A pervaporation-microfiltration-osmotic distillation hybrid process for the concentration of ethanol-water extracts of the Echinacea plant

A three-stage hybrid membrane process for the concentration of ethanol-water extracts of the Echinacea plant has been investigated. Preliminary investigations using osmotic distillation in a single-stage process resulted in severe membrane wet-out by the ethanol-soluble, sparingly water-soluble alkyl amides that precipitated from solution due to the preferential removal of ethanol. In Stage 1 of the hybrid process, ethanol removal from the neat extract was achieved by pervaporation (PV). This gave an ethanol-free aqueous product containing suspended alkyl amides that was suitable for marketing in tincture form. In Stage 2, the precipitated alkyl amides were removed from the Stage 1 product by microfiltration (MF). In Stage 3, the microfiltration permeate was concentrated several-fold by osmotic distillation, followed by adding-back of the microfiltration retentate containing the precipitated alkyl amides to the osmotic distillation retentate. This gave a highly concentrated product suitable for marketing in capsule form. In addition to process design and product characterisation, pervaporation operating conditions were optimised for greatest efficiency in this application. (C) 2002 Elsevier Science B.V. All rights reserved.