Extraction of phenolic compounds during vinification of Pinot Noir wine examined by HPLC and cyclic voltammetry

Abstract

The phenolic profiles of four Pinot Noir fermenting musts were examined over a period of 18 days prior to barrel storage, using HPLC levels of individual polyphenols, the Folin-Ciocalteu assay and absorbance at 280 nm for total phenols, and the cyclic voltammetry response of the musts, diluted in a pH 3.6 model wine solution, for their activity as reducing agents. These methods showed the early extraction of various hydroxycinammates from the grape, followed by skin anthocyanins and flavonol glycosides, and high levels of flavan-3-ols from the seeds towards the end of the fermentation. The appearance of the individual phenolics was matched by cyclic voltammetry peaks at electrode potentials expected for each compound. Cyclic voltammetry also produced a semi-quantitative measure of the level of galloyl and catechol groups present, which correlated well with other total phenol measures.