Journal
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
Volume 64, Issue 20, Pages 4095-4104Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jafc.6b00641
Keywords
H2S; thiols; copper; oxidation; wine aroma; reaction mechanism
Funding
- Pennsylvania Wine Marketing and Research Board
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Sulfidic off-odors as a result of hydrogen sulfide (H2S) and low-molecular-weight thiols are commonly encountered in wine production. These odors are usually removed by the process of Cu(II) fining, a process that remains poorly understood. The present study aims to elucidate the underlying mechanisms by which Cu(II) interacts with H2S and thiol compounds (RSH) under wine-like conditions. Copper complex formation was monitored along with H2S, thiol, oxygen, and acetaldehyde concentrations after the addition of Cu(II) (50 or 100 mu M) to air-saturated model wine solutions containing H2S, cysteine, 6-sulfanylhexan-1-ol, or 3-sulfanylhexan-1-ol (300 mu M each). The presence of H2S and thiols in excess to Cu(II) led to the rapid formation of similar to 1.4:1 H2S/Cu and similar to 2:1 thiol/Cu complexes, resulting in the oxidation of H2S and thiols and reduction of Cu(II) to Cu(I), which reacted with oxygen. H2S was observed to initially oxidize rather than form insoluble copper sulfide. The proposed reaction mechanisms provide insight into the extent to which H2S can be selectively removed in the presence of thiols in wine.
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