Pigment profiles of grapes and of wines

Abstract

Gel column analysis of pigment extracts has been automated, and the distribution of total coloured constituents in terms of tannin pigments, acylated anthocyanins and anthocyanins can now be measured routinely, enabling rapid evaluation of materials. Quantitative determinations of polymeric and monomeric pigments in grape extracts and in young wines have been made from the pigment elution curves. Wine grape varieties from the same viticultural area were found to have characteristieally different elution curves. Evidence Ls presented for one variety that some degree of selective extraction of pigments occurs during normal fermentation on skins, the anthocyanins being more efficently extracted than other fractions - thus the composition of pigments in the new wine differs from that in the grape. Other young varietal wines are also qualitatively different from one another in pigment compositions, which generally resemble those of the grape varieties.
Regional differences between grapes and wines oi one variety have been demonstrated, which relate to colour extraction and to the ageing characteristics of the wines from these regions.
The gross changes in pigment distribution which occur during ageing of red wines, with progressive loss of monomeric pigments and increase in the relative proportions of tannin pigments are described. The latter fraction is seen to be of primary importance to red wine technology.
The elution curves obtained are regarded as pigment profiles of the grapes or wines, and the utility of this concept in viticultural and oenological research is demonstrated.