compared with the HCUEPM method, the homogenization-microwave-assisted hydrodistillation (HMHD) method yielded 65.63 ± 3.2 mL/kg DW of essential oil but could not extract kernel oil. These findings demonstrate that the HCUEPM used in this study can efficiently extract a significant amount of kernel oil and essential oil from L. cubeba fruits in a short period of time. GC-MS analysis of the kernel oil and essential oil extracted via different methods revealed no significant differences in composition. The main components of the essential oil were D-limonene, trans-citral, cis-citral, and citronellal. The main components of the kernel oil were C