Macrowine 2021
IVES 9 IVES Conference Series 9 Reaction Mechanisms of Copper and Iron with Hydrogen Sulfide and Thiols in Model Wine

Reaction Mechanisms of Copper and Iron with Hydrogen Sulfide and Thiols in Model Wine

Abstract

Fermentation derived sulfidic off-odors due to hydrogen sulfide (H2S) and low molecular weight thiols are commonly encountered in wine production and removed by Cu(II) fining. However, the mechanism underlying Cu(II) fining remains poorly understood, and generally results in increased Cu concentration that lead to deleterious reactions in finished wine. The present study describes a mechanistic investigation of the iron and copper mediated reaction of H2S, cysteine, 3-sulfanylhexan-1-ol, and 6-sulfanylhexan-1-ol with oxygen. The concentrations of H2S, thiols, oxygen, and acetaldehyde were monitored over time. It was found that Cu(II) was rapidly reduced by both H2S and thiols to Cu(I). The addition of Fe(III) in combination with Cu resulted in the rapid reduction of Fe(III) by Cu(I) and the resulting Fe(II) redox cycled by reacting with oxygen. Furthermore, the presence of Fe and thiols prevented the removal of H2S by precipitation as insoluble CuS promoting H2S oxidation and formation of polysulfides, effectively keeping both metals and sulfide species in wine after the copper fining process.

Publication date: May 17, 2024

Issue: Macrowine 2016

Type: Article

Authors

Gal Kreitman*, David Jeffery, John Danilewicz, Ryan Elias

*Penn State University

Contact the author

Tags

IVES Conference Series | Macrowine | Macrowine 2016

Citation

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