TITLE:
Polyphenol extraction from grape wastes: Solvent and pH effect
AUTHORS:
Celia M. Librán, Luis Mayor, Esperanza M. Garcia-Castello, Daniel Vidal-Brotons
KEYWORDS:
Antioxidants; By-Products; Fruits; Solvent Extraction; Wine
JOURNAL NAME:
Agricultural Sciences,
Vol.4 No.9B,
November
6,
2013
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.