Recovery of polyphenols from winery wastes

Abstract

Wine industry is one of the most important agro-industrial activities throughout the world. Consequently, treatment and disposal of their wastes (lees, grape marc, stalks) are critical issues in wine-producing regions, so that, in these locations, wine is produced in wide scale, generating large amount of wastes during the grape harvest and racking periods, i.e., in just 3–4 months over the year [1]. Nevertheless, winery wastes are rich in value-added compounds, the polyphenols, which have high antioxidant properties. These wastes are abundant, being a cheap and attractive source for the recovery of these natural compounds [2]. Nowadays, polyphenols are extracted using organic solvents (methanol, ethanol, ethyl acetate, etc.) which are toxic. As an alternative to the extraction with toxic solvents, commonly employed for this matter, the present study investigated a membrane-based process for the recovery of antioxidants present in wine lees from the second racking of red winemaking. By means of microfiltration associated with water dilutions (aqueous extraction), a permeate with antioxidant properties was obtained representing a recovery of more than 20% of the total content of polyphenols from the wine lees. Subsequently, the polyphenols concentration is carried out by nanofiltration.