Microwave-assisted Hydrodistillation for Extraction of Essential Oil from Patchouli (Pogostemon cablin) Leaves

Conventional hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) methods has been compared and evaluated for their effectiveness in the isolation of essential oils (EOs) from patchouli (Pogostemon cablin) leaves. The MAHD method offers important advantages over HD, viz. shorter extraction time (126 min vs. 417 min for HD); better yields (2.7227 % v/w vs. 2.6132 % v/w for HD); environmental impact (energy cost is appreciably higher for performing HD than that required for rapid MAHD extraction); and provides a more valuable EO (with high amounts of oxygenated compounds). It also offers the possibility for better reproduction of the natural aroma of the EO from patchouli leaves than that obtained using HD. The extraction of patchouli consisted of an initial, fast oil distillation followed by a slow oil distillation. Based on the experimental kinetic results, a semi-empirical model was fitted. The experimental investigation shows also that the operation time for MAHD in opposite to classical HD, for the same product quantity, was shorter. Higher yield results from higher extraction rates by microwave and could be due to a synergy of two transfer phenomena: mass and heat acting in the same way.