Bottling Tip - Rack your Headspace

[doc_rob]

Short version:

Slowly pump some CO2 out of your fermenter into your bottling bucket with your autosiphon before racking the beer.

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Long Version:

I bottle and have had some oxidation issues since I started brewing - a cardboard flavor would start to creep into the beer starting at about 3 weeks on. I had been trying to come up with a way to blanket the bottling bucket with CO2 and reduce the beer's exposure to O2, but didn't want to invest in any special equipment. The people who keg always talk about flushing all vessels that will hold the beer with CO2 before moving the beer, but I don't have that equipment.

I kept thinking - where can I get a decent amount of CO2 to put in the bottling bucket before I rack? Open a can of soda?

Then it hit me: the headspace of my fermenter is full of CO2.

If this sounds stupid and it looks like I'm just overthinking things, feel free to ignore this tip, but the great thing is, it takes zero extra work or equipment. Just pump your autosiphon once and wait a few seconds (I repeated this occasionally for about a minute) . I did this on my last batch and have had zero cardboard flavor 8 weeks on.

If anyone wanted to test the efficacy of this technique, you could put a lit candle in the bottom of your bottling bucket before pumping in the CO2, and see if the gas puts the candle out.

The next time out I might even try and spray a bit of C02 around the upturned empty bottles before I fill. Might as well - it's free CO2 that's going to waste otherwise.

Anyway, I hope this is of interest to some of you out there. Figuring this out made me feel like a genius and a ******* all at the same time, so I thought it was worth sharing.

 

[TJTHEBEST]

Wouldnt pumping the CO2 out of the fermenter cause oxygen to enter the fermenter?

 

[doc_rob]

There's no way you're going to clear out all the CO2 in the fermenter, so there will still be a blanket there for the next 10 minutes until it's been racked into the bottling bucket (where it will spend an hour or so waiting to be bottled).

 

[zachattack]

There's no way you're going to clear out all the CO2 in the fermenter, so there will still be a blanket there for the next 10 minutes until it's been racked into the bottling bucket (where it will spend an hour or so waiting to be bottled).

I don't think that your lack of oxidation with this batch is due to your new technique.

The whole "CO2 blanket" concept is a little flawed. CO2 is heavier than air, but it will still mix readily with air so any "blanket" protection is very short lived. As soon as you open the fermenter, air will start to mix with the CO2. If you're using a bucket it's going to happen a lot faster than if you're using a carboy. Pumping out some of the CO2 will cause the air to be drawn in a little faster, but really there's no way to "fill a bucket" with CO2. Let's say you have 1 gallon of headspace in your fermenter, and a 6 gallon bottling bucket. You somehow manage to transfer all that CO2 to the bucket, but it's going to immediately start mixing with air. Even if you purged the bucket completely full of CO2 from a tank, it would all be gone after a minute or two. And if you pulled all the CO2 out of your fermenter, then now the beer's being exposed to air in the fermenter.

Your process isn't going to hurt anything, but it's entirely unnecessary. Because the beer is saturated with CO2 and you're agitating it slightly during transfer, it will release some of that CO2 as you siphon it, essentially doing the same thing that you're describing. In either case, the "blanket" of CO2 isn't going to stick around in an open bottling bucket with a big opening. Purging with CO2 can help in a carboy or keg (with narrow openings) but I don't think it'll do much in a bucket.

Your best bet for minimizing oxidation during bottling is to siphon gently, avoid splashing, and hurry the hell up. If it takes you 10 minutes to siphon and your beer sits in the bottling bucket waiting to be bottled for an hour, that's your problem. Siphoning only takes a couple minutes (buy a 1/2" autosiphon if your 3/8" one is too slow) and even if I'm alone, it only takes maybe 10-15 minutes to bottle 50-60 beers. Most of my time on bottling day is spent sanitizing bottles, making the priming solution, siphoning, and cleaning the carboy after.

I'd just focus on speeding up your process, and you can buy O2 absorbing caps if you're still concerned. I obviously think it's pointless, but if you really want to flood your bucket with CO2 I would mix baking soda with an acid (vinegar might be too stinky) in a big plastic jug, and have a tube directing the CO2 into your bucket.

 

[BetterSense]

The bottle-fermenting yeast are supposed to consume oxygen dissolved in the beer, correct? I have never had an oxidation problem with regular caps and I have drank some beers that were well over a year old. I have also been known to leave the beer in the bottling bucket for a while to let it settle a bit before bottling. Do you use a secondary? Maybe that's where your oxidation is happening.

 

[doc_rob]

Zach, thanks for the advice, good stuff. I had no evidence that it's doing anything, but I thought, it can't hurt and it's effortless, so, why not? My only reason for thinking the C02 would remain settled in the bottom of the bucket and at least reduce the beer's exposure to O2 was the ol' put-out-the-candle-with-CO2 trick:

But, I got a D in chemistry lab, so what do I know? My thinking was: Even if it is mixing, it's probably still diluting the presence of oxygen. Again - no evidence, just worth doing, in my opinion.

BetterSense - No secondary, I use Oxy caps and bottle condition, which is why I started looking at the bottling bucket.

 

[zachattack]

You're right in that CO2 is can displace air and fill a vessel. And do neat things like extinguish candles in an aquarium

I'm just saying that it's not going to stay in that vessel for a very long time when it's open to the air on top. So the concept of a co2 "blanket" that creates an impenetrable layer is rather exaggerated. CO2 can certainly protect your beer, and it's true that I don't have any exact evidence of how long that "blanket" lasts. But in an open bucket I'm sure the time scale is much closer to minutes than hours.

Gases like to mix with each other fairly rapidly compared to liquids, due to the kinetic/molecular theory of gases. If you fart in the corner of the room, you'll smell it on the other side of the room a minute later. Similarly, if your bucket is full of CO2, it will soon diffuse into the air and be well dispersed.

I have an idea for an experiment: fart into your bottling bucket, then fill the bucket with water, then bring it into another room and see if you can still smell the fart above the water in the bucket.

 

[doc_rob]

I have an idea for an experiment: fart into your bottling bucket, then fill the bucket with water, then bring it into another room and see if you can still smell the fart above the water in the bucket.

Your experiment is interesting, it could bring new meaning to the term "brownian motion."

Heyoo!

I cannot argue with your science, but I do have something on my buckets that might be prevent the inevitable dispersion of the gas: Lids.

 

[zachattack]

hahaha. A lid would certainly slow it down!

 

[Revvy]

There's co2 coming over with your beer already, it's in the solution, you kick it up when you're racing, normally. One of the reasons we fill our beer from the bottom of the bottle upward is that we're pushing the o2 out of the headspace. That's why we also fill all the way to the top of the bottle. This also pushes out a lot of the o2 in the bottle.

Finally the reason we don't crimp the caps right away, leaving them on for a bit while we fill more bottles, is that the tiny bit of fermentation that is ALREADY starting from all the activity of racking, and adding fresh sugar, along with the residual co2 also helping to push o2 out of the headspace, that's why sometimes you can even have the caps pop off the top while they're sitting there.

There really isin't a need for all that kerfuffle, what little oxygen the is left in there will actually be consumed during the "minifermentation" that is bottle carbing, yeast like oxygen during fermentation, remember. And of course co2 will be generated filling the headspace.

Bazillions of bottles of beer have been conditioned for decades without needing to do anything "special," to them, and they don't oxidize. With careful bottling, the whole process is pretty well setup to protect the beer.

 

[Varmintman]

It has been my experience that oxidation in the short term is vastly overrated. I also through stupidity on my part have oxidized rather thoroughly a batch of beer right before bottling and found 2 months later no taste of wet cardboard. I just wonder how bad it can be at three weeks when I poured a entire gallon keg through a little hole back into my bottling bucket and was fine 2 months later

Not saying that oxidation does not exist but that I think it is a long term storage problem. I also think that during bottling if through handling or early start of fermentation Co2 is released and replaces all the air in the headspace of the bottle if you just set the caps on for a bit.