purging kegs

[moreb33rplz]

Back on page 1 somebody (I already forgot who) was making the point that at some point reducing oxygen has diminishing returns. And everyone ignores him, and instead posts graphs and charts of densities and weights and other things that I don't think get to the heart of the matter.

Let's work backwards. The point of reducing oxygen is so the beer tastes as good as it would have on the day it was transferred, for an infinite amount of time in the future.

But nobody has anything resembling data on this. There are anecdotes of 'my beer tastes better' when someone incorporates some aspect of oxygen reduction, but that is pretty meaningless IMO. I don't know you, I don't know how good your beer is, I don't know what your process is.

Generic brewery we all love had a class where they let us taste beers that were at different ages and, lo and behold, the oldest one tasted worse. Slightly more convincing, but still nowhere near 'data'.

What I care about is where is the line where my beers will start to taste noticeably worse in a reasonable time frame that I might drink them.

As far as I know nothing beyond anecdotes (usually provided by folks who are already way deep down the low-oxygen rabbithole) exists to quantify that.

My experience? I do about half my beers uni-tank style, i.e., transfer the wort into a keg, adding yeast, then 2 weeks later putting it on gas and drinking it. I.e., pretty low oxygen exposure. The other beers I make I ferment in a traditional fermenter and then open transfer to a keg.

And I can't tell a damn difference. Ever.

Food for thought.

 

[day_trippr]

I don't see anything edible.

If your opening reference was to @doug293cz's post at the top, it doesn't actually support your posit. It simply says there's a gas dilution curve with a tail. It doesn't suggest trying to purge a keg using CO2 is the optimal solution (indeed, it strongly suggest otherwise, unless one is a CO2 baron)...

Cheers!

 

[doug293cz]

Take a look at the under-side of the typical ball lock lid. The PRV extends down a fair bit, meaning there'd be a bubble under the lid...

Cheers!

Yep. The volume of the bubble has been measured at ~ 3 fl oz. Typical headspace for a "full" corny is about 0.35 gal, or 45 fl oz. Air is 210,000 ppm O2, so 3 oz out of 45 oz works out to 210,000 * 3 / 45 = 14,000 ppm O2 in the headspace. If you do a full liquid purge the ppm O2 due to the bubble is ~920 ppm.

Brew on

 

[Unicorn_Platypus]

Well that's kinda a key thing. All of my dip tubes are full-length oem and have been carefully "formed" (IBM jargon for "bent" ) so they're solidly in the center of their bottom wells.

I was actually thinking about doing some tests regarding liquid purging techniques. For instance, some folks think pushing sanitizer out the PRV on an up-right keg is sufficient, but if you flip a ball lock lid over and observe where the PRV opening is there's a considerable volume below that wrt the lid surface. Ounces, even.

Otoh, I've consistently observed kicked kegs with mere tablespoons of fluid remaining. Significantly less than ounces. Thus when I purge a keg, I rapidly fill it upright through the open lid with a large bore hose from my Star San bucket, then lid it, flip it over, connect the bucket to the gas post, connect a purge line to the beer post, then flush until the purge line runs totally clear while I'm gently rocking the keg +- ~45° from vertical.

I'm convinced this is the most effective way to purge a keg prior to filling...

Cheers!

Couldn't you also do a few purges with CO2 after filling the keg all the way with sanitizer? Wouldn't this get rid of most of the remaining. Your way is better. But this was seems quicker/easier than cutting the gas tubes and filling via buckets rather than the bathtub.

 

[Unicorn_Platypus]

It's hard to do that method when dry hopping.

My method for dry hopping in keg is as follows. Do a full liquid purge as others have described here.

The I hook the CO2 up via the liquid line, keep a small amount of positive pressure ~2-4 PSI, open the lid and add the hops (for safety make sure to pull the PRV before opening lid to release pressure buildup in keg). (note: this involves running a second line with a liquid QD hooked up to gas). Then I close the lid, hook the CO2 back up to the gas line and do 4 full purge cycles @ 30 PSI. This part uses a lot of gas, but hops themselves contain air and I want purge out that O2. Also, make sure to purge the gas lines themselves before dispensing in keg.

I think others who spund beer in keg with dry hops might do even better at eliminating O2 via yeast. I haven't tried that method myself yet.

 

[doug293cz]

Back on page 1 somebody (I already forgot who) was making the point that at some point reducing oxygen has diminishing returns. And everyone ignores him, and instead posts graphs and charts of densities and weights and other things that I don't think get to the heart of the matter.

Let's work backwards. The point of reducing oxygen is so the beer tastes as good as it would have on the day it was transferred, for an infinite amount of time in the future.

But nobody has anything resembling data on this. There are anecdotes of 'my beer tastes better' when someone incorporates some aspect of oxygen reduction, but that is pretty meaningless IMO. I don't know you, I don't know how good your beer is, I don't know what your process is.

Generic brewery we all love had a class where they let us taste beers that were at different ages and, lo and behold, the oldest one tasted worse. Slightly more convincing, but still nowhere near 'data'.

What I care about is where is the line where my beers will start to taste noticeably worse in a reasonable time frame that I might drink them.

As far as I know nothing beyond anecdotes (usually provided by folks who are already way deep down the low-oxygen rabbithole) exists to quantify that.

My experience? I do about half my beers uni-tank style, i.e., transfer the wort into a keg, adding yeast, then 2 weeks later putting it on gas and drinking it. I.e., pretty low oxygen exposure. The other beers I make I ferment in a traditional fermenter and then open transfer to a keg.

And I can't tell a damn difference. Ever.

Food for thought.

Here's an example of the kind of information available about O2 levels that can lead to detectable aging. See page 21 for the pertinent numbers.

Brew on

 

[day_trippr]

Couldn't you also do a few purges with CO2 after filling the keg all the way with sanitizer? Wouldn't this get rid of most of the remaining. Your way is better. But this was seems quicker/easier than cutting the gas tubes and filling via buckets rather than the bathtub.

If you have a bathtub full of Star San to completely submerge a keg, more power to you, but I keep just a 6 gallon reservoir of Star San for such matters

I didn't cut my gas tubes to accomodate my purging process but to give me that much more margin against slightly overfilling kegs.
And it isn't germaine to my purging process given the keg inversion, though it is highly relevant to someone who doesn't invert the keg while purging.

As for "quicker/easier", that's much less important to me than maximizing shelf life. I've been brewing a lot of New England style IPAs over the last two years and as a style they are expensive to brew and extraordinarily susceptible to oxidation. So I'll take the time to do the best I can to fight that.

I recently finished a keg of Treehouse Orange Julius clone that was kegged six months earlier and it was still bright, aromatic and juicy to the last drop. Otoh, I can tell you my first keg of that same recipe two years ago didn't make it a month before it had clearly started browning and was rapidly losing character, all because I did essentially an open transfer. Expensive lesson but well learned...

Cheers!

 

[moreb33rplz]

Here's an example of the kind of information available about O2 levels that can lead to detectable aging. See page 21 for the pertinent numbers.

Brew on

Thank you, interesting stuff! Still far from comprehensive but it's something. I noticed they state that under cold storage they couldn't reliably detect a difference under 4 months, which I think is telling. There are still lots of variables left unexplained (what was the measured DO/TPO, what style of beer, etc). Maybe it's my confirmation bias talking but reading that makes me think that unless you're allowing silly amounts of oxygen into your beer, as long as you store it cold and drink it within a few months you won't notice the effects of oxidation. Generally.

 

[Yesfan]

Take a look at the under-side of the typical ball lock lid. The PRV extends down a fair bit, meaning there'd be a bubble under the lid...

Cheers!

^^ Had to visualize it in my head. I stand corrected.

 

[murphyslaw]

Edit: Nevermind!

 

[day_trippr]

[...][I noticed they state that under cold storage they couldn't reliably detect a difference under 4 months, which I think is telling.[...]

It confirms that cold slows chemical reactions, just as most cases on this particular planet...

Cheers!

 

[doug293cz]

Thank you, interesting stuff! Still far from comprehensive but it's something. I noticed they state that under cold storage they couldn't reliably detect a difference under 4 months, which I think is telling. There are still lots of variables left unexplained (what was the measured DO/TPO, what style of beer, etc). Maybe it's my confirmation bias talking but reading that makes me think that unless you're allowing silly amounts of oxygen into your beer, as long as you store it cold and drink it within a few months you won't notice the effects of oxidation. Generally.

That's no noticeable difference after 4 months of cold storage with significantly less than 1 ppm TPO. Takes a lot of effort to keep things less than 1ppm. And the more O2 present the faster the reactions, even at lower temps.

Brew on

 

[Robert65]

It confirms that cold slows chemical reactions, just as most cases on this particular planet...

Cheers!

Should work on other planets in this universe too, just harder to find a beer there!