Recovery of Polyphenols from Wine Wastewaters by Membrane Operations

Grape seeds and pomace (a solid material consisting of skins and grape seeds) are typical by-products of the winemaking process containing phenolic compounds. Grape seeds contain basically (w/w) 40 % fiber, 16 % essential oil, 11 % protein, 7 % complex phenolic compounds, sugars, minerals, and other substances (Campos et al. 2008). Grape skin is a source of anthocyanidins and anthocyanins, natural pigments with antioxidant properties. These phenolic compounds have an extremely high market value as food additives, nutraceuticals, and cosmeceuticals, due to their biological activity (Crespo and Brazinha 2010). A membrane-based process scheme for the purification, fractionation, and concentration of phenolic compounds from wine wastewaters is depicted in Fig. 1. The purification step devoted to the removal of undesirable compounds (such as fats, proteins, and sugars) and microorganisms is based on the use of ultrafiltration (UF) membranes. The use of appropriate nanofiltration (NF) membranes allows for obtaining fractions enriched in phenolic compounds. The final concentration step with removal of the extracting solvent (as permeate) is performed by reverse osmosis (RO).