Brett beer fermentation

[CRBrewHound]

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.

Putting wood in a ferementor is for flavor not for oxygen, as for barreling, oxygen is an unfortunate side effect of it. They are putting it in barrels to infuse the beer with the flavors of the wood and the previous occupant of the barrel. This is not to say that a small amount of oxidization can not be a flavor component of a really good beer. But, it is not a goal of the brewer, I think if most brewers had the opportunity to remove the oxygen exchange they wood, as it hinders the ability to age the beer for long periods of time as the oxidization flavor becomes more pronounced as time continues.

However, you don't really need to fush carboys with CO2 as the fermentation drives the CO2 out of the carboy as fermentation happens. Also, oxygen is important for yeast cell multiplication during the intial steps of ferementation. However, the oxygen in the head space does not add much as it is the dissolved oxygen that is needed. So you could, if it helps you sleep better at night, but really should not be necessary.

[spiderwrangler]

Micro-ox can play a role in the formation of some of the acids involved in certain beers.

[BrewerJ]

i dont know the science behind it but i do know that the beers in my barrels sour much faster than beers in a carboy with the same cultures.

[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.

Putting wood in a ferementor is for flavor not for oxygen, as for barreling, oxygen is an unfortunate side effect of it. They are putting it in barrels to infuse the beer with the flavors of the wood and the previous occupant of the barrel. This is not to say that a small amount of oxidization can not be a flavor component of a really good beer. But, it is not a goal of the brewer, I think if most brewers had the opportunity to remove the oxygen exchange they wood, as it hinders the ability to age the beer for long periods of time as the oxidization flavor becomes more pronounced as time continues.

However, you don't really need to fush carboys with CO2 as the fermentation drives the CO2 out of the carboy as fermentation happens. Also, oxygen is important for yeast cell multiplication during the intial steps of ferementation. However, the oxygen in the head space does not add much as it is the dissolved oxygen that is needed. So you could, if it helps you sleep better at night, but really should not be necessary.

My mistake, I thought it was a combination of both wood character and allowing some oxygen into the vessel, mirroring a barrel. I thought I heard Jamil talk about it on a podcast, but that doesnt mean anything. Was it the one with Vinny talking about brewing with bugs?? Cant remember...

[spiderwrangler]

Putting wood in a ferementor is for flavor not for oxygen, as for barreling, oxygen is an unfortunate side effect of it. They are putting it in barrels to infuse the beer with the flavors of the wood and the previous occupant of the barrel. This is not to say that a small amount of oxidization can not be a flavor component of a really good beer. But, it is not a goal of the brewer, I think if most brewers had the opportunity to remove the oxygen exchange they wood, as it hinders the ability to age the beer for long periods of time as the oxidization flavor becomes more pronounced as time continues.

The movement of beer into the wood, as well as a slight level of oxygen coming in is important for some barreled styles, especially the sours. If they truly didn't want any oxygen entering the barrel, the outside could easily be sealed over with something non permeable. That being said, the tiny amounts coming in through the wood are next to nothing compared to oxygen coming in through air in the headspace.

http://byo.com/stories/issue/item/68-a-barrel-of-fun

[Ozwald]

Micro-ox can play a role in the formation of some of the acids involved in certain beers.

Which can be desirable traits in some styles, not an unfortunate side effect. Flander's Red for example, would not be the same style without a touch of that acetic quality requiring oxygen.

i dont know the science behind it but i do know that the beers in my barrels sour much faster than beers in a carboy with the same cultures.

Simple really. Some bacteria work in no oxygen environments, some work in oxygen rich environments. Of the big 3 we talk about most of the time, Lacto & Pedio like no oxygen & produce the acids that create gentle sour flavors. The third is Acetobactor which prefers oxygen & produces an acid that creates a harsh sourness.

It takes a lot longer for the gentle flavors to build up to create the perception of 'very sour', than it does for the harsh flavors.

[BrewerJ]

I wasn't clear enough before. I understand the basics but in my experience barrels will make the exact same wort sour in half the time. With zero acetic acid, so it's not that. Some species of lacto work in the presence of oxygen. Some produce alcohol and lactic acid some just lactic. There are lots of other acid producing bacteria but they aren't usually desired in their flavor profiles.

I can't explain the magic behind a barrel, but if you make lots of sour they are a great addition to the brewery.

[Ozwald]

That was my whole point. There is acetic acid being created simply because it's in the barrel. The organisms producing the acetic acid only do so in the presence of oxygen, which the barrel is letting in. If you were to split identical wort between a closed stainless vessel & a barrel, the barrel will always sour faster from the acetic acid production that's going to be stifled in the stainless system that is preventing the oxygen from contacting the beer. And it's not necessarily souring more quickly as much as the acids being produced are more harsh, which creates an up-front, aggressive perception of sourness - the difference between how sour something tastes versus it's actual measured pH. All barrel fermented/refermented beers will have some level of acetic acid present, however with many beers it's not as evident since another culture already has taken over the beer limiting how much acetic acid is able to be formed. I believe the pitch-lined barrels also slow down the rate & amount of oxygen that's being let in, but I could be wrong on that particular point.

Also many strains of Lactobacillus are aerotolerant. They don't like being in an environment with oxygen but with enough manganese in solution, they are able to survive. As far as I know, no strain of Lacto prefers an oxygen environment & even those that will still work in it would be doing much better in the anaerobic environment - even without the additional competition that the aerobic environment presents.