12,538
edits
Hydrogen sulfide: Difference between revisions
m
no edit summary
Tags: Mobile edit Mobile web edit |
mNo edit summary |
||
| (14 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
[[Category:off flavors]][[Category: | [[Category:off flavors]] [[Category:brewing chemistry]] | ||
[[File:1024px-Tavurvur volcano edit.jpg|thumb|Volcanic gas]] | [[File:1024px-Tavurvur volcano edit.jpg|thumb|Volcanic gas]] | ||
Hydrogen sulfide (H<sub>2</sub>S), or just "sulfide" is a microbe-derived off flavor. It is the most common of a group of fermentation products known as volatile sulfur compounds (VSCs). Sulfide aroma and flavor is often described as sulfurous like rotten eggs, "rhino farts", sewer, or volcanic gas. It is also sometimes called a "[[reductive]]" aroma because it is more likely to accumulate under low-oxygen conditions.<ref name="Jastrzembski"/> | Hydrogen sulfide (H<sub>2</sub>S), or just "sulfide" is a microbe-derived off flavor. It is the most common of a group of fermentation products known as volatile sulfur compounds (VSCs). Sulfide aroma and flavor is often described as sulfurous like rotten eggs, "rhino farts", sewer, or volcanic gas. It is also sometimes called a "[[reductive]]" aroma because it is more likely to accumulate under low-oxygen conditions.<ref name="Jastrzembski"/> | ||
| Line 37: | Line 37: | ||
For wine and beer: | For wine and beer: | ||
* '''Sulfite''' - | * '''Sulfite''' - The presence of [[sulfite]] at the beginning of fermentation has been shown to cause formation of H<sub>2</sub>S.<ref name=Hallinan/><ref name=Jiranek/><ref name=Jiranek2002/><ref>[https://brewbrothers.freeforums.net/thread/682/biab-deoxygenated-strike-water BIAB and deoxygenated strike water.] The Biergarten website. April 2022. Accessed April 5, 2022.</ref> Brewers that use sulfite in the wort (i.e. [[low oxygen brewing|low oxygen brewers]]) need to adequately aerate/oxygenate the wort to neutralize the residual sulfite when pitching. For wine stabilization, it is recommended to wait at least two weeks before adding sulfite after fermentation ends, particularly when the yeast is still present.<ref name=Enartis>[https://www.enartis.com/wp-content/uploads/2019/12/Prevention-and-Treatment-of-Reductive-Aromas.pdf Prevention and treatment of reductive aromas.] Enartis News. Accessed March 2020.</ref> Because there is such a high risk of H<sub>2</sub>S production when adding sulfite soon after fermentation completes, we do not recommend adding sulfite to beer. | ||
* '''Aeration''' - Adding oxygen before pitching yeast is especially important in affecting nitrogen utilization and fermentation vigor, which increases the amount of sulfide stripping from the wine or beer.<ref name= | * '''Aeration''' - Adding oxygen before pitching yeast is especially important in affecting nitrogen utilization and fermentation vigor, which increases the amount of sulfide stripping from the wine or beer.<ref name=Jiranek/><ref name=Jiranek2002/> In wine production, aerating during fermentation is also helpful.<ref>Bekker MZ, Day MP, Holt H, Wilkes E, Smith PA. [https://onlinelibrary.wiley.com/doi/abs/10.1111/ajgw.12172 Effect of oxygen exposure during fermentation on volatile sulfur compounds in Shiraz wine and a comparison of strategies for remediation of reductive character.] ''Aust J Grape Wine Res.'' 2016;22(1):24–35.</ref> (See [[Aeration]]) | ||
* '''Vitamins''' - Vitamins should be supplemented | * '''Vitamins''' - Vitamins should be supplemented in wine. Supplementation is not strictly necessary in beer production since [[wort]] typically contains adequate vitamins,<ref>Briggs DE, Hough JS, Stevens R, Young TW. [https://books.google.com/books?id=bHuCdG5VSmUC&pg=PA92&lpg=PA92&source=bl&ots=8c_VpU3Fs4&sig=ACfU3U1fgQ3aPJpEANWLRXjbv580IWc1Zw&hl=en&sa=X&ved=2ahUKEwiq96Ouqp_oAhUGVa0KHf3bDJoQ6AEwA3oECAcQAQ#v=onepage&f=false ''Malting and Brewing Science: Malt and Sweet Wort.''] 2nd ed. Kluwer Academic Plenum Publishers; 1981:92.</ref><ref name=fix/><ref name=bsp>Briggs DE, Boulton CA, Brookes PA, Stevens R. [[Library|''Brewing Science and Practice.'']] Woodhead Publishing Limited and CRC Press LLC; 2004.</ref> although it is potentially helpful. Deficiencies of [[pantothenic acid]] and [[pyridoxine]] (co-factors to SRS enzymes) may cause overproduction of H<sub>2</sub>S — even when adequate [[nitrogen]] is present.<ref name=Jiranek/><ref name=Jiranek2002/><ref name=Wang>Wang XD, Bohlscheid JC, Edwards CG. [https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2003.01827.x Fermentative activity and production of volatile compounds by ''Saccharomyces'' grown in synthetic grape juice media deficient in assimilable nitrogen and/or pantothenic acid.] ''J Appl Microbiol.'' 2003;94(3):349–359.</ref><ref name="Tokuyama">Tokuyama T, Kuraishi H, Aida K, Uemura T. [https://www.jstage.jst.go.jp/article/jgam1955/19/6/19_6_439/_pdf Hydrogen sulfide evolution due to pantothenic acid deficiency in the yeast requiring this vitamin, with special reference to the effect of adenosine triphosphate on yeast cysteine desulfhydrase.] ''J Gen Appl Microbiol.'' 1973;19:439–466.</ref><ref name="Bohlscheid"/> (See [[yeast#Nutrition|Yeast Nutrition]]) | ||
* '''Nitrogen''' - Supplementing [[yeast-assimilable nitrogen]] (YAN) can help lower sulfide production, but only when there are also adequate co-factors (vitamins) present for the SRS.<ref name="Jiranek"/><ref name="Park">Park SK, Boulton RB, Noble AC. [https://www.ajevonline.org/content/51/2/91.short Formation of hydrogen sulfide and glutathione during fermentation of white grape musts.] ''Am J Enol Vitic.'' 2000;51(2):91–97.</ref> Otherwise nitrogen supplementation may ''increase'' sulfide production.<ref name="Bohlscheid"/><ref name="Wang"/><ref>Kumar GR, Ramakrishnan V, Bisson LF. [https://www.ajevonline.org/content/61/3/365.short Survey of hydrogen sulfide production in wine strains of ''Saccharomyces cerevisiae''.] ''Am J Enol Vitic.'' 2010;61(3):365–371.</ref><ref name="Butzke"/><ref name="Ugliano">Ugliano M, Kolouchova R, Henschke PA. [https://link.springer.com/article/10.1007/s10295-010-0786-6 Occurrence of hydrogen sulfide in wine and in fermentation: influence of yeast strain and supplementation of yeast available nitrogen.] ''J Ind Microbiol Biotechnol.'' 2011;38:423–429.</ref><ref name="UglianoM"/> There may also be some variability among yeast strains or species with regard to whether increasing nitrogen decreases sulfide formation.<ref name="UglianoM"/><ref>Mendes-Ferreira A, Mendes-Faia A, Leão C. [https://www.researchgate.net/publication/11282471_Survey_of_Hydrogen_Sulphide_Production_by_Wine_Yeasts Survey of hydrogen sulphide production by wine yeasts.] ''J Food Prot.'' 2002;65(6):1033–1037.</ref> Similar to vitamins, nitrogen supplementation in [[wort]] or beer is not always required, but still may be helpful under certain conditions.<ref name="Duan">Duan WD, Roddick FA, Higgins VJ, Rogers PJ. [https://www.researchgate.net/publication/281600914_A_Parallel_Analysis_of_H2S_and_SO2_Formation_by_Brewing_Yeast_in_Response_to_Sulfur-Containing_Amino_Acids_and_Ammonium_Ions A parallel analysis of H2S and SO2 formation by brewing yeast in response to sulfur-containing amino acids and ammonium ions.] ''J Am Soc Brew Chem.'' 2004;62(1):35–41.</ref><ref name="Ferreira">Ferreira IM, Guido LF. [https://www.mdpi.com/2311-5637/4/2/23/pdf Impact of wort amino acids on beer flavour: a review.] ''Fermentation (Basel).'' 2018;4(23).</ref> (See [[yeast#Nutrition|Yeast]]) | * '''Nitrogen''' - Supplementing [[yeast-assimilable nitrogen]] (YAN) can help lower sulfide production, but only when there are also adequate co-factors (vitamins) present for the SRS.<ref name="Jiranek"/><ref name="Park">Park SK, Boulton RB, Noble AC. [https://www.ajevonline.org/content/51/2/91.short Formation of hydrogen sulfide and glutathione during fermentation of white grape musts.] ''Am J Enol Vitic.'' 2000;51(2):91–97.</ref> Otherwise nitrogen supplementation may ''increase'' sulfide production.<ref name="Bohlscheid"/><ref name="Wang"/><ref>Kumar GR, Ramakrishnan V, Bisson LF. [https://www.ajevonline.org/content/61/3/365.short Survey of hydrogen sulfide production in wine strains of ''Saccharomyces cerevisiae''.] ''Am J Enol Vitic.'' 2010;61(3):365–371.</ref><ref name="Butzke"/><ref name="Ugliano">Ugliano M, Kolouchova R, Henschke PA. [https://link.springer.com/article/10.1007/s10295-010-0786-6 Occurrence of hydrogen sulfide in wine and in fermentation: influence of yeast strain and supplementation of yeast available nitrogen.] ''J Ind Microbiol Biotechnol.'' 2011;38:423–429.</ref><ref name="UglianoM"/> There may also be some variability among yeast strains or species with regard to whether increasing nitrogen decreases sulfide formation.<ref name="UglianoM"/><ref>Mendes-Ferreira A, Mendes-Faia A, Leão C. [https://www.researchgate.net/publication/11282471_Survey_of_Hydrogen_Sulphide_Production_by_Wine_Yeasts Survey of hydrogen sulphide production by wine yeasts.] ''J Food Prot.'' 2002;65(6):1033–1037.</ref> Similar to vitamins, nitrogen supplementation in [[wort]] or beer is not always required, but still may be helpful under certain conditions.<ref name="Duan">Duan WD, Roddick FA, Higgins VJ, Rogers PJ. [https://www.researchgate.net/publication/281600914_A_Parallel_Analysis_of_H2S_and_SO2_Formation_by_Brewing_Yeast_in_Response_to_Sulfur-Containing_Amino_Acids_and_Ammonium_Ions A parallel analysis of H2S and SO2 formation by brewing yeast in response to sulfur-containing amino acids and ammonium ions.] ''J Am Soc Brew Chem.'' 2004;62(1):35–41.</ref><ref name="Ferreira">Ferreira IM, Guido LF. [https://www.mdpi.com/2311-5637/4/2/23/pdf Impact of wort amino acids on beer flavour: a review.] ''Fermentation (Basel).'' 2018;4(23).</ref> (See [[yeast#Nutrition|Yeast]]) | ||
* '''Yeast strain''' - Low sulfide-producing and/or low nitrogen-requirement yeast strains may be considered.<ref name="Jiranek2002"/> | * '''Yeast strain''' - Low sulfide-producing and/or low nitrogen-requirement yeast strains may be considered.<ref name="Jiranek2002"/> Unfortunately it is not very well known which strains are high or low producers of H<sub>2</sub>S. Scott Labs and Renaissance Yeast have both bred some wine yeast strains specifically to reduce sulfide production.<ref>[https://scottlab.com/h2s-production Understanding the production of hydrogen sulfide (H<sub>2</sub>S) during fermentation.] Scott Laboratories. Accessed March 2020.</ref><ref>[https://www.thebeveragepeople.com/products/yeast/10-g-fresco-cider-wine-yeast.html 10 g fresco cider yeast - H2S preventing.] The Beverage People. Accessed March 2020.</ref> | ||
* '''Pitch rate and yeast health''' - Pitch healthy yeast at a good pitch rate to decrease nutrient demand.<ref name="Ferreira"/><ref name="Zoecklein"/> "Shocking" the yeast (rapid changes in growth conditions like temperature or [[pH]]) should be avoided.<ref name="Jiranek2002"/><ref name="OsborneJ">Osborne JP. [https://owri.oregonstate.edu/sites/agsci/files/owri/05_vitnewsletteroct07webversion.pdf Sulfides and mercaptans in wine.] Oregon State University Wine and Grape Research and Extension Newsletter. Published October 2007.</ref> Significant over-pitching may also cause excessive sulfide.<ref name="fart"/><ref name=fix/> Even re-pitching yeast may cause increased production of sulfide.<ref>Thorne RSW. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1968.tb03167.x Some observations on yeast mutation during continuous fermentation.] ''J Inst Brew.'' 1968;74:516–524.</ref> (See [[Yeast]]) | * '''Pitch rate and yeast health''' - Pitch healthy yeast at a good pitch rate to decrease nutrient demand.<ref name="Ferreira"/><ref name="Zoecklein"/> "Shocking" the yeast (rapid changes in growth conditions like temperature or [[pH]]) should be avoided.<ref name="Jiranek2002"/><ref name="OsborneJ">Osborne JP. [https://owri.oregonstate.edu/sites/agsci/files/owri/05_vitnewsletteroct07webversion.pdf Sulfides and mercaptans in wine.] Oregon State University Wine and Grape Research and Extension Newsletter. Published October 2007.</ref> Significant over-pitching may also cause excessive sulfide.<ref name="fart"/><ref name=fix/> Even re-pitching yeast may cause increased production of sulfide.<ref>Thorne RSW. [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1968.tb03167.x Some observations on yeast mutation during continuous fermentation.] ''J Inst Brew.'' 1968;74:516–524.</ref> (See [[Yeast]]) | ||
* '''Fermentation temperature''' - Generally lower temperatures decrease sulfide liberation, although not necessarily because of decreased production.<ref name="Bohlscheid">Bohlscheid JC, Osborne JP, Ross CF, Edwards CG. [https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1745-4557.2010.00365.x Interactive effects of selected nutrients and fermentation temperature on H<sub>2</sub>S production by wine strains of ''Saccharomyces''.] ''J Food Qual.'' 2011;34:51–55.</ref> However each strain has an optimum fermentation temperature to minimize its production, so lower temperature doesn't always mean lower sulfide production.<ref name="Kim">Kim YR, Moon ST, Park SK. [http://ocean.kisti.re.kr/downfile/volume/ksfst1/SPGHB5/2008/v40n2/SPGHB5_2008_v40n2_238.pdf Effects of yeast strains and fermentation temperatures in production of hydrogen sulfide during beer fermentation.] ''Korean J Food Sci Technol.'' 2008;40(2):238–242.</ref> The fermentation temperature should be controlled within the suggested range of the yeast. (See [[Temperature control]]) | * '''Fermentation temperature''' - Generally lower temperatures decrease sulfide liberation, although not necessarily because of decreased production.<ref name="Bohlscheid">Bohlscheid JC, Osborne JP, Ross CF, Edwards CG. [https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1745-4557.2010.00365.x Interactive effects of selected nutrients and fermentation temperature on H<sub>2</sub>S production by wine strains of ''Saccharomyces''.] ''J Food Qual.'' 2011;34:51–55.</ref> However each strain has an optimum fermentation temperature to minimize its production, so lower temperature doesn't always mean lower sulfide production.<ref name="Kim">Kim YR, Moon ST, Park SK. [http://ocean.kisti.re.kr/downfile/volume/ksfst1/SPGHB5/2008/v40n2/SPGHB5_2008_v40n2_238.pdf Effects of yeast strains and fermentation temperatures in production of hydrogen sulfide during beer fermentation.] ''Korean J Food Sci Technol.'' 2008;40(2):238–242.</ref> The fermentation temperature should be controlled within the suggested range of the yeast. (See [[Temperature control]]) | ||
| Line 59: | Line 59: | ||
* A small syringe or pipette to measure 1 mL volumes | * A small syringe or pipette to measure 1 mL volumes | ||
* Plastic wrap or watch glasses | * Plastic wrap or watch glasses | ||
* 1% [[Copper sulfate]] (CuSO<sub>4</sub>) solution (If you can't obtain copper sulfate, you can clean several pennies in an acid solution like lemon juice or vinegar.<ref name="Kaiser"/>) | * 1% [[Copper sulfate]] (CuSO<sub>4</sub>) solution (If you can't obtain copper sulfate, you can clean several U.S. pennies in an acid solution like lemon juice or vinegar.<ref name="Kaiser"/>) | ||
* Optional: [[Ascorbic acid]] and distilled water to make a 5% ascorbic acid solution. Mix 2.5 g ascorbic acid into 50 mL water. | * Optional: [[Ascorbic acid]] and distilled water to make a 5% ascorbic acid solution. Mix 2.5 g ascorbic acid into 50 mL water. | ||
'''Procedure:'''<ref name="morewine">[https://www.morebeer.com/images/file.php?file_id=1309 | '''Procedure:'''<ref name="morewine">[https://www.morebeer.com/images/file.php?file_id=1309 Copper sulfate trials.] MoreWine! Accessed April 2020.</ref><ref name="Gardner"/><ref>[https://www.awri.com.au/industry_support/winemaking_resources/sensory_assessment/diagnostic_test/ Diagnostic test for reductive wine characters (Cu/Cd test).] The Australian Wine Research Institute (AWRI). Accessed April 2020.</ref><br /> | ||
# Obtain two 50mL samples of wine in glasses. Label one "Control" and the other "Copper". | # Obtain two 50mL samples of wine in glasses. Label one "Control" and the other "Copper". | ||
# To the glass marked "Copper", add 1 mL of the copper sulfate solution (approx 50 ppm - this is a strong excess of copper), or pennies. | # To the glass marked "Copper", add 1 mL of the copper sulfate solution (approx 50 ppm - this is a strong excess of copper), or pennies. | ||
| Line 86: | Line 86: | ||
===Sparging with inert gas=== | ===Sparging with inert gas=== | ||
Hydrogen sulfide is highly volatile. If you have the appropriate equipment, it can be removed through "sparging" with inert gas (such as nitrogen or carbon dioxide). In other words, bubbling gas through the beer/wine/etc will carry off the hydrogen sulfide along with it.<ref name="Jastrzembski"/><ref name="Off"/><ref name="fart">[https://discussions.probrewer.com/showthread.php?49714-Fart-Smell "Fart Smell."] ProBrewer Message Board. | Hydrogen sulfide is highly volatile. If you have the appropriate equipment, it can be removed through "sparging" with inert gas (such as nitrogen or carbon dioxide). In other words, bubbling gas through the beer/wine/etc will carry off the hydrogen sulfide along with it.<ref name="Jastrzembski"/><ref name="Off"/><ref name="fart">[https://discussions.probrewer.com/showthread.php?49714-Fart-Smell "Fart Smell."] ProBrewer Message Board. Published 2015–2016.</ref><ref name="Enartis"/> | ||
Perform this method only in a well-ventilated space. The specifics of a gas sparging setup are beyond the scope of this article, but you will need a gas cylinder, an appropriate regulator, gas tubing, and an "oxygen stone". | Perform this method only in a well-ventilated space. The specifics of a gas sparging setup are beyond the scope of this article, but you will need a gas cylinder, an appropriate regulator, gas tubing, and an "oxygen stone". | ||
| Line 95: | Line 95: | ||
Hydrogen sulfide is easily oxidized to elemental sulfur, which is insoluble and flavorless. If fermentation is still active, stirring it may help volatilize and/or gently remove sulfide with low risk of also oxidizing desirable compounds. If fermentation has completed, you can simply leave the beer/wine/etc in the fermenter and oxygen that enters the vessel will react with hydrogen sulfide.<ref name="Jastrzembski"/><ref name="Kaiser"/><ref name="Osborne"/><ref name="Enartis"/> [[Aeration]] (e.g. through splash [[racking]]) may also be used, particularly in wine with [[sulfite]]. | Hydrogen sulfide is easily oxidized to elemental sulfur, which is insoluble and flavorless. If fermentation is still active, stirring it may help volatilize and/or gently remove sulfide with low risk of also oxidizing desirable compounds. If fermentation has completed, you can simply leave the beer/wine/etc in the fermenter and oxygen that enters the vessel will react with hydrogen sulfide.<ref name="Jastrzembski"/><ref name="Kaiser"/><ref name="Osborne"/><ref name="Enartis"/> [[Aeration]] (e.g. through splash [[racking]]) may also be used, particularly in wine with [[sulfite]]. | ||
Oxygen exposure does not remove mercaptans or disulfides. Furthermore, most sources suggest that aeration adds a danger of forming mercaptans and/or converting mercaptans to disulfides.<ref name="Mansfield"/><ref name="awri"/> The disulfides have a higher taste threshold so they may seem to disappear, but they can potentially change back to mercaptans later under low-oxygen conditions such as a wine with sulfite.<ref name="Zoecklein2">Zoecklein | Oxygen exposure does not remove mercaptans or disulfides. Furthermore, most sources suggest that aeration adds a danger of forming mercaptans and/or converting mercaptans to disulfides.<ref name="Mansfield"/><ref name="awri"/> The disulfides have a higher taste threshold so they may seem to disappear, but they can potentially change back to mercaptans later under low-oxygen conditions such as a wine with sulfite.<ref name="Zoecklein2">Zoecklein B. [https://www.apps.fst.vt.edu/extension/enology/downloads/SLOFactorsFinal.pdf Factors impacting volatile sulfur-like off aromas in wine and winery options.] Wine/Enology Grape Chemistry Group at Virginia Tech. Published July 2007.</ref><ref name="Elusive">Ferreira V, Franco-Luesma E, Vela E, López R, Hernández-Orte P. [https://pubs.acs.org/doi/abs/10.1021/acs.jafc.7b02427 Elusive chemistry of hydrogen sulfide and mercaptans in wine.] ''J Agric Food Chem.'' 2018;66(10):2237–2246.</ref><ref name="Vela"/> This phenomenon does not occur in beer because beer always becomes increasingly oxidized over time. | ||
Oxygen exposure (including aging without the anti-oxidant protection of sulfite) can cause [[oxidation]] of desirable compounds, which negatively affects flavor. | Oxygen exposure (including aging without the anti-oxidant protection of sulfite) can cause [[oxidation]] of desirable compounds, which negatively affects flavor. | ||
===Copper=== | ===Copper=== | ||
[[Copper]] is a common tool used for the removal of both hydrogen sulfide and mercaptans.<ref name="Osborne"/><ref name="Kaiser"/><ref name="Off"/> Copper binds to these sulfur compounds to form odorless complexes, which precipitate to some degree.<ref name="Off"/><ref name="Muller"/> When copper is used in combination with [[ascorbic acid]] and [[sulfite]], disulfides can be removed as well (see below). Adding copper is fairly easy and inexpensive. Copper fining works in both wine and beer.<ref>Walker | [[Copper]] is a common tool used for the removal of both hydrogen sulfide and mercaptans.<ref name="Osborne"/><ref name="Kaiser"/><ref name="Off"/> Copper binds to these sulfur compounds to form odorless complexes, which precipitate to some degree.<ref name="Off"/><ref name="Muller"/> When copper is used in combination with [[ascorbic acid]] and [[sulfite]], disulfides can be removed as well (see below). Adding copper is fairly easy and inexpensive. Copper fining works in both wine and beer.<ref>Walker MD. [https://onlinelibrary.wiley.com/doi/abs/10.1002/jsfa.2740670105 The influence of metal ions on concentrations of flavour-active sulphur compounds measured in beer using dynamic headspace sampling.] ''J Sci Food Agric.'' 1995;67(1):25–28.</ref> | ||
Copper should not be added until the fermentation is complete and the amount of yeast material is reduced by racking. This is because yeast cells can bind with copper and reduce effectiveness, and because addition of copper during fermentation may promote sulfide production by yeast.<ref name="Osborne"/> However some yeast may be helpful for removing the excess copper.<ref>Viviers, M | Copper should not be added until the fermentation is complete and the amount of yeast material is reduced by racking. This is because yeast cells can bind with copper and reduce effectiveness, and because addition of copper during fermentation may promote sulfide production by yeast.<ref name="Osborne"/> However some yeast may be helpful for removing the excess copper.<ref>Viviers M, Smith M, Wilkes E, Smith P, Johnson D. [https://winesvinesanalytics.com/features/article/132047/Role-of-trace-metals-in-wine-reduction Role of trace metals in wine 'reduction'.] ''Wines & Vines.'' 2014;May.</ref> The beer/wine should be left undisturbed for several days after treatment so the copper sulfide (a very fine black powder) can settle to the bottom of the container. Then it should be carefully racked off the residue.<ref>[http://www.thevintnervault.com/index.php?p=w_m_tips&id=5781 Removing H2S (hydrogen sulfide).] The Vintner's Vault. Accessed March 2020.</ref><ref name="Gardner"/><ref name="Osborne"/> | ||
Despite its widespread use, copper usage has a lot of potential disadvantages. The copper-sulfide complexes are challenging to remove from wine/beer, and they can potentially release the sulfide or mercaptans later.<ref name="Huang"/><ref name="Clark"/><ref>Ugliano, | Despite its widespread use, copper usage has a lot of potential disadvantages. The copper-sulfide complexes are challenging to remove from wine/beer, and they can potentially release the sulfide or mercaptans later.<ref name="Huang"/><ref name="Clark"/><ref>Ugliano M, Kwiatkowski M, Vidal S, et al. [https://pubs.acs.org/doi/abs/10.1021/jf1043585 Evolution of 3-mercaptohexanol, hydrogen sulfide, and methyl mercaptan during bottle storage of Sauvignon blanc wines. effect of glutathione, copper, oxygen exposure, and closure-derived oxygen.] ''J Agric Food Chem.'' 2011;59(6):2564–2572.</ref><ref>Viviers MZ, Smith ME, Wilkes E, Smith P. [https://pubs.acs.org/doi/abs/10.1021/jf403422x Effects of five metals on the evolution of hydrogen sulfide, methanethiol, and dimethyl sulfide during anaerobic storage of Chardonnay and Shiraz wines.] ''J Agric Food Chem.'' 2013;61(50):12385–12396.</ref><ref>Bekker MZ, Kreitman GY, Jeffery DW, Danilewicz JC. [https://pubs.acs.org/doi/abs/10.1021/acs.jafc.8b04690 Liberation of hydrogen sulfide from dicysteinyl polysulfanes in model wine."] ''J Agric Food Chem.'' 2018;66(51):13483–13491.</ref><ref name="Muller"/> Copper might catalyze the release of sulfide from sulfur-containing amino acids.<ref name="Jastrzembski"/> Copper also reacts with any other thiols in the beer/wine. Therefore, if you are dealing with a wine variety rich in aromatic varietal thiols (e.g., Sauvignon blanc, rosés, and to a lesser extent Riesling and Gewürztraminer), the addition of copper can reduce the wine's varietal aroma.<ref>Gardner D. [https://www.dgwinemaking.com/wine-flaw-focus-hydrogen-sulfide-and-reduction/ Wine flaw focus: hydrogen sulfide and "reduction".] Denise Gardner Winemaking. Published October 19, 2018. Accessed March 2020.</ref><ref name="Mansfield"/> In beer, thiol-containing hop compounds may be affected. Too much copper can cause a haze, referred to as "copper casse".<ref name="Mansfield"/><ref name="Muller"/> Risk of haze formation is greatly increased if copper is added immediately prior to packaging, without allowing adequate time for the beer/wine to stabilize during bulk storage. Lastly, excess copper catalyzes oxidation reactions, which can accelerate staling.<ref name="Mansfield"/><ref>Clark AC, Wilkes EN, Scollary GR. [https://onlinelibrary.wiley.com/doi/abs/10.1111/ajgw.12159 Chemistry of copper in white wine: a review.] ''Aust J Grape Wine Res.'' 2015;21(3):339–350.</ref> It's even possible that copper additions may actually increase the amount of VSCs in the final wine!<ref name="Muller"/> | ||
For those reasons, the best results are obtained by using the minimum amount of copper needed to remove the offensive VSCs.<ref name="Muller"/> To do this, a "bench trial" should be performed to determine the minimum effective amount. Old-fashioned methods such as stirring with a copper pipe should be avoided because that practice may lead to excessively high levels of copper. If a bench trial is too complicated, you may add copper sulfate directly to the wine in incremental amounts (0.05-0.1ppm at a time). However that may end up being more work in the long run. | For those reasons, the best results are obtained by using the minimum amount of copper needed to remove the offensive VSCs.<ref name="Muller"/> To do this, a "bench trial" should be performed to determine the minimum effective amount. Old-fashioned methods such as stirring with a copper pipe should be avoided because that practice may lead to excessively high levels of copper. If a bench trial is too complicated, you may add copper sulfate directly to the wine in incremental amounts (0.05-0.1ppm at a time). However that may end up being more work in the long run. | ||
| Line 116: | Line 116: | ||
* 1% [[copper sulfate]] solution | * 1% [[copper sulfate]] solution | ||
'''Bench trial procedure:'''<ref name="Gardner"/><ref name="Gusmer">[https://www.gusmerenterprises.com/wp-content/uploads/2015/05/Sulfide-Detection-Kit-Instructions1.pdf | '''Bench trial procedure:'''<ref name="Gardner"/><ref name="Gusmer">[https://www.gusmerenterprises.com/wp-content/uploads/2015/05/Sulfide-Detection-Kit-Instructions1.pdf Sulfide detection kit instructions.] Gusmer Enterprises, Inc. Accessed April 2020.</ref><ref name="morewine"/> | ||
# Create a '''0.01%''' copper sulfate solution by adding 1 mL of the '''1%''' copper sulfate solution to a beaker or graduated cylinder and topping it up to 100 mL with water. | # Create a '''0.01%''' copper sulfate solution by adding 1 mL of the '''1%''' copper sulfate solution to a beaker or graduated cylinder and topping it up to 100 mL with water. | ||
# Put 50 mL samples into four glasses. | # Put 50 mL samples into four glasses. | ||
| Line 132: | Line 132: | ||
* Feel free to alter the concentrations evaluated and/or conduct additional trials. As little as 0.05 mg/L may be needed,<ref name="Osborne"/><ref name="Mansfield"/> and the maximum copper should not exceed 6 mg/L.<ref name="Gusmer"/> | * Feel free to alter the concentrations evaluated and/or conduct additional trials. As little as 0.05 mg/L may be needed,<ref name="Osborne"/><ref name="Mansfield"/> and the maximum copper should not exceed 6 mg/L.<ref name="Gusmer"/> | ||
Small amounts of excess copper sulfate (between 0.1-0.2 mg/L) can be removed with bentonite, yeast hulls, or fresh lees additions.<ref name="Gardner">Gardner | Small amounts of excess copper sulfate (between 0.1-0.2 mg/L) can be removed with bentonite, yeast hulls, or fresh lees additions.<ref name="Gardner">Gardner D. [https://extension.psu.edu/sulfur-based-off-flavors-in-wine Sulfur-based off-flavors in wine.] Pennsylvania State University. Published Feb 14, 2020</ref><ref name="Enartis"/> However, the majority of added copper remains in wine and is not readily removed by racking or filtration.<ref name="Jastrzembski"/><ref name="Clark">Clark AC, Grant-Preece P, Cleghorn N, Scollary GR. [https://onlinelibrary.wiley.com/doi/abs/10.1111/ajgw.12114 Copper(II) addition to white wines containing hydrogen sulfide: residual copper concentration and activity.] ''Aust J Grape Wine Res.'' 2015;21(1):30–39.</ref> | ||
'''Other copper products:'''<br /> | '''Other copper products:'''<br /> | ||
[[Copper citrate]] may be a good alternative to copper sulfate because supposedly copper citrate does not totally go into the ionic form, and therefore does not leave as much residual copper in the wine.<ref name="Kaiser"/> | [[Copper citrate]] may be a good alternative to copper sulfate because supposedly copper citrate does not totally go into the ionic form, and therefore does not leave as much residual copper in the wine.<ref name="Kaiser"/> | ||
Kupzit® contains 2% copper citrate. For easy dosage and handling, it is coated onto a mineral carrier material, a particularly pure, high-quality granulated bentonite.<ref>[https://erbsloeh.com/fileadmin/user_upload/pdf/Wine/technical_data_sheet/GB/kupzit-technical_data_sheet-english-erbsloeh.pdf | Kupzit® contains 2% copper citrate. For easy dosage and handling, it is coated onto a mineral carrier material, a particularly pure, high-quality granulated bentonite.<ref>[https://erbsloeh.com/fileadmin/user_upload/pdf/Wine/technical_data_sheet/GB/kupzit-technical_data_sheet-english-erbsloeh.pdf Kupzit®.] Erbslöh Geisenheim GmbH. Accessed May 2020.</ref> | ||
* 1g copper sulfate pentahydrate contains 0.255g copper | * 1g copper sulfate pentahydrate contains 0.255g copper | ||
* 1g copper citrate hemipentahydrate contains 0.353g copper | * 1g copper citrate hemipentahydrate contains 0.353g copper | ||
| Line 143: | Line 143: | ||
Another alternative product is Reduless®, which is a proprietary fining product from Lallemand that can "naturally enhance roundness while treating sulfur problems and reducing phenol related defects".<ref>[https://scottlab.com/reduless-reduless Reduless] | Another alternative product is Reduless®, which is a proprietary fining product from Lallemand that can "naturally enhance roundness while treating sulfur problems and reducing phenol related defects".<ref>[https://scottlab.com/reduless-reduless Reduless.] Scott Laboratories. Accessed April 2020.</ref> However, their claim that it removes DMS is pretty unlikely. Being proprietary, they don't really disclose what's in it, but it includes bentonite, inactivated yeast, and "natural elements which are rich in copper". Reduless® may also be easier to handle compared to copper sulfate solution.<br /> | ||
Suggested usage is 0.10-0.15 g/L, which adds no more than 0.02 mg/L copper (a low amount). If using this product, the copper sulfate bench trial described above isn't helpful since there's not a dosage conversion to determine how much Reduless would be needed to achieve the same effect. | Suggested usage is 0.10-0.15 g/L, which adds no more than 0.02 mg/L copper (a low amount). If using this product, the copper sulfate bench trial described above isn't helpful since there's not a dosage conversion to determine how much Reduless would be needed to achieve the same effect. | ||
| Line 149: | Line 149: | ||
[[Ascorbic acid]] enables the removal of disulfide compounds by converting them to mercaptans, which allows copper to bind with them.<ref name="Mansfield"/><ref name="Off"/><ref name="awri"/> | [[Ascorbic acid]] enables the removal of disulfide compounds by converting them to mercaptans, which allows copper to bind with them.<ref name="Mansfield"/><ref name="Off"/><ref name="awri"/> | ||
First, it's important to make sure that free SO<sub>2</sub> levels are at least 30 mg/L before adding ascorbic acid. Otherwise ascorbic acid will not help, and it will potentially lead to oxidation.<ref name="Mansfield">Mansfield | First, it's important to make sure that free SO<sub>2</sub> levels are at least 30 mg/L before adding ascorbic acid. Otherwise ascorbic acid will not help, and it will potentially lead to oxidation.<ref name="Mansfield">Mansfield AK. [https://cpb-us-e1.wpmucdn.com/blogs.cornell.edu/dist/0/7265/files/2016/11/SulfurOffOdor-1vp1vm4.pdf Kicking up a stink: treatment for sulfur off-odors.] ''Cellar Dweller.'' Cornell University. Published April 2010.</ref><ref name="Gusmer"/><ref name="awri"/> (See [[Sulfite]] and [[SO2 testing]]) | ||
Ascorbic acid in the range of 20-100 mg/L may be used, depending on how strong the off odor is and how well it seemed to respond in the screening evaluation above.<ref name="Gusmer"/> Many sources suggest starting with around 50 mg/L or higher.<ref name="Mansfield"/><ref name="OsborneJ"/><ref name="PI"/> However, the well-respected Australian Wine Research Institute (AWRI) recommends adding much lower levels: For white wines, add 10 mg/L ascorbic acid and then another 10 mg/L the following day. For red wines, add 2 mg/L ascorbic acid and then another 2 mg/L the following day.<ref name="awri"/> However those recommendations are for commercial wine, which may have lower levels of disulfides compared to a problematic home brew. | Ascorbic acid in the range of 20-100 mg/L may be used, depending on how strong the off odor is and how well it seemed to respond in the screening evaluation above.<ref name="Gusmer"/> Many sources suggest starting with around 50 mg/L or higher.<ref name="Mansfield"/><ref name="OsborneJ"/><ref name="PI"/> However, the well-respected Australian Wine Research Institute (AWRI) recommends adding much lower levels: For white wines, add 10 mg/L ascorbic acid and then another 10 mg/L the following day. For red wines, add 2 mg/L ascorbic acid and then another 2 mg/L the following day.<ref name="awri"/> However those recommendations are for commercial wine, which may have lower levels of disulfides compared to a problematic home brew. | ||
| Line 158: | Line 158: | ||
For lower levels or smaller volumes, it may be wise to make a stock solution as described in the screening procedure so that measurements will be more accurate. | For lower levels or smaller volumes, it may be wise to make a stock solution as described in the screening procedure so that measurements will be more accurate. | ||
After the ascorbic acid addition, we need to give the chemical reactions enough time to occur before conducting a copper bench trial (or adding copper to the batch). Unfortunately this process can take days to months, and recommendations for how long to wait are inconsistent.<ref name="Mansfield"/> The AWRI suggests to wait only 24 hours after the second addition of ascorbic acid.<ref name="awri"/> Other sources suggest to wait about 4-5 days,<ref name="Gusmer"/><ref name="OsborneJ"/> or as long as several weeks.<ref name="PI">[https://www.piwine.com/ascorbic-acid-usp-powder-vitamin-c.html | After the ascorbic acid addition, we need to give the chemical reactions enough time to occur before conducting a copper bench trial (or adding copper to the batch). Unfortunately this process can take days to months, and recommendations for how long to wait are inconsistent.<ref name="Mansfield"/> The AWRI suggests to wait only 24 hours after the second addition of ascorbic acid.<ref name="awri"/> Other sources suggest to wait about 4-5 days,<ref name="Gusmer"/><ref name="OsborneJ"/> or as long as several weeks.<ref name="PI">[https://www.piwine.com/ascorbic-acid-usp-powder-vitamin-c.html Ascorbic acid, USP, powder (vitamin C).] Presque Isle Wine Cellars. Accessed March 2020.</ref> If the subsequent copper bench trial is unable to fully remove the odor with reasonable amounts of copper, consider adding more ascorbic acid, or giving it more time. | ||
Ascorbic acid can trigger the release of sulfides and mercaptans from the copper.<ref>Chen, | Ascorbic acid can trigger the release of sulfides and mercaptans from the copper.<ref>Chen Y, Jastrzembski JA, Sacks GL. [https://www.ajevonline.org/content/68/1/91.short Copper-complexed hydrogen sulfide in wine: measurement by gas detection tubes and comparison of release approaches.] ''Am J Enol Vitic.'' 2017;68(1):91–99.</ref><ref name="Jastrzembski"/> Therefore, the lowest effective amount of ascorbic acid may be preferred, so as not to interfere with the action of copper. However, given the slow speed of reaction, and the fact that it doesn't improve the odor by itself, bench trials to determine the lowest effective amount are not practical. The other potential downside of using ascorbic acid is that it can lead to faster oxidation if the level of sulfite is too low. | ||
Note that there are many sulfide compounds that do not respond to fining with ascorbic acid and copper. Examples of these include [[diethyl sulfide]] (DES) and [[dimethyl sulfide]] (DMS). Unfortunately, there is no good or predictable way for us to remove these compounds.<ref name="Gusmer"/> | Note that there are many sulfide compounds that do not respond to fining with ascorbic acid and copper. Examples of these include [[diethyl sulfide]] (DES) and [[dimethyl sulfide]] (DMS). Unfortunately, there is no good or predictable way for us to remove these compounds.<ref name="Gusmer"/> | ||
===Other measures=== | ===Other measures=== | ||
'''Tannins''' - Enartis (a company that produces winemaking products) claims that the addition of tannins, especially ellagic (oak) tannins, has the ability to bind with mercaptans and form odorless complexes. These complexes are supposedly very stable over time and do not entail the risk of a later sulfur off-aroma appearance.<ref name="Enartis"/> However, we can't find any scientific research to support this. In fact, one study showed that adding oak does not seem to affect the levels of VSCs, with or without microxygenation (along with adequate sulfite levels).<ref>McCord | '''Tannins''' - Enartis (a company that produces winemaking products) claims that the addition of tannins, especially ellagic (oak) tannins, has the ability to bind with mercaptans and form odorless complexes. These complexes are supposedly very stable over time and do not entail the risk of a later sulfur off-aroma appearance.<ref name="Enartis"/> However, we can't find any scientific research to support this. In fact, one study showed that adding oak does not seem to affect the levels of VSCs, with or without microxygenation (along with adequate sulfite levels).<ref>McCord J. [https://pdfs.semanticscholar.org/c9d6/21a697015d17a4f4c3ff84203912035194c4.pdf Application of toasted oak and micro-oxygenation to ageing of cabernet sauvignon wines.] StaVin Inc. Published 2003.</ref> There has been some anecdotal success with 0.1-0.2 g/L chestnut tannins for removing H<sub>2</sub>S, but not other VSCs.<ref>[https://www.winemakingtalk.com/threads/sulfide-aroma-sulfur-rotten-egg-prevention-and-removal.71238/#post-751940 Sulfide aroma (sulfur, rotten egg) - prevention and removal.] Wine Making Talk. Published April 2020.</ref> | ||
'''Mineral Oil''' - As crazy as it sounds, disulfides can be removed by adding mineral oil to the wine and agitating it daily for several days. This works because the disulfides are more soluble in oil compared to the wine. When the wine beneath the mineral oil layer smells clean, it should be racked, leaving the oil behind.<ref>Jackisch | '''Mineral Oil''' - As crazy as it sounds, disulfides can be removed by adding mineral oil to the wine and agitating it daily for several days. This works because the disulfides are more soluble in oil compared to the wine. When the wine beneath the mineral oil layer smells clean, it should be racked, leaving the oil behind.<ref>Jackisch P. ''Modern Winemaking.'' Cornell University Press; 1985:95.</ref> An additional racking may be needed to fully remove the oil. This may be useful as a last resort for removing disulfides from wine, but for beer it's probably not a great idea. | ||
'''Silver Chloride''' - This additive is effective for removal of hydrogen sulfide, mercaptans, AND disulfides, but this compound has limited availability, it is relatively expensive, and there is very little information about its use.<ref name="Muller"/><ref name="Kaiser"/> | '''Silver Chloride''' - This additive is effective for removal of hydrogen sulfide, mercaptans, AND disulfides, but this compound has limited availability, it is relatively expensive, and there is very little information about its use.<ref name="Muller"/><ref name="Kaiser"/> | ||
| Line 174: | Line 174: | ||
'''Biology and sulfide formation'''<br /> | '''Biology and sulfide formation'''<br /> | ||
For a review of the biological production pathways, see these articles: | For a review of the biological production pathways, see these articles: | ||
* Wang, | * Wang XD, Bohlscheid JC, Edwards CG. [https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2003.01827.x Fermentative activity and production of volatile compounds by Saccharomyces grown in synthetic grape juice media deficient in assimilable nitrogen and/or pantothenic acid.] ''J Appl Microbiol.'' 2003;94(3):349–359. | ||
* Huang, | * Huang CW, Walker ME, Fedrizzi B, Gardner RC, Jiranek V. [https://academic.oup.com/femsyr/article/17/6/fox058/4056150 Hydrogen sulfide and its roles in Saccharomyces cerevisiae in a winemaking context.] ''FEMS Yeast Res.'' 2017;17(6). | ||
'''Sulfite'''<br /> | '''Sulfite'''<br /> | ||
| Line 181: | Line 181: | ||
'''Myth busting'''<br /> | '''Myth busting'''<br /> | ||
Some sources claim that adding sulfite after fermentation theoretically helps eliminate sulfide by reacting with it.<ref name="Kaiser"/><ref name="awri"/><ref>Heunisch | Some sources claim that adding sulfite after fermentation theoretically helps eliminate sulfide by reacting with it.<ref name="Kaiser"/><ref name="awri"/><ref>Heunisch GW. [https://pubs.acs.org/doi/abs/10.1021/ic50172a033 Stoichiometry of the reaction of sulfites with hydrogen sulfide ion.] ''Inorg Chem.'' 1977;16(6);1411–1413.</ref> However, this appears generally not to be the case in practice, otherwise sulfide would basically never be a problem in wine. Perhaps it is instead related to oxygen exposure. Other sources indicate that H<sub>2</sub>S may simply exist in equilibrium with products of a sulfite + sulfide reaction, which also serve as a latent reserve of H<sub>2</sub>S that would release as sulfite declines during aging — this is arguably even worse than not helping. | ||
Certain sources ([https://beerandbrewing.com/dictionary/6KDwm8vWwW/ Beer & Brewing]) claim that high levels of sulfate in brewing water may lead to increased sulfide production. This isn't supported by any modern science, nor the most modern textbook they reference (''Handbook of Brewing'', 2006).<ref>Priest | Certain sources ([https://beerandbrewing.com/dictionary/6KDwm8vWwW/ Beer & Brewing]) claim that high levels of sulfate in brewing water may lead to increased sulfide production. This isn't supported by any modern science, nor the most modern textbook they reference (''Handbook of Brewing'', 2006).<ref>Priest FG, Stewart GG. ''Handbook of Brewing.'' 2nd ed. Taylor & Francis Group, LLC.; 2006:308.</ref> Jiranek (1992) showed that fermentations containing as much as 4800ppm sulfate (50mM) produce negligible amounts of sulfide.<ref name=thesis/> | ||
'''Chemistry'''<ref name="Kaiser"/><ref name="Zoecklein2"/><br /> | '''Chemistry'''<ref name="Kaiser"/><ref name="Zoecklein2"/><br /> | ||
| Line 202: | Line 202: | ||
'''Cysteine'''<br /> | '''Cysteine'''<br /> | ||
The amino acid cysteine is commonly referenced as contributing to increased formation of hydrogen sulfide, but in practice its effect is negligible since cysteine concentration in must is typically very low.<ref name=thesis>Jiranek | The amino acid cysteine is commonly referenced as contributing to increased formation of hydrogen sulfide, but in practice its effect is negligible since cysteine concentration in must is typically very low.<ref name=thesis>Jiranek V. [https://digital.library.adelaide.edu.au/dspace/bitstream/2440/21637/2/02whole.pdf Hydrogen sulfide formation in ''Saccharomyces cerevisiae'' and its regulation by assimilable nitrogen.] Doctoral thesis for University of Adelaide. Published August 1992.</ref><ref name="Osborne"/><ref name="Giudici"/><ref name="Moreira"/><ref name="Huang"/><ref name="Jiranek"/><ref name="Huang"/><ref name="Jiranek2002"/> It's believed that aspartate aminotransferase deaminates cysteine to give mercaptopyruvate, which in a subsequent step catalyzed by MST liberates H<sub>2</sub>S and pyruvate.<ref>Kabil O, Banerjee R. [https://www.jbc.org/content/285/29/21903.full.pdf Redox biochemistry of hydrogen sulfide.] ''J Biol Chem.'' 2010;285(29):21903–21907.</ref> However, that hasn't been fully confirmed by other sources.<ref name="Huang"/> | ||
'''Methionine'''<br /> | '''Methionine'''<br /> | ||
Methionine addition has a variable effect on hydrogen sulfide (and sulfite) production, and the effect also varies by yeast strain.<ref>Boudreau, | Methionine addition has a variable effect on hydrogen sulfide (and sulfite) production, and the effect also varies by yeast strain.<ref>Boudreau TF IV, Peck GM, Ma S, et al. [https://onlinelibrary.wiley.com/doi/full/10.1002/jib.449 Hydrogen sulphide production during cider fermentation is moderated by pre-fermentation methionine addition.] ''J Inst Brew.'' 2017;123(4);553–561.</ref><ref name="Giudici"/><ref name="Moreira"/><ref name="Duan"/><ref name="Spiropoulos"/> | ||
==See | ==See also== | ||
* [http://allaboutbeer.com/article/sulfur-in-beer/ Article about VSCs in beer] by Randy Mosher. | * [http://allaboutbeer.com/article/sulfur-in-beer/ Article about VSCs in beer] by Randy Mosher. | ||
* [https://wineserver.ucdavis.edu/industry-info/enology/fermentation-management-guides/wine-fermentation/characters Scientific discussion of the variety of VSCs and their formation] from UC Davis. | * [https://wineserver.ucdavis.edu/industry-info/enology/fermentation-management-guides/wine-fermentation/characters Scientific discussion of the variety of VSCs and their formation] from UC Davis. | ||