(163c) Optimization of Surfactant-Assisted Hydrodistillation of Lemon Oil with Response Surface Methodology

The surfactant-assisted hydrodistillation of lemon oil from lemon rind was performed with a mixture of Tween 40 and Tween 85. The response surface methodology (RSM) was applied to systematically optimize the parameters of the extraction process, including the surfactant concentration in the extractant, the extracting time, and the ratio of liquid extractant to solid rind. The apparent solubility of lemon oil (LO) by surfactant solution and the shelf stability of the prepared LO emulsion were investigated. Results showed that the optimal condition was ca. 1550 ppm as the concentration of the mixed surfactant made by Tween 40/Tween 85 in 3/1 mass ratio, ca. 156 minutes for extraction time, and the liquid/solid ratio at 15. Under these conditions, according to the fitted second-order polynomial model, the response Y, the percentage of LO obtained by surfactant-enhanced hydrodistillation to that by conventional solvent extraction, was predicted to be 30.14. A pseudo-first order kinetics could simulate the extraction process well and the mass transfer coefficient of LO from rind into hydrodistillate could be improved in the presence of surfactant. The composition of LO was analyzed by both GC-FID and HPLC, indicating no trace of surfactant remained in the LO obtained by the hydrodistillation process. The solubility of LO appeared linearly increasing with surfactant concentration and showed a value higher than that of commercial lemon oil (CLO). A microemulsion formed from 0.3 wt% LO in 5 wt% surfactant solution could maintain stable for period more than 28 days. The antibacterial tests illustrated the better activity of LO against E. coli and S. aureus, even better than CLO, besides.