To better understand how the presence of different metal species can influence ageing of bottled wine and provide options to minimise detrimental influences of metals through wine production processes.
Metal ions are naturally present in grapes and wine, and are often added during the winemaking process to reduce formation of volatile sulfur compounds. Generally, the recommended total concentrations of metals in wine are given as broad ranges. This is due to the difficulty in linking concentrations to effects, probably because reactivity of the metal depends on the molecular species present, not the overall concentrations. Lack of understanding means that wine ageing and shelf life in bottle cannot be reliably predicted and addition rates are not optimal.
This project tackles the role of these different metal species and metal concentration ratios on colour and flavour development in wine. It aims to more deeply understand the consumption of sulfur dioxide by oxygen in red and white wines, why the rate varies from wine to wine and the role of metal species in this variation. The influence of ascorbic acid, a common wine additive, on the stability and activity of copper(I) sulfide, will be determined, and a link established between metal speciation and steps in the wine production process that allow efficient removal of metals from wine and juice. The most viable novel winery operations to modify the metal profile of a wine will be trialled on a typical winery scale.
The results from this project will address an increasing consumer preference for minimal winemaking intervention, reduce input costs for wineries and impact positively on wine quality through minimising the detrimental effect of metals both during fermentation and during storage in bottle.