Good Beer Gone Bad in Keg

Hello Everyone.

In the spirit of keeping this question simple. Let me start the story with a perfectly tasting cold crashed APA still in the fermenter.
After 3 weeks of a primary fermentation, 4 day dry hop and 1 day Cold crash the 35 degree beer was sampled and auto siphoned in the keg. The beer was great at this point.

Packaging: I used starsan in the corney keg, poles, tip tubes and on the auto siphon. The keg was not purged with CO2 prior to filling but after filling with beer I purged with CO2 via gas in port and burped with the PRV 3 times. There was 4.7 gallons in the keg.

As this point I very much enjoyed to taste of the APA. May be slight green flavor but hops and the malty backbone was very present

Carbing: After sealing up the keg, and purging with CO2. I did the “patented” quick carb method (rolling/shaking the keg while on the gas). This got the beer carbed 80% of the way in 10 minutes. Pulled some beer from the tap to taste.

At this point the beer tasted as you would expect a young under-carbed beer to taste. No glaring off flavors but needs time to improve.

2 days later: I decided to try another sample off the keg. Oh no. Something isn’t quite right. The hoppy and Malt flavor are dominated by the green apple, tart flavor most likely Acetaldehyde.

I read here: http://www.winning-homebrew.com/acetaldehyde.html
The oxidized or acetic-cider version is produced when ethanol oxidizes, or sometimes from bacterial contamination. It is produced when ethanol is oxidized back to acetaldehyde, and then the acetaldehyde is converted to acetic acid. To prevent this type of off flavors, keep oxygen exposure to a minimum.

I can’t imagine any bateria could ruin beer stored at refrigator temps in two days so I have to think this might be an oxidation related off-flavor. Perhaps this is related to the “patented” quick carb method while failing to purge all of the O2 out of the keg.

Any thoughts?

Acetaldehyde will age out if you keep the beer warm enough for the yeast to do their thing. You could also be experiencing carbonic bite, which is just carbonic acid in the beer from CO2. You forced a lot of CO2 into the beer in a short amount of time, give it a bit of time and allow it to mellow out.

I can't speak to your actual cause scientifically, but I will reccomend weening yourself off the quick carb method. Slow addition of CO2 has improved my beer. If you did have any oxygen, you shoved it right in your beer. Also, make sure your lines are clean. Really clean. I went too long with out cleaning out my lines with actual line cleaner and it caused problems. Occasional star san rinses is not enough.

I wonder if the "two days later" sample was packing extra yeast bite due to the beer having some time to settle out after the shake'n'bake carb thing...

Cheers!

Two things -

1. Check for contamination/mold in the poppits and under the orings on the posts.

2. Be sure it's not your lines. Does the first beer taste different than the second immediate pint?

Just a remark: lines/hoses and keg fittings are best kept in alcohol, not dry, like hanging on the walls or sitting in drawers. 70% alcohol would be the best but in storage terms time matters more than strength, so a week in vodka would very probably kill anything potentially dangerous. And your hoses are always ready to go without additional sanitation.
If this is impractical in your situation, consider pouring some stronger-than-vodka alcohol into the hose, then coiling it so that part of this alcohol gets into the fitting and stays there.

could be carbonic bite or yeast not settled out yet as stated.Force carbing takes a few extra days to settle down and come together.I would let it be for 4 or 5 days and report back.Also when racking be sure to keep the auto siphon tube in the bottom of the keg with no splashing to minimize ozidation

You could also be experiencing carbonic bite

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I think that is it. The "Shake and Bake" carb method might of got me in trouble here along with the colder than appropriate serving temp (from cold crashing). I perceived the bitterness as being something tart since might of over carbed the beer.

packing extra yeast bite due to the beer having some time to settle out

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This was probably the case and didn't help with troubleshooting this observation.

To test if this was just carbonic bite I pull another sample and let it warm up to serving temp and stirred it to knock out some of the CO2. I tasted it and it was almost what it tasted like from day one.

I will reccomend weening yourself off the quick carb method

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I agree. I have been able to fix most of my practices with brewing but patience has not been one of them. Patience is a virtue.

hylander0 said:

I have been able to fix most of my practices with brewing but patience has not been one of them. Patience is a virtue.

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If you are in a hurry try 35 to 40 psi for 24 hours. Vent the keg and knock it down to serving pressure. That will get you most of the way there, a day or two later at serving pressure and you should be good. Not personally a fan of shaking a keg to get carb'd in 20 min, never seems to end well.

I'm suspicious of the "purging" of the keg with CO2. I don't think 3 "burps" of the PRV is nearly sufficient. A fellow poster here on HBT recently ran the numbers and demonstrated that you'd actually need 11 "burps" at 30 psi to reduce residual O2 in the keg to below an acceptable threshold to stave off oxidation. 3 pops at 10 psi is going to leave a lot of oxygen in the keg (which you then immediately shook into your beer). I'm blaming oxidation due to an insufficient CO2 purge of the keg, followed by a burst carbing procedure.

kombat said:

I'm suspicious of the "purging" of the keg with CO2. I don't think 3 "burps" of the PRV is nearly sufficient. A fellow poster here on HBT recently ran the numbers and demonstrated that you'd actually need 11 "burps" at 30 psi to reduce residual O2 in the keg to below an acceptable threshold to stave off oxidation. 3 pops at 10 psi is going to leave a lot of oxygen in the keg (which you then immediately shook into your beer). I'm blaming oxidation due to an insufficient CO2 purge of the keg, followed by a burst carbing procedure.

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Yep. I was going to post here earlier, but then OP said the taste seems to be improving with a little more aging, so the original taste issue is not likely oxidation. But, given the low number of purge cycles plus shaking, OP may have oxidation issues soon enough.

Just so folks don't have to search for the "how many purges do I need?" posts, here is the info:





Commercial brewers have found that 0.15 ppm of O2 in the beer is sufficient to cause detectable oxidation with 3 weeks of aging at room temp (see page 21 of http://www.craftbrewersconference.com/wp-content/uploads/2015_presentations/F1540_Darron_Welch.pdf.)

To calculate the headspace contribution to TPO use the following formula:A 5 gal ball lock keg has a total volume of about 5.3 gal. Since OP's beer volume was 4.7 gal, headspace volume was about 0.6 gal. If OP did 3 purges at 10 psi, then the TPO contribution, just from the headspace, is:If purges were done at 30 psi, then the TPO contribution is:Too much O2 in either case.

Brew on

OP may have oxidation issues soon enough

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You are right. I suspect, however, it may be long gone before it creeps in. Let the race begin

If OP did 3 purges at 10 psi, then the TPO contribution, just from the headspace, is: 5011 ppm

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That is fantastic information.

Also, I read this: If CO2 is so heavy, why doesn't it sink and suffocate us? This explains in principle that CO2 blankets is really a misnomer.

Sounds to me when you "purge" aren't getting rid of other gases in equal amounts. Also you aren't placing a barrier of CO2 between your beer and O2.

So purging is really just diluting the atmosphere gases with CO2.

Does anyone know how the commercial breweries combat this problem with kegs? Do they just do a brute force purge to get their PPM below their threshold before and after filling?

The description of his off flavor doesn't sound to me like oxidation, though it may also be of concern. I also don't know that numbers of burps is at all an accurate way of determining the removal of oxygen. If one person burps the keg it could be very different than the next person. Do you open the valve for a fraction of a second or for a second or two or three??? for each burp??

I would go with yeast stirred up and carbonic bite.

kh54s10 you are correct. It was determined to be carbonic bite/carbonic acid.

However, The purge burps where not enough per doug293cz's posting. In a short enough time the beer will start to oxidize.