Chemical characterization of different granulometric fractions of grape stalks waste

The chemical composition of grape stalks wastes from wine production was investigated after milling and separation in three different size material fractions. The chemical characterization included summative composition, total polyphenols, condensed tannins, lipophilic extractives ash composition, determination of acidic functional groups and FTIR analysis. Extractives are the main components of grape stalks, especially polar extractives soluble in hot water and in 1% NaOH. The milling and separation process results in an enrichment of extractives and ash in the finest fraction and conversely, an enrichment of structural components in the largest fractions. The bands obtained by FTIR analysis confirm the presence of lignin, polysaccharides and polyphenolic compounds. The results of this research show that fractioning of grape stalks waste is a way to enrich the material in target valuable components and to improve efficiency of resource utilization. (C) 2013 Elsevier B.V. All rights reserved.