Colour properties and tannin concentrations of polymeric phenolic materials extracted from Pinot Noir wines of a single NZ producer

Abstract

Polymeric phenolic material (PPM) was separated from monomeric anthocyanins by removing the latter using isoamyl alcohol in 22 Pinot Noir wines of different vintages and grades. The colour and tannin concentrations of PPM were determined using a modified Somers assay and methylcellulose precipitation (MCP) tannin assay, respectively. With wine age increasing, the ratio of absorbance at 520 nm at pH 1.0 to that at 3.4 decreased from 2.6 to 1.1. This decreasing trend with wine age is reported for the first time in Pinot Noir wines. The presence of bleachable polymeric pigments was also observed in PPM, and the degree of ionisation of these bleachable pigments increased along with wine age. Statistical analysis demonstrated the dominant effect of age on colour properties of PPM, regardless of vintage and grade. In contrast, total phenolics and tannin concentration mainly related to vintage, rather than age.