What causes hydrogen sulfide (HS2) contamination (rotten egg smell)?

There are many things that can cause hydrogen sulfide contamination, all are preventable:

  • Too much sulfite, 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.
  • Bacterial contamination due to poor sanitation techniques.
  • 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.
  • 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).