Polyphenol extraction from grape wastes: Solvent and pH effect

Celia M. Librán, Luis Mayor, Esperanza M. Garcia-Castello, Daniel Vidal-Brotons

Instituto Universitario de Ingeniería de Alimentos para el Desarrollo, Universitat Politécnica de València, Camino de Vera s/n, 46022 Valencia, Espa?a.

DOI: 10.4236/as.2013.49B010                

Abstract

World wine industry transforms 10% - 25% of raw grapes into residues, mainly represented by lees, grape marcs, seeds and stems. These by-products are a rich source of polyphenols and therefore they can be used to produce new added value products. The aim of this work wasto determine the best process conditions(treatment time, % of ethanol and pH of the solvent)during solid-liquid extraction of polyphenolsfrom grape marcs, by analyzing the phenolic content of the extracts, namely: total polyphenol content, flavanols, flavonols, phenolic acids and anthocyanins. Antioxidant activity of the extracts was also determined. An extraction time of two hours was enough since longer times did not increase process yields. Best extraction yields were obtained for 75% ethanol solutions. Basic pH led to better yields in extracting media with low percentage of ethanol, whereas acid pH presented better extraction yields in extracting media with high percentage of ethanol. Among all the polyphenols extracted, anthocyanins were themost abundant representing over 40% of the total. In general, the best process conditions were 2 h ofextraction in a 75% EtOH liquid mixture at pH =2.

Keywords

Antioxidants; By-Products; Fruits; Solvent Extraction; Wine

Conflicts of Interest

The authors declare no conflicts of interest.

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