4

When fermenting wine in a steel tank, should one put on the lid or should one leave it open?

Now as I understand, if it's open to oxygen, the yeast will multiply much faster and so the fermentation could kick on really fast.

But can the yeasts still multiply if the lid is on (with a pumped up silicon tube but I left 20 cm or so air between the must and the lid)?

3

Your biggest worry with an open fermentor is contamination. If you've added potassium or sodium metabisulfide to the wine must, you should be safe against most wine spoiling bacteria. However, it is advisable to cover the fermentation vessel. See this post about open fermentation.

  • Yeah, but what about a closed tank when there's not too much oxygen? Can it be a problem? – Balázs Németh Oct 11 '16 at 9:10
  • In times like these, I defer to Charlie Papazian for the best advice. – Rube Oct 13 '16 at 4:07
  • Relax, Don't worry, Have a Homebrew. You can aerate your wine must before fermentation to help oxygenate it but unless you are fermenting over years, the amount of oxygen needed to convert sugar to alcohol is not than much. Or use Olive Oil. – Rube Oct 13 '16 at 4:14
  • I have around 650 liters of must, so it's not such a small amount to risk :) But one tank has already started up, I'll definitely have something to drink next year! Thanks – Balázs Németh Oct 13 '16 at 7:36
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I was a professional wine maker for a few years. We always used open top fermenters on our red wines when they were fermenting on the skins, we just threw sheets or blankets over them to keep the bugs out. Of course we are talking about tons of grapes at a time. White wines you could do this too, but I would only as long as there is active fermentation and enough CO2 to keep the oxygen out. But for white wines we had a closed lid with way for the CO2 to escape easily. Sulfites will be blown out with an active fermentation so they are pretty useless while fermenting, but they need to be added as soon as fermentation is done. As long as there is active fermentation, it is very hard to oxidize your wine as most of the oxygen will be consumed by the yeast.

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I always cover with a tea towel and tie it round the rim with string, still allows it to breathe and fights off nearly all air borne infections. You are right about the fact fermentation will be faster with the lid open, be wary of the fact it can happen to fast - if its bubbling a lot then you would be better to decrease the heat that the pan is sitting on, be that a heat mat or a floor. Happy brewing!

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