Oops! Forgot To Purge Keg Before Beer Went In!

[Greg Lawrence]

I usually fill 2 bottles per brew and keg the rest of it.
Maybe I should be purging the bottles of oxygen before filling to get a better result.
Do any of you purgers do this?

 

[Aus_Rider_22]

I usually fill 2 bottles per brew and keg the rest of it.
Maybe I should be purging the bottles of oxygen before filling to get a better result.
Do any of you purgers do this?

ha! That's actually an interesting point I hadn't thought of! :huh:

 

[Thirsty Boy]

Surely purging the keg with co2 once filled (before force carbing) would overcome this problem.
I dont think the beer would absorb too much oxygen when filling the keg as it is not under any pressure.

Gregor

Better than not doing it - but not as good as purging

if you are going to "naturally" carbonate in a keg should you purge the Keg with CO2?

I had one keg, I filled with CO2 then burped and naturally carbonated and when I put it in the freezer (3 weeks later) it was seemed as though it had not carbonated.

The one I did a couple of weeks ago I didn't purge or burp and when I put it in the fridge the carbonation level seemed great.

So I am now more confused about to do.

Fortunately my risk mitigation is to finish kegs in 3 weeks

Whether it carbonates or not has nothing to do with purging or not purging

I'm far too stingy to purge a keg with CO2 but I make sure the fill hose goes right to the bottom of the keg. That way, there is no splashing or turbulence after the first litre or so and that is the biggest culprit when it comes to oxygen uptake.

Once again, better than not watching out for it, but not as good as purging. You can splash all you like if there is no oxygen in there, so your technique stops being a critical control point.

Oxygen post fermentation is bad - it is the worst - barring an outright infection - thing that you can do to your beer if shelf-life is a concern. Like I said, you don't "ruin" your beer by not worrying, or worrying less - but naturally carbonated or not - less oxygen exposure is better for your shelf life.

Whether the cost/effort of purging is worth it too you... that might be debatable and I'm not saying anyone is doing it "wrong" - but there really isn't any sensible argument around the fact that reducing packaging oxygen (and purging your keg is one way to do it) is better than not reducing packaging oxygen.

Its all about where you personally decide to draw the line

 

[Brewman_]

Sounds like a discussion between the "best practice" and "fit for purpose". Take your pick.

Just one extra point, CO2 is heavier than O2, so CO2 will naturally fall below O2 and N2 in air. So even if you do not purge your keg with CO2, then the liquid rising in your keg will gently move the air out containing the O2, while at the same time any CO2 that is precipitating from the beer will generally form a layer over the rising liquid, and so mitigate to an extent any O2 dissolving into your beer.

Hey there are risks. There are risks in every step of brewing, but are they acceptable, that's the question.

Fear_n_loath

 

[jyo]

I have been kegging for a few years now, and #1 rule I was told by many was to purge the keg. Because CO2 is heavier than air, you don't need to chuck much in there, so wastage should not be an issue; it sits at the bottom of the keg, and the blanket of gas rises with the level of the beer whilst filling.
I just do it, 'cause I'm a pedantic prick.

Edit, Fear n Loath just covered some of this.

 

[Thirsty Boy]

I have been kegging for a few years now, and #1 rule I was told by many was to purge the keg. Because CO2 is heavier than air, you don't need to chuck much in there, so wastage should not be an issue; it sits at the bottom of the keg, and the blanket of gas rises with the level of the beer whilst filling.
I just do it, 'cause I'm a pedantic prick.

Edit, Fear n Loath just covered some of this.

I think that the blanket of C02 thing is hooey - the level of mixing from brownian motion, let alone the turbulence of gassing, filling, moving the keg etc is enough to completely disrupt it. C02 blankets are folklore rather than fact. Better than nothing I suppose, but hardly worth it IMO.

I'd rather see someone not worrying, than wasting time effort and money on something that is going to be fundamentally ineffective.

Pressurize and release will reduce the O2 in the keg - pressurize to 1 atmospheres (15psi) and vent... half the 02 and halve again each time you repeat. Best practice though is to displace a liquid which will completely remove any non C02 gases.

Once again, its about how much trouble you want to go to - displacing a liquid fits really well with my filter and sanitation process, so its no effort for me. So its what I think is "right" - whats right for you will be different.

 

[Brewman_]

[half the 02 and halve again each time you repeat.

Well that sounds the the way to go.

How many times would you reccomend that you repeat? What is a "safe" level of O2?

Fear_n_Loath

 

[Thirsty Boy]

[half the 02 and halve again each time you repeat.

Well that sounds the the way to go.

How many times would you reccomend that you repeat? What is a "safe" level of O2?

Fear_n_Loath

Back to the "how much gas do you want to waste" thing - if you pressurize and vent, you lose (at 1 atmosphere) 1/2 the O2 .. but also a kegs full of CO2 - and again every time you do it... so its 1/2 - 1/4 - 1/8 - 1/16th... and 80L of C02

The safe level of 02.. is the least you can manage. Less is always better. So for mine, three pressurize/vent cycles minimum and then transfer carefully to minimise picking up the any of whats left (12% ish of the amount you started with) or save yourself the time and don't bother.

However - If you displace a full keg of water or sanitiser you get rid of 100% of the O2 and use maybe 20-22L of C02 - and thats what I would recommend.

A trick if you dont want to have to deal with a full kegs worth of sanitiser, is to use a high foaming no-rinse like starsan - then you can half fill the keg, push gas into the liquid side till it froths - the froth will be 100% full of CO2 and as it rises will push out the oxygen, when foam comes out the pressure relief, then the keg is fully purged. Same thing but you only have to have a container big enough to hold 9 or 10L of sanitiser instead of the full 20ish needed to completely fill a keg.

 

[SpillsMostOfIt]

Just one extra point, CO2 is heavier than O2, so CO2 will naturally fall below O2 and N2 in air. So even if you do not purge your keg with CO2, then the liquid rising in your keg will gently move the air out containing the O2, while at the same time any CO2 that is precipitating from the beer will generally form a layer over the rising liquid, and so mitigate to an extent any O2 dissolving into your beer.

I believe this to be a common home-brewing myth. If it were completely true, we would all die of suffocation on still days and SCUBA gear would be a more common part of a dry caver's equipment.

 

[jyo]

I believe this to be a common home-brewing myth. If it were completely true, we would all die of suffocation on still days and SCUBA gear would be a more common part of a dry caver's equipment.

You are never going to achieve the concentrations of CO2 in the natural environment that you will in a keg. As CO2 only comprises 0.038% of all atmoshephere gases, the possible levels that form a layer of C02 in a cave would be tiny.

C02 is much heavier than air- fill up a balloon from your bottle, and blow one up with normal air and drop them at the same time. What i am getting at is that the concentrations we pump into a keg to form the layer is MUCH higher than that in the atmoshpere, therefore, you are looking at a nice buffer of about 10-15 cm's of gas, which is pleasing to my pedantic mind.
I'm not trying to be a smart arse, SpillsMostOfIt, merely justifying my overuse of gas. :icon_cheers:

Cheers, john.

 

[SpillsMostOfIt]

You are never going to achieve the concentrations of CO2 in the natural environment that you will in a keg. As CO2 only comprises 0.038% of all atmoshephere gases, the possible levels that form a layer of C02 in a cave would be tiny.

C02 is much heavier than air- fill up a balloon from your bottle, and blow one up with normal air and drop them at the same time. What i am getting at is that the concentrations we pump into a keg to form the layer is MUCH higher than that in the atmoshpere, therefore, you are looking at a nice buffer of about 10-15 cm's of gas, which is pleasing to my pedantic mind.
I'm not trying to be a smart arse, SpillsMostOfIt, merely justifying my overuse of gas. :icon_cheers:

Cheers, john.

If the atmosphere is between 11 and 100 kilometres thick (depending on how you define it) and CO2 did drop to the bottom of any container it found itself in, would we not find the lower 4 metres of so of the air we breath significantly more than 0.038% CO2?

I *am* trying to be a smart arse , but I also do not subscribe to the blanket theory. I *do* subscribe to doing whatever works for you though.

 

[jyo]

If the atmosphere is between 11 and 100 kilometres thick (depending on how you define it) and CO2 did drop to the bottom of any container it found itself in, would we not find the lower 4 metres of so of the air we breath significantly more than 0.038% CO2?

I *am* trying to be a smart arse , but I also do not subscribe to the blanket theory. I *do* subscribe to doing whatever works for you though.

I see your point, but we also have trees and algae that pump out O2 at ground/ sea level.

Agree, whatever works. If brewers have no issues with not purging, then brew away happily.

 

[SpillsMostOfIt]

I see your point, but we also have trees and algae that pump out O2 at ground/ sea level.

... and wind and thermal gradients and birds and stuff as we do high-pressure gas bottles that push the CO2 into kegs and stir things up. My real point is that there is enough going on in the gas soup inside your keg that you are unlikely to get any stratification of gas in there unless you leave it for quite a while at a *very* low and *very* constant temperature to settle out - and at that point you've either lost interest in waiting and your beer went off in the fermenter or you burnt your fingers trying to move the keg.

I recall reading somewhere - probably on the interwebs, so it is likely rubbish - that in professional packaging circles, 5% airspace in a beverage bottle is considered okay. At the risk of veering towards the original subject (oh no!!) I wonder *how much* oxygen is required to ruin beer at what rate...