Concentration and Fractionation of Polyphenols by Membrane Operations.

BACKGROUND: This review aims to present the relevant background information and current research status in concentration of polyphenols using membrane technologies. The potential implementation of membrane separation to bioactive compounds like soluble phenolics from aqueous and organic solvent solutions is gaining increasing interest in the recent years. This review does not pretend to cover the abundant published literature on the subject, but to be representative for the observed tendencies in membrane processes applications for concentration of polyphenols derived from natural products. The first part of the article includes general information regarding the polyphenols and the traditional methods for their separation (such as: thin layer chromatography; paper chromatography; gas chromatography; high performance liquid chromatography; capillary electrophoresis), while the second part presents a review of different membrane processes applied for concentration of polyphenols. Three main sources for such implementations are discussed: (1) aqueous or organic solvent extracts from plant material, (2) fruits, and (3) recovery of polyphenols from industrial waste liquids. A diversity of membrane processes are considered in a large scope of implementations ranging from lab-scale studies to pilot and semiindustrial scale operations.

CONCLUSION: Membrane technology is an excellent candidate to make a paradigm shift in biological active compounds fractionation/separation processes. Presented results clearly demonstrate that membrane processes are of great advantages over traditionally used methods; however, characterization of separated polyphenols has to be improved. Most of citied authors concentrated their investigation only on the total amount of polyphenols determination. Exhaustive studies including: antioxidant activities, retention index, total soluble solids, or volume reduction factor, have been only carried out by a few authors.