Copper-Complexed Hydrogen Sulfide in Wine: Measurement by Gas Detection Tubes and Comparison of Release Approaches

Chen, Yi; Jastrzembski, Jillian A.; Sacks, Gavin L.

doi:10.5344/ajev.2016.16024

Cited by 15 publications

(45 citation statements)

References 28 publications

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“…The AR-aging assays hardly differentiate between 2 and 3, because reduction and desulfhydration can take place simultaneously during AR-aging. A fine assignment will require the use of chemical reducing agents, such as TCEP, 19,22 after demonstrating that they not promote desulfhydration, and/or specific HPLC-MS strategies devoted to measure oxidized precursors. 22 Leaving aside the catalytic systems able to induce "de novo" formation, it can be considered that each wine contains a fixed pool of H 2 S and MeSH, which will be referred as the "present total amount" of these molecules, distributed into three differentiable fractions: free; metal bound; and oxidized precursors.…”

Section: Mesh Productionmentioning

confidence: 99%

Elusive Chemistry of Hydrogen Sulfide and Mercaptans in Wine

Ferreira

Franco‐Luesma

Vela

2017

J. Agric. Food Chem.

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This paper summarizes, discusses, and complements recent findings about the fate of HS and methanethiol (MeSH) during wine storage. Analytical assays to determine free volatile sulfur compounds (VSCs) and brine-releasable (BR-) VSCs in combination with accelerated reductive (AR) aging and micro-oxygenation (MOX) assays allow characterizing the different categories of species able to produce HS and MeSH and the processes of interconversion. Each wine seems to contain a specific total amount of HS and MeSH distributed into free, metal-complexed, and oxidized forms (di and polysulfides) interconnected through reversible redox equilibria whose external expression is wine redox potential. Oxidation transforms all mercaptans likely into nonvolatile disulfides and hydrodisulfides. In anoxia, these molecules are spontaneously and quantitatively reduced back. The concomitant accumulation of major wine thiols would provoke complex dissociation and the release of free HS and MeSH. Additionally, total amounts can increase due to the metal-catalyzed desulfhydration of cysteine and methionine.

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Section: Mesh Productionmentioning

confidence: 99%

Elusive Chemistry of Hydrogen Sulfide and Mercaptans in Wine

Ferreira

Franco‐Luesma

Vela

2017

J. Agric. Food Chem.

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“…Upon oxidation in the presence of iron, most H 2 S and mercaptans would end as polysulfides and other complex species (Kreitman, Danilewicz, Jeffery, & Elias, 2016b). Nevertheless, some of the complexes formed between Cu(II) and other metal cations with H 2 S and MeSH have been found to be reversible (Chen, Jastrzembski, & Sacks, 2017;Franco-Luesma & Ferreira, 2014), so that a simple dilution of wine in brine makes it possible to recover the volatile species. Dilution in general favors dissociation of complex forms, the increase of ionic strength reduces solubility of neutral forms and hence promotes volatility and the presence of chloride ions may further complex Cu(I) and even Zn(II).…”

Section: Introductionmentioning

confidence: 99%

The effects of copper fining on the wine content in sulfur off-odors and on their evolution during accelerated anoxic storage

2017

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Three different red wines with reductive character have been treated with two different doses of copper sulfate (0.06 and 0.5mg/L) and with a commercial copper-containing product at the recommended dose (0.6mg/L). Wines were in contact with copper one week, centrifuged and stored at 50°C in strict anoxia for 2weeks (up to 7 in one case). Brine-releasable (BR-) and free fractions of Volatile Sulfur Compounds were determined throughout the process. Relevant increases of BR-HS suggest that those wines contained other HS precursors non-detectable by the brine dilution method. Copper treatments had two major effects: 1) immediate decrease the levels of free HS and methanethiol (MeSH); 2) slow the rate at which free HS (not MeSH) increases during anoxic storage. After 7weeks of anoxia levels of free HS and MeSH were high and similar regardless of the copper treatment. Higher copper doses could induce the accumulation of BR-HS.

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“…Surprisingly, even though TCEP was much less effective than brine at releasing H 2 S from copper sulfide complexes in the recovery experiments, higher concentrations of H 2 S released by TCEP were observed in six of the seven wines (up to 25.3 µg/L). These results suggest the presence of additional TCEP-releasable sources (polythionates) of H 2 S (or thiol interferences) in wine [48]. Since TCEP acts specifically to break -S-S-bonds, polythionates will also be attacked with the release of H 2 S. (8) Elemental sulfur pesticide residues on grapes can not only produce H 2 S during fermentation, but are also able to form precursors capable of generating additional H 2 S after bottle storage.…”

Section: Discussion Of Polydithionates: the Answer To Some Unsolved Qmentioning

confidence: 87%

“…Grape juice usually contains plenty of sulfate (~160-700 mg L −1 ), but very low concentrations of cysteine and methionine (<20 mg L −1 ), and therefore, the SAP is triggered during alcoholic fermentation to support yeast growth [5,46]. The mechanisms by which H 2 S is released from the SAP are well studied and reviewed [5,[47][48][49].…”

Section: Polythionates In Wine As Precursorsmentioning

confidence: 99%

Recent Developments on the Origin and Nature of Reductive Sulfurous Off-Odours in Wine

Müller¹,

Rauhut

2018

Fermentation

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Reductive sulfurous off-odors are still one of the main reasons for rejecting wines by consumers. In 2008 at the International Wine Challenge in London, approximately 6% of the more than 10,000 wines presented were described as faulty. Twenty-eight percent were described as faulty because they presented “reduced characters” similar to those presented by “cork taint” and in nearly the same portion. Reductive off-odors are caused by low volatile sulfurous compounds. Their origin may be traced back to the metabolism of the microorganisms (yeasts and lactic acid bacteria) involved in the fermentation steps during wine making, often followed by chemical conversions. The main source of volatile sulfur compounds (VSCs) are precursors from the sulfate assimilation pathway (SAP, sometimes named as the “sulfate reduction pathway” SRP), used by yeast to assimilate sulfur from the environment and incorporate it into the essential sulfur-containing amino acids methionine and cysteine. Reductive off-odors became of increasing interest within the last few years, and the method to remove them by treatment with copper (II) salts (sulfate or citrate) is more and more questioned: The effectiveness is doubted, and after prolonged bottle storage, they reappear quite often. Numerous reports within the last few years and an ongoing flood of publications dealing with this matter reflect the importance of this problem. In a recent detailed review, almost all relevant aspects were discussed on a scientific data basis, and a “decision tree” was formulated to support winemakers handling this problem. Since we are dealing with a very complicated matter with a multitude of black spots still remaining, these advices can only be realized using specific equipment and special chemicals, not necessarily found in small wineries. The main problem in dealing with sulfurous compounds arises from the high variability of their reactivities. Sulfur is a metalloid with a large valence span across eight electron transformations from S (−II) up to S (+VI). This allows it to participate in an array of oxidation, reduction and disproportionation reactions, both abiotic and linked to microbial metabolism. In addition, sulfur is the element with the most allotropes and a high tendency to form chains and rings, with different stabilities of defined species and a high interconvertibility among each other. We suppose, there is simply a lack of knowledge of what is transferred during filling into bottles after fermentation and fining procedures. The treatment with copper (II) salts to remove sulfurous off-odors before filling rather increases instead of solving the problem. This paper picks up the abundant knowledge from recent literature and tries to add some aspects and observations, based on the assumption that the formation of polythionates, hitherto not taken into consideration, may explain some of the mystery of the re-appearance of reductive off-odors.

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Copper-Complexed Hydrogen Sulfide in Wine: Measurement by Gas Detection Tubes and Comparison of Release Approaches

Cited by 15 publications

References 28 publications

Elusive Chemistry of Hydrogen Sulfide and Mercaptans in Wine

Elusive Chemistry of Hydrogen Sulfide and Mercaptans in Wine

The effects of copper fining on the wine content in sulfur off-odors and on their evolution during accelerated anoxic storage

Recent Developments on the Origin and Nature of Reductive Sulfurous Off-Odours in Wine

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