Metal ion speciation: Understanding its role in wine development and generating a tool to minimise wine spoilage

Summary

Objectives

To develop a tool to measure metal ion reactivity in wine and predict the risk of spoilage due to oxidation, due to casse formation, due to development of H2S and other undesirable sulfur compounds.

Background

Oxidative, reductive and colloidal phenomena are recognized as major contributors to wine faults. Iron and/or copper can influence all of these, impacting oxidation and reduction reactions, casse development and the formation of sulfur containing compounds. Both iron and copper exist in a variety of forms including different redox states, and either free or bound by wine components with varying binding strengths. The agents responsible for the most efficient binding of metal ions in wine are not known nor are their reactivity and roles in wine spoilage.

The recommended total concentrations of metals in wine are given as broad ranges. This is due to the difficulty in linking concentrations to metal-induced effects, probably because reactivity depends on the species present, not the overall levels. A variety of research-orientated methods to measure metal speciation in wine have already been developed but they are yet to be applied to determine what the different species do in wine.

Research approach

This project will use current research tools that measure different forms of metal ions (metal speciation) and then relate the speciation measures to metal-induced processes in wine. The components of wine able to interact with metal ions to form inert or ‘non-active’ metal species will be identified. Speciation measures that provide a good predictor of metal activity (i.e. responsible for specific detrimental wine effects) will be developed into a more routine analytical method suitable for the wine industry.

Industry benefit

This project will develop analytical tools for winemakers to evaluate the potential of their wines to be spoilt.