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I see comments on YouTube about how oxygen is bad for mead. However, according to Wikipedia, oxygen is good for yeast to develop resistance to alcohol.

https://en.wikipedia.org/wiki/Yeast_in_winemaking#The_role_of_oxygen

Yeasts are facultative anaerobes meaning that they can exist in both the presence and absence of oxygen. While fermentation is traditionally thought of as an anaerobic process done in the absence of oxygen, early exposure of the yeast to oxygen can be a vital component in the successful completion of that fermentation. This is because oxygen is important in the synthesis of cell "survival factors".

What is wrong with aerating a fermenter or introducing oxygen during racking? Won't that strengthen the yeast for secondary fermentation?

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You are confusing a couple of things. You want oxygen for a robust fermentation, no doubt about that. BUT, after the primary fermentation is done, you want to cut off the supply of oxygen otherwise the mead/wine/beer will oxidize because there is nothing to consume the oxygen. With beer we replace that with CO2, but with mead and wine you need to do something to keep the oxygen away. That means in an aging vessel with little headroom and probably potassium metabisulfite which is a strong antioxidant. Mead doesn't undergo a secondary fermentation, unlike wine. But even then, the bacteria that causes that does not need oxygen to work.

Long story short, during primary lots of oxygen. After primary is over, keep oxygen away.

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  • mostly formation of vinegar in mead when exposed to oxygen?
    – chthon
    Jun 13, 2019 at 15:22
  • @chlthon Only an issue you have an acetic acid producer contaminating the mead. Not a problem for normal mead yeasts.
    – brewchez
    Jun 13, 2019 at 15:30
  • Ok but why is oxidizing bad? You said "the mead/wine/beer will oxidize because there is nothing to consume the oxygen" but still didn't say why that is a bad thing. What does it mean "to oxidize"? Isn't oxygen good for you? They even have oxygen bars. Sick people get put on oxygen.
    – Chloe
    Jun 15, 2019 at 16:19
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    @Chloe First mead is a different animal than Wine. Wine grapes have a fair amount of tannins and other antioxidants that buffer the effects of oxygen and help make wine soften it's hard edges over time. Mead is honey and water. Mead does age but more like a white wine. Oxygen turns the flavors of mead into a stale awful tasting mess if you expose it to too much oxygen. Tiny amounts are good for aging, large amounts are bad.
    – farmersteve
    Jun 16, 2019 at 15:53

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