Extraction of turpentine essential oil from Pinus pinaster ait: Comparison of yield and composition between conventional- or microwave assisted-hydro-distillation and vacuum distillation

Turpentine essential oil was extracted from Pinus pinaster Ait. resin, collected from "les C & eacute;vennes" area (south-eastern France). Three extraction processes were investigated: conventional hydro- distillation (CHD), microwaves assisted hydro-distillation (MWHD) under a limited amount of water and a solvent-free process, i.e. vacuum distillation (VD). The selected experimental conditions agreed with the theoretical flash region and equilibrium yield predicted by flash calculations described well the results. CHD using a low water/resin ratio of 2 showed a high yield (similar to 25%w/w) similar to 25%w/w) and a turpentine essential oil (EO) primarily rich in alpha- and beta pinenes, but also in sesquiterpene compounds such as beta caryophyllene. Microwave heating did not improve the total extraction staying around 20%w/w but depending on power condition, both the monoterpene/sesquiterpene ratio and the proportion of oxygenated compounds can be increased. Pressure, rather than temperature, was observed to have a greater impact on the VD extraction yield. At a temperature above or equal to 90 degrees C and a pressure of 1 kPa, the yield became comparable to that obtained by CHD but with a high pinenes and low sesquiterpenes content.