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How to Solve "Rotten Egg" Smell in Wine

Where does the smell come from? | The causes of hydrogen sulfide contamination
Prevention of H2S | Treatment | Conclusion | References

Ever smelled rotten eggs when you racked your wine? We sure hope not, but if you have, your wine has been bitten by the dreaded hydrogen sulfide bug. No one wants to drink wine that smells like rotten eggs, so is there anything you can do to save the wine? You bet. Better yet, we'll offer some tips that should help you avoid the problem in the first place.

Hydrogen sulfide (H2S) usually forms at the end of fermentation, but most home winemakers won't notice a smelly problem until the first racking. If you do smell rotten eggs, the quicker you can act, you'll increase the chances of saving your wine. If you tarry too long before treating the wine, hydrogen sulfide will react with other carbon compounds in the wine to create mercaptans, and later into disulfides. These boogers are extremely difficult to remove from your wine once formed, so the faster you can detect and treat your wine for hydrogen sulfide, the better!

The possible causes of hydrogen sulfide contamination are myriad:

  • Too much sulfites, usually the result of grapes being dusted with too much sulfur during the growing season.
  • Lack of proper nutrients (nitrogen, yeast hulls) during fermentation.
  • Yeast combining with various forms of sulfur (some folks swear that Red Star Montrachet yeast is notorious for causing H2S, but we've never experienced this ourselves).
  • Bacterial contamination due to poor sanitation technique.

That being said, here are the things you can do to prevent H2S contamination:

  • Add proper amounts of sulfites to wine.
  • If making wine from scratch (not from a kit), add a proper amount of yeast nutrient prior to pitching yeast (Fermax, DAP, etc.).
  • Use proper yeast for the wine you're making, and make sure it has not passed the expiration date or gotten too hot in storage.
  • Maintain sanitary conditions for your equipment and must (especially prior to pitching yeast).

If the cat's out of the bag and you've already got a rotten egg smell, you could do what the big wineries do and add the correct (teensy-weensy) amount of copper sulfate to your wine... but we don't recommend you do that, unless it's a last resort.

The reason? Copper sulfate is poisonous! grapestompers recommends a gentler, phased approach to solving this problem - if H2S is caught quickly enough, you may be able to solve the problem with chemicals you already have on hand.

Here's what we recommend you do:

  • First, measure the amount of sulfites in your wine using a test kit
  • If deficient, treat wine to 50 PPM sulfites
  • Rack and splash - rack your wine two or three times, being sure to splash it around a lot as the wine goes from vessel to vessel. The aeration (introduction of oxygen) will help counteract the H2S.
  • Put the airlock back on and wait a couple of hours or overnight. If it still smells like rotten eggs, keep going...
  • Get a piece of copper (i.e. copper flashing) from a home supply store.
  • Pour the wine over the copper so that it runs over the surface of the metal into a receiving vessel.
  • Fine or filter the wine.
  • By now, the sulfur smell should at least be greatly diminished. If you can still detect a smell (we've heard that humans can detect H2S in quantities as low as 2 parts per billion), you might try to use an egg white or a gelatin fining agent and fine your wine. Add normal amounts recommended by the manufacturer.
  • Filter wine through a tight filter.
  • When all else fails you can use copper sulfate on your wine. A 0.1% solution added at about 0.5 ml per gallon, will give you about 0.3 PPM copper sulfate in your wine. BE CAREFUL. Remember, this stuff is poisonous. DO NOT EXCEED 0.5 PPM of copper.
  • Fine your wine with a bentonite or Sparkolloid fining agent. This will remove all the copper sulfate.
  • Filter wine if necessary to remove fining agent.

A rotten egg smell doesn't necessarily mean you throw away your batch of wine... it simply means your wine has a hydrogen sulfide problem. It's easily treated if caught in the early stages, but you can bring in the heavy stuff if need be. Of course, it's much better to prevent H2S from forming in the first place, by ensuring proper winemaking techniques and sanitation.

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