Brett beer fermentation

[spiderwrangler]

If the airlock is kept filled, there should be minimal oxygen ingress to the headspace.

[BrewerJ]

Minimal but much greater than a keg or bottle.

[Ozwald]

I have noticed that when brett is exposed to large amounts of oxygen such as bulk aging in a carboy not filled to the top it seems to increase acetic acid production. That is one reason I don't recomend aging brett beers in carboys for long periods.

Good observation. The acetic acid production by those strains of Brett is an aerobic process. Flavor-wise, it works in small amounts, but trying to increase it to sour a beer is not a great idea. It's not that same sour character you get from lacto or pedio. It tends to be more harsh, vinegar-y & 1 sided. I've never had one get that far - I'd imagine you'd need to actively add more O2, but I suppose it could get there with a long aging time. Either way, something to be avoided.

[BrewerJ]

I haven't let one go that far either. I have let one go far enough as to give an acetic character to a beer. I am sensitive to acetic acid and don't really care for it. I however, love lactic acid and sour beer as long as it isn't to acetic.

[crashlann]

But a certain amount of oxygen is desired right? Isnt that one of the reasons Russian River and the sorts use barrels, and the theory behind the wood dowel in the ferementor etc,...? Would it be a good idea to purge the headspace in a carboy with CO2 before extended aging. There will still be some O2 movement into the vessel, but much less than the 21% room air would leave in that head space.

[BrewerJ]

I have two barrels that I age sour beers in, they do benefit from micro oxygenation but it is a whole cocktail of bugs and bretts. If I am fermenting straight brett beer i like to treat it like i would an ipa or kolsch and really minimize 02 exposure. That will help and keep an airlock on with the carboy near full. Or just use a keg which is what I like to do.

[piratwolf]

I have two barrels that I age sour beers in, they do benefit from micro oxygenation but it is a whole cocktail of bugs and bretts. If I am fermenting straight brett beer i like to treat it like i would an ipa or kolsch and really minimize 02 exposure. That will help and keep an airlock on with the carboy near full. Or just use a keg which is what I like to do.

Does this only apply to extended aging, or is it even true during the primary fermentation? I'm trying my first all-Brett (Brux) Pale Ale. I thought I'd heard a BN interview where it's okay to add O2 for primary--but can't recall where/when it was.

[BrewerJ]

Primary is fine no need to worry and oxygen is good at the start of fermentation. In my experience its when fermentation is complete and you just leave it in the carboy the Brett will start to produce acetic characters since there isn't any sugar for it to consume.