Sampling the Lambic

I have a lambic of sorts brewed 1/1/10 pitched with a variety of bacteria across the lambic spectrum: Brett B and a few sour blend packs.

My question is about sampling. I want to taste it to see how it's coming, so I can determine when to keg it, but I'm concerned about introducing too much O2. I understand that some bacteria are aerobic and some are anaerobic, but I don't have a sense for how much O2 I'm letting in (if any) when I go into the carboy to grab a small (<1 oz) sample.

Is there a rule of thumb? Can I sample as often as I like? Or should I just check on it every three months?

Thanks

I'd check it once a month.

Also... did you pitch just brett lambic mix? Or did you use a starter yeast to do the bulk of the work? I like using US-05 initially and then after that's done it's thing, I pitch my lambic mix and let it go to town for 9+ months.

Sample as often as you like. But every time you sample, that's less beer you end up with.

Beernik said:

Sample as often as you like. But every time you sample, that's less beer you end up with.

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Yeah, but you didn't waste it, you're still drinking it...

I'd say sample once a month. Why not? It's your beer.

One of the blends had a normal yeast in it, but I pitched it all at the start.

My main question was about O2 as it relates to aerobic and anaerobic activity, but I guess I'm overthinking it.

it should have a pellicle which is a barrier against O2, try to disturb this as little as possible, but it should reform in the area where you took your sample.

Last I checked there was no pellicile, but it does taste sour and lambic-like. I'll have to check it out.

As long as some fermentation is taking place, carbon dioxide is being produced. CO2 is heavier than O2 and will blanket your beer.

I find it easier to forget about my sours as much as possible. I try not to pull samples more often than every 2-3 months. Try to get a few going so you always have something getting close to the end of the pipline.

I don&#8217;t worry too much about oxygen getting in if there isn&#8217;t much headspace, but a pellicle and fermentation will not protect your beer completely. After the initial burst of fermentation very little CO2 is being produced (the lactic acid bacteria don&#8217;t make much). Pellicles form in response to oxygen, so if you don&#8217;t have one it just means not much air is getting in (a good thing). Make sure your airlock stays topped off.

Beernik said:

As long as some fermentation is taking place, carbon dioxide is being produced. CO2 is heavier than O2 and will blanket your beer.

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Yes, this is why we can't breathe at sea level. Fluid dynamics is a lot more complicated than "this is heavier than that, so it sinks."

maskednegator said:

Yes, this is why we can't breathe at sea level. Fluid dynamics is a lot more complicated than "this is heavier than that, so it sinks."

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I don't know about you, but I've had no issues breathing at sea level. And while you maybe right about fluid dynamics (I'm no scientist), the poster you're replying to is right. Some CO2 does become absorbed into the beer, but there's enough of it floating above the beer to "blanket" it from oxygen. When you start talking about oxygen and co2, we're no longer talking about fluid dynamics...

Suthrncomfrt1884 said:

I don't know about you, but I've had no issues breathing at sea level. And while you maybe right about fluid dynamics (I'm no scientist), the poster you're replying to is right. Some CO2 does become absorbed into the beer, but there's enough of it floating above the beer to "blanket" it from oxygen. When you start talking about oxygen and co2, we're no longer talking about fluid dynamics...

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You are _definitely_ still talking about fluid dynamics, and no, the CO2 blanket doesn't keep O2 at bay though it will decrease the amount in contact to some degree.

He mentioned breathing because air itself is part CO2. If the heavier CO2 just sank to the bottom and the O2 floated on top of it, you wouldn't be able to breath at sea level.

Thank you, Sumner.

A fermentor with an airlock is a semi-closed batch reactor. The air in a fermentor is not terribly turbulent. Certainly not turbulent enough to compare it to the atmosphere. Since O2 and N2 are lighter, they are pushed out the airlock first, and will be the majority of what is pushed out until at least 50% of the air in the air layer is CO2.

I'd love to see the jet stream and 20 mph winds that routinely scour through your carboy.

Your analogy is only accurate if using open fermentation. Even then only marginally accurate unless the surface of the fermentation is exposed to scouring winds. Anyone who has that open of a fermentation deserves wet cardboard flavors.

Beernik said:

A fermentor with an airlock is a semi-closed batch reactor. The air in a fermentor is not terribly turbulent. Certainly not turbulent enough to compare it to the atmosphere. Since O2 and N2 are lighter, they are pushed out the airlock first, and will be the majority of what is pushed out until at least 50% of the air in the air layer is CO2.

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This isn't right. Google "partial pressure" for a starting point if you're interested.

Air turbulence or wind is irrelevant--gases simply don't stratify like that. You'd actually get identical amounts of O2 and N2 pushed out if you had the airlock attached just above the surface of the beer (down where you should just be pushing out CO2 if things were sitting in neat little layers as you imagine) as you do with it up at the top of the fermenter.

It's also getting pretty far off topic, though. Oldsock's comment was the best of the thread:

I find it easier to forget about my sours as much as possible. I try not to pull samples more often than every 2-3 months. Try to get a few going so you always have something getting close to the end of the pipline.

I don&#8217;t worry too much about oxygen getting in if there isn&#8217;t much headspace, but a pellicle and fermentation will not protect your beer completely. After the initial burst of fermentation very little CO2 is being produced (the lactic acid bacteria don&#8217;t make much). Pellicles form in response to oxygen, so if you don&#8217;t have one it just means not much air is getting in (a good thing). Make sure your airlock stays topped off.

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Again, you are talking about a completely closed system where air cannot escape. A volume of CO2 produced at the surface displaces a volume of air out of the airlock.

The no-slip condition, because there is no wave action across the top of the fermentation, would suggest there is always a layer of CO2 blanketing the wort. A mol of CO2 produced at the surface is not instantly mixed into air above it.

Beernik said:

Again, you are talking about a completely closed system where air cannot escape. A volume of CO2 produced at the surface displaces a volume of air out of the airlock.

The no-slip condition, because there is no wave action across the top of the fermentation, would suggest there is always a layer of CO2 blanketing the wort. A mol of CO2 produced at the surface is not instantly mixed into air above it.

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What happens when you open the airlock and pull a sample with a thief? You're not thinking this through.

Beernik said:

Again, you are talking about a completely closed system where air cannot escape. A volume of CO2 produced at the surface displaces a volume of air out of the airlock.

The no-slip condition, because there is no wave action across the top of the fermentation, would suggest there is always a layer of CO2 blanketing the wort. A mol of CO2 produced at the surface is not instantly mixed into air above it.

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The density differences in gases is very small, and gases by nature are very high energy states of matter, given time in a vessel gases will tend toward more homogeneity than stratification

Think about the basic thermodynamic principle of increasing disorder of a syste

ryane said:

The density differences in gases is very small, and gases by nature are very high energy states of matter, given time in a vessel gases will tend toward more homogeneity than stratification

Think about the basic thermodynamic principle of increasing disorder of a syste

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Exactly. All the handwaving and wishing in the world isn't going to changes the actual physics of the situation.

That aside, I think the argument's pretty much done, now; Oldsock's got the actual, brewed-a-zillion-sours hands-on answer to the question.

OP here. I just sampled it again. It's kind of one-dimensional almost lemony sour. There's a hint of the bretty horsiness kind of thing, but mainly just sour. Is this a normal 9 month old lambic/sour? Should I be doing anything to it?

At this point I'm waiting for a sample to blow me away, then I'm planning to keg it up and cool it down to try to stop it at "the perfect moment".

ksbrain said:

OP here. I just sampled it again. It's kind of one-dimensional almost lemony sour. There's a hint of the bretty horsiness kind of thing, but mainly just sour. Is this a normal 9 month old lambic/sour? Should I be doing anything to it?

At this point I'm waiting for a sample to blow me away, then I'm planning to keg it up and cool it down to try to stop it at "the perfect moment".

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It’s normal for this batch of sour beer. Give your beer a bit more time and hopefully the ester/funk profile will get to where you want it. You could certainly add some more bottle dregs if you want to up the microbial diversity, but if you are getting some funk the Brett is already hard at work.

Lambic brewers splitting the same wort from the same coolship into barrels in the same room can get wildly different results barrel to barrel. Their “perfect” sour is usually the result of blending some of these suboptimal batches to bring out the best of each. Your batch may never get to that perfect point alone, but it certainly could.

One of my favorite things about brewing sours is to watch the evolution over time, which is why I almost always bottle them even though I finally started kegging a year ago.