Study of a new extraction process: controlled instantaneous decompression. Application to the extraction of essential oil from rosemary leaves

Experiments to extract the essential oil from rosemary (Rosmarinus officinalis L.) were carried out using a new process: 'Detente Instantanee Controlee (DIC) or controlled instantaneous decompression. This process involves subjecting the rosemary leaves for a short period of time to a steam pressure varying from 0.5 to 3 bar, followed by an instantaneous decompression to a vacuum(about 15 mbar). We have studied the effect of pressure, processing time and the number of decompressions on the extraction efficiency. The moisture content of the rosemary leaves before treatment was maintained at about 35%. Qualitative and quantitative chemical analyses were undertaken on the essential oil present in the rosemary leaves after extraction by steam distillation, and on the liquid extract. It appears that a pressure of the order of 1 bar and a treatment time of 10 minutes are sufficient to extract more than 90% of the essential oil. The effect of modifying the operating parameters on the efficiency of extraction of 10 components of the rosemary essential oil was also studied. Our results show that in the solid phase over 97% of essential oil compounds were extracted from the plant leaves after a 10 minute treatment at 3 bar. Furthermore, the efficiency of the extraction of rosemary essential oil was confirmed by scanning electron microscopy. (C) 1998 John Wiley & Sons, Ltd.