Analysis of polymeric phenolic materials separated from 22 Pinot noir wines of a single producer

Abstract

Colour and phenolic substances are important to red wine quality. This study investigated 22 New Zealand Pinot noir wines sourced from the same producer, consisting of various vintages and quality levels. Polymeric phenolic materials (PPMs) were separated from these wines by removing the monomeric anthocyanins using isoamyl alcohol. The colour properties by modified Somers assay and methylcellulose precipitable (MCP) tannins of PPMs were determined. 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 PPMs, and the degree of ionisation of these bleachable pigments increased along with wine age. Statistical analysis demonstrated the dominant effect of wine age on colour properties of PPM, and tannin concentration was mainly related to vintage.