Impact of copper residues in grape must on alcoholic fermentation: effects on yeast performance, acetaldehyde, and SO₂ production

Abstract

The aim of this work was to verify the potential effect of copper residues on alcoholic fermentation, focusing on Cu²⁺ concentrations compatible with real ranges of vineyard contamination. In fact, the goal of the trial was to compare different commercial strains of Saccharomyces cerevisiae in order to observe the effect of copper on their metabolism, in terms of fermentation kinetics, production of free and total SO₂ and production of acetaldehyde, rather than to verify at what copper concentration the fermentation goes sluggish or stuck. A second objective was also to identify the yeast strains whose behavior is less affected by the presence of copper.

For this reason, a first test was conducted on different natural white musts, contaminated or not with 10 mg/L of Cu²⁺, trying to mimic as much as possible what happens in the cellar. Fifteen active dry yeasts were compared, outlining a common effect of acetaldehyde increase due to copper presence, but displaying a high strain- and must-dependent individual behavior in terms of amounts of SO₂ and acetaldehyde produced.

To investigate the impact of Cu²⁺ on yeast metabolism under more controlled conditions, a subset of relevant strains was compared in a synthetic must, added or not with Cu²⁺. The influence of fermentation temperature was also evaluated, carrying out the experiments at 16, 18, and 20 °C. Fermentation kinetics, free and total SO₂ production, and acetaldehyde production were monitored.

The results confirm the common observation of increased acetaldehyde production in the presence of copper, while also confirming strain-specific responses, which resulted more stable than in natural must. Regarding temperature effects, beyond the expected impact on fermentation duration, the initial findings suggest that temperature influences the magnitude of the difference between copper and control conditions.

References

1. Nardi, T. Impact of copper residues in grape must on alcoholic fermentation: effects on yeast performance, acetaldehyde and SO₂ production. Recording of the presentation delivered at Enoforum Spain 2026, Zaragoza, 20–21 May 2026. Available soon on Infowine Premium: https://vinidea.it/es/brand/infowine/