Kegged beer issues

[aarong]

Im trying to hunt down an issue with my kegged beers. I bottled half of my last two batches and my kegged beer and bottled beer tasted way different. The bottled beers were crisp and had no discernible off flavors.

My kegged beer on the other hand turns almost creamy tasting and the flavors taste muddled. It is definitely not crisp and just tastes off.

I have taken apart my taps to clean them and run PBW through the lines between kegs.

To keg the beer I attach silicone tubing to the spigot on my fermentor and pour into the bottom of the keg. I then purge the head space a couple of times.

Has anyone had a similar experience? Any help would be appreciated.

Aaron

 

[Gonefishing]

You don't put CO2 in the keg before you keg it?

 

[aarong]

No, I don't. That sounds like it could be my issue.

Do you just pressurize with CO2 and purge it a few times before filling?

 

[doug293cz]

Fill the keg with StarSan and push out with CO2. Then do a closed transfer from your fermenter into the beer out post of the keg with the PRV open. For extra credit, leave the PRV closed and feed a line from the CO2 post back to your fermenter, or push out of your fermenter with low PSI CO2.

A couple of purges with CO2 won't do the job. The table and chart below show how much O2 is left in the headspace after various numbers of pressurize and vent cycles for several different CO2 pressures. Commercial brewers target 0.1 - 0.2 ppm total packaged oxygen, So you can see what it takes to get down there.





Even with liquid pre-purge of the keg you still have too much O2 in the headspace. Due to the lid design, if you fill until the StarSan comes out the PRV and CO2 post, you still have 3 fl oz of air trapped in the lid cavity. A keg has a total volume of about 5.3 gal, or 680 fl oz. So, after pushing the StarSan out of the keg, you still have:

210,000 ppm O2 * 3 / 680 = 925 ppm O2​

It'll take you about 8 purges at 30 psi to get below 1 ppm O2 in the headspace.

It's possible by cutting down the gas "dip" tube so it doesn't stick below the gas post fitting, and then tilting the keg just right when filling with StarSan, to get all of the air out of the keg initially. You naturally want to make sure that your racking tubing, etc. is CO2 purged as well, so you don't introduce additional CO2 during racking.

Brew on

 

[Gonefishing]

Damn, Doug, that's some good info! I've always only run CO2 into the keg for like 20 seconds and then siphoned in with the lid open....I think I'm done doing that.

 

[aarong]

Yea this is great info. I'll give the starsan push a try as well as purging the head space more. Thanks again!

 

[Smellyglove]

Where is this table from? Did it take account for air having 21% o2? (i know it says 02, just want to double check).

If this is correct that's great information. Bookmarked for future personal reference.

Can anyone provide the math calculating how much o2 will end up in the beer? Just a formula, i suck at maths... For instance if you have 1dm3 or 2dm3 of air inside the keg (which is a lot yea, but just for the math). Is it henrys law?

 

[Metzen]

Fill the keg with StarSan and push out with CO2. Then do a closed transfer from your fermenter into the beer out post of the keg with the PRV open. For extra credit, leave the PRV closed and feed a line from the CO2 post back to your fermenter, or push out of your fermenter with low PSI CO2.

A couple of purges with CO2 won't do the job. The table and chart below show how much O2 is left in the headspace after various numbers of pressurize and vent cycles for several different CO2 pressures. Commercial brewers target 0.1 - 0.2 ppm total packaged oxygen, So you can see what it takes to get down there.

View attachment 411143

View attachment 411144

Even with liquid pre-purge of the keg you still have too much O2 in the headspace. Due to the lid design, if you fill until the StarSan comes out the PRV and CO2 post, you still have 3 fl oz of air trapped in the lid cavity. A keg has a total volume of about 5.3 gal, or 680 fl oz. So, after pushing the StarSan out of the keg, you still have:

210,000 ppm O2 * 3 / 680 = 925 ppm O2​

It'll take you about 8 purges at 30 psi to get below 1 ppm O2 in the headspace.

It's possible by cutting down the gas "dip" tube so it doesn't stick below the gas post fitting, and then tilting the keg just right when filling with StarSan, to get all of the air out of the keg initially. You naturally want to make sure that your racking tubing, etc. is CO2 purged as well, so you don't introduce additional CO2 during racking.

Brew on

How do you define a purge cycle? I.e. Is it a quick pull on the PRV? Etc?

 

[doug293cz]

Where is this table from? Did it take account for air having 21% o2? (i know it says 02, just want to double check).

If this is correct that's great information. Bookmarked for future personal reference.

Can anyone provide the math calculating how much o2 will end up in the beer? Just a formula, i suck at maths... For instance if you have 1dm3 or 2dm3 of air inside the keg (which is a lot yea, but just for the math). Is it henrys law?

It's from a spreadsheet I created that uses simple dilution math, the ideal gas law (PV = nRT), and assumes complete mixing of the air and CO2 in the headspace after pressurization. The dilution at each purge cycle is:

New O2 Concentration = Old O2 Conc * 14.7 / (14.7 + P)
where P is the gauge pressure​

Final O2 concentration is given by:

Final O2 Conc = Original O2 Conc * (14.7 / (14.7 + P)) ^ N
where N is the number of purge cycles​

Yes, notice at 0 purges that the O2 concentration is 210,000 ppm, which is 21%.

The absorbed O2 will approximately follow Henry's law, but as the O2 in solution reacts with components in the beer, O2 concentration will go down, so to maintain equilibrium, more O2 gets absorbed from the headspace.

Brew on

 

[doug293cz]

How do you define a purge cycle? I.e. Is it a quick pull on the PRV? Etc?

A purge cycle is pressurizing the headspace to the target pressure, and then releasing the PRV until the headspace pressure returns to atmospheric pressure (i.e. 0 psi gauge.) On both the pressurize and vent parts of the cycle, wait until you hear no more gas movement before closing the valve.

Brew on

 

[HausBrauerei_Harvey]

Saw this thread come up in another thread. I use a slightly different method for the initial purge of the headspace that I wanted to put out there.

Step 1) I rack to an open keg, then close the lid. (I dont even fill the keg with CO2 before the rack).
2)I open the PRV and then turn on the CO2 and let it flush the O2 out of headspace for a good 5-10 seconds.
3) I then do 8-10 purge cycles at 12 PSI.

obviously the flush step (step 2) will help flush the initial air out of the headspace pretty well, and when you close the PRV prior to purge cycle 1 you've now got a mostly CO2 atmosphere in the headspace. This combined with a few purge cycles likely gets me to pretty low O2 levels. I have not noticed any signs of oxidation on my beers, nor have some BJCP certified members of my club. several times I have had friends/acquaintances tell me after visiting my place, upon subsequent visits to some local brewery they will comment that my beer is better than the local breweries, so I doubt it's my personal bias saying "my beer is great with process X"

It might not be the perfect method but it works for me to make great beer with a really simple process.

 

[CudaJoe]

Ive never had the kind of trouble with oxidation that is being described in this thread. I've always siphoned into a keg (open) thats been pressurized with CO_2.. close the lid, add target CO_2 pressure and purge 6-7 times. My beers have been fine.

 

[Smellyglove]

Ive never had the kind of trouble with oxidation that is being described in this thread. I've always siphoned into a keg (open) thats been pressurized with CO_2.. close the lid, add target CO_2 pressure and purge 6-7 times. My beers have been fine.

Not to bash on you. But I bet your beers could have been even finer.

This is in general. Lots of homebrewers feel their beers are good, or even excellent. And when they are judged they are smashed. Very often (where I live) due to oxidation. I was at a homebrewers meeting a few months ago. And we tasted lots of samples. I think I tasted about 14-15 samples. All of them were a beer the brewer was very happy with. "the best I've brewed, my favourite so far" etc.. All of them, and I mean ALL of them were quite bad. It was either due to bad fermentation temp-control or oxidation.
I must add that my local homebrew-community are mostly novices, they have just started brewing. But, I feel that many people feel that "since it's homebrewed, it's great!"

They key to brew good beers are sampling great beers, all the time. So the samples are the references. And you must be picky on your samples. I live in Europe, so I don't buy IPA's which are from the US, due to the deterioation of the beer during shipping. Most of the bottled US IPA's are totally wrecked when I get my hands on them. But If the references are skewed (like if I'd buy an IPA on bottle from the states) then I wouldn't know how a proper IPA is supposed to taste, and my own beers are comparable when it comes to quality, even though both are very lacking when it hits your glass

 

[doug293cz]

Saw this thread come up in another thread. I use a slightly different method for the initial purge of the headspace that I wanted to put out there.

Step 1) I rack to an open keg, then close the lid. (I dont even fill the keg with CO2 before the rack).
2)I open the PRV and then turn on the CO2 and let it flush the O2 out of headspace for a good 5-10 seconds.
3) I then do 8-10 purge cycles at 12 PSI.

obviously the flush step (step 2) will help flush the initial air out of the headspace pretty well, and when you close the PRV prior to purge cycle 1 you've now got a mostly CO2 atmosphere in the headspace. This combined with a few purge cycles likely gets me to pretty low O2 levels. I have not noticed any signs of oxidation on my beers, nor have some BJCP certified members of my club. several times I have had friends/acquaintances tell me after visiting my place, upon subsequent visits to some local brewery they will comment that my beer is better than the local breweries, so I doubt it's my personal bias saying "my beer is great with process X"

It might not be the perfect method but it works for me to make great beer with a really simple process.

The drawback to your method is that there is no way to figure out how much residual O2 you actually have. Whereas there are relatively simple methods that let you know with pretty good certainty what the final O2 content is. Your hobby, your choice, but personally I prefer deterministic methods where available.

Brew on

 

[CudaJoe]

Not to bash on you. But I bet your beers could have been even finer.

This is in general. Lots of homebrewers feel their beers are good, or even excellent. And when they are judged they are smashed. Very often (where I live) due to oxidation. I was at a homebrewers meeting a few months ago. And we tasted lots of samples. I think I tasted about 14-15 samples. All of them were a beer the brewer was very happy with. "the best I've brewed, my favourite so far" etc.. All of them, and I mean ALL of them were quite bad. It was either due to bad fermentation temp-control or oxidation.
I must add that my local homebrew-community are mostly novices, they have just started brewing. But, I feel that many people feel that "since it's homebrewed, it's great!"

They key to brew good beers are sampling great beers, all the time. So the samples are the references. And you must be picky on your samples. I live in Europe, so I don't buy IPA's which are from the US, due to the deterioation of the beer during shipping. Most of the bottled US IPA's are totally wrecked when I get my hands on them. But If the references are skewed (like if I'd buy an IPA on bottle from the states) then I wouldn't know how a proper IPA is supposed to taste, and my own beers are comparable when it comes to quality, even though both are very lacking when it hits your glass

I have brought my beer to homebrew club meetings and recieve much praise for them, I can't tell you if they are novices or experts but some of them had been brewing for 30 years. I can promise you I have not had oxidized beer come out of my equipment, not like a keg that was tapped with an air pump and the next day someone trys drinking it.

I usually go out and buy a variety of similar beer styles to the beer I brew and use them as a comparison. For instance, I bought 12 single bottles of Fest biers and Oktoberfest/ Marzen style beers for my latest batch (an Oktoberfest). I use them as a comparison tool to what I make. If it tastes better than a commercial made brew, I am happy. So far I've had some pretty aweful commercial oktoberfest beers.. Some are good though, the ones that are terrible are the companies trying to make their recipe unique and full of flavor (too much going on).

My comparison bottles so far. Dominion and Erdinger are my favorites so far. Flying Fish OktoberFish is terrible.