WINETECH Technical Yearbook 2020

The management of phenols in the vineyard and cellar

MAY 2020

CHARL THERON: Private consultant KEYWORDS: Phenols, phenol analyses, phenol management

are also a flavonoid. Five different antho - cyanin compounds occur in red grapes, of which malvidin is the most dominant one. Both the skin tannins and anthocyanin concentrations increase after veraison of the grapes, until a stage which is known as optimal phenolic ripeness. After that the concentrations commence to decrease. The phenol concentrations can be influenced by different factors, like berry size, seed size, number of seeds and skin-pulp ratio. Phenolic analyses are mainly used for red wine making. It can however also be used for Chardonnay to differentiate between the different press fractions and sites. Phenol concentrations can however not be interpreted directly like acid or sugar concentrations, seeing that different assays are used and cultivar and origin differenc - es will also occur. Phenol concentrations

Winemakers are increasingly using phenol data of the vineyard and cellar to manage the colour and tannins in order to improve the general quality of their wines. By means of analyses and consultation more data becomes available. Phenols are chemical compounds, which are associated with phenol groups, consist- ing of six carbon benzene rings. Phenols are very reactive and can inter alia bind to proteins or other phenols. Grape phenols can be divided into non-fla - vonoids, which occur mainly in the pulp and flavonoids, which occur mainly in the seeds, but also to lesser extent in the skins and stems (flavanols) or mainly in the skins and stems (flavonols). Anthocyanins, which are responsible for the red colour of red grapes and also occur in the skins,

Skin fermentation has a great influence on the phenol concentration of wine.

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