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 off icinalis L.) were carried out using a new process: 'Detente Instantane e Controlee (DIC) or controlled instantaneous decompression. This proc ess 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 instant aneous decompression to a vacuum(about 15 mbar). We have studied the e ffect of pressure, processing time and the number of decompressions on the extraction efficiency. The moisture content of the rosemary leave s before treatment was maintained at about 35%. Qualitative and quanti tative 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 a nd a treatment time of 10 minutes are sufficient to extract more than 90% of the essential oil. The effect of modifying the operating parame ters on the efficiency of extraction of 10 components of the rosemary essential oil was also studied. Our results show that in the solid pha se over 97% of essential oil compounds were extracted from the plant l eaves after a 10 minute treatment at 3 bar. Furthermore, the efficienc y of the extraction of rosemary essential oil was confirmed by scannin g electron microscopy. (C) 1998 John Wiley & Sons, Ltd.