Compositional changes in grape polyphenols throughout maturation

Abstract

Grape berries of Plavac Mali and Trnjak cv. were sampled during the period from onset of coloration to harvest. The polyphenol constituents were extracted from grape seeds. Fractionation of neutral phenolics was carried out on Sep Pak C18 cartridges. Separation and quantification of low molecular weight flavans was done using the high‐performance liquid chromatography reversed‐phase technique. The changes in composition of catechin monomers and procyanidin dimers were followed during the 1990, 1991 and 1992 seasons. The seed maturation was characterised by relative enrichment in dimeric compared to monomeric forms. The dominant monomer in grape seed extracts was (+)‐catechin for Plavac Mali cv. and ( — )‐epicatechin for Trnjak cv. The dominant procyanidin dimer was procyanidin dimer B2. The mass amounts of monomeric and dimeric forms were cultivar dependent.