Sensory and Chemical Characterization of Phenolic Polymers from Red Wine Obtained by Gel Permeation Chromatography

Abstract

The polyphenols of a 2005 Cabernet Sauvignon were fractionated by gel permeation chromatography. The obtained fractions were reconstituted in a model wine medium for analysis. The chemical properties of the fractions were investigated by HPLC-DAD, HPLC-ESI-MSⁿ, colorimetric analysis, and additional chemical assays. Application of these different techniques and combination with the elution pattern of the gel permeation material revealed some valuable structural information. The early eluting fractions, which were larger in molecular size and/or more polar than late eluting fractions, contained higher proportions of pigmented polymers and higher amounts of bound anthocyanins. These anthocyanins were responsible for the color properties of the early eluting fractions, which could be separated according to CIELab analysis. The later eluting fractions exhibited lighter, more yellowish color, provoked by the higher tannin concentration, and contained low molecular weight proanthocyanidins. Descriptive sensory analysis was carried out, assessing bitterness, sourness, and attributes describing different subqualities of astringency. Dry tannin intensity was rated lower for the early eluting anthocyanin-rich polymers compared to the later eluting fractions, which were rich in procyanidins and/or oligomerized flavan-3-ols. Accordingly, the attenuation of the astringent perception, as it is generally observed during red wine aging, may be attributed to increasing anthocyanin incorporation into the polymers. In contrast to astringency, the intensity of bitterness was not sufficiently correlated with any chemical parameter. This observation suggests that very specific phenolic structures are responsible for the bitter perception in red wines. As the high molecular pigmented polymers evoked lowest astringency ratings, the results of this study indicate that the increase of astringency due to higher degrees of polymerization can be substantially prevailed by the incorporation of anthocyanins into polymeric structures.