Is my CO2 system Ruining My Beer?

[Shipdit]

First, I will acknowledge that everyone thinks I am crazy, but here goes...

I have brewed close to 50 all grain batches in the last two years, and have had consistent success from brew day through kegging. However, I have had a nunmber of recent batches (4 of the last 9) that have tasted great when going from primary to secondary, even better when going from secondary to keg, but then develop off-flavors during carbonation. I would describe the flavors as metallic or astringent, or like there is a bitterness present that is not a hops bitterness, but a rather unpleasant one.

At first I thought it could be carbonic acid, so I started force carbing for a longer period at a lower PSI rather than a higher PSI for 2-3 days. This did not address the issue.

I have been trouble shooting for months, trying to isolate the offending variable, and have even gone so far as to replace my CO2 tank, regulator, and splitter. People have told me that this equipment cannot be the culprit, as no unfriendlies would be able to survive in the presence of CO2. If this is the case, can anyone think of another explanation for what might be happening here? I am militant in my cleaning and sanitizing practices, and have even replaced my beer lines. I'm running out of options, and would appreciate any advice!

 

[PlexVector]

Are you using glass or plastic fermentors? especially the secondary--are they plastic and 1+ years old?

BTW: Aren't we all just a tad crazy--some just more than others.

 

[Takuie]

Just a shot in then dark, but may help. I had a similar metallic taste in one of my batches after kegging, barely noticeable but it was there. Noticed it again when using that same keg on another batch. Bought it off Craig's list, cleaned it with PBW then sanitized. It seemed the over mixture of PBW did something to the pickup tube. Replaced tube and pin locks, haven't had the problem since.

 

[TallDan]

Are you just overcarbonating? What temperature and pressure are your kegs at?

How about the kegs themselves? cleaned well? Can you smell anything off in them after they're cleaned?

 

[Shipdit]

Thanks everyone for the quick responses.

I use a bucket for primary, and glass for secondary (I failed to mention it in my original post, but I have replaced my buckets as well). Any time a keg gets kicked, I immediately clean it and the beer line thoroughly to ensure no residual beer has a chance to dry in them. I force carb at about 10 PSI for 4-5 days and lower it to 5 PSI or so once carbonated. I don't have a thermometer in the refrigerator, but I would estimate it to be around 40 degrees. I contend that my kegs are clean, but maybe I should give them all a hardcore scrubbing to be sure.

 

[hunter_le five]

I force carb at about 10 PSI for 4-5 days and lower it to 5 PSI or so once carbonated. I don't have a thermometer in the refrigerator, but I would estimate it to be around 40 degrees.

Why are you lowering the PSI down to 5?

 

[beernutz]

Have you tried naturally carbonating a batch to see if anything changes? If you do 10 gallon batches you could naturally carbonate one keg and force carbonate the other.

 

[BadWolfBrewing]

How about just filling a keg with water and carbing it up for a while, see if the off taste is there too

 

[Eh_Modern_Drunkard]

Are you purging your kegs before transferring? My other question is, what styles are you making? I used to get that a bit with my stouts until I overhauled my methods and techniques.
Also, some "unfriendlies" can most definitely survive a co2 rich environment. I sanitize any piece that comes into contact with my kegs.

 

[Shipdit]

I should clarify - all of my equipment that touches the beer is sanitized. The CO2 tank, gas lines, and splitter are not. The styles that have been affected were all pale ales or IPAs, but I have also had some IPAs that came out fine.

 

[Shipdit]

How about just filling a keg with water and carbing it up for a while, see if the off taste is there too

That's a pretty good idea.

 

[Shipdit]

Why are you lowering the PSI down to 5?

I am trying to avoid over-carbonating - would you recommend just leaving it at 10?

 

[hunter_le five]

I am trying to avoid over-carbonating - would you recommend just leaving it at 10?

It sounds like you're just kind of picking pressures arbitrarily (forgive me if I'm assuming too much). I would recommend consulting the handy-dandy force carbonation chart.

At 40°F, 10-PSI puts you at 2.30 volumes, which is perfectly fine for most beer styles.

When you drop it down to 5PSI, the beer is going to start off-gassing slowly until it reaches equilibrium at 1.83 volumes (undercarbed for most styles, on the low end for stouts/porters).

I am wondering if this sudden reduction in pressure and resultant off-gassing may be contributing to the carbonic bite taste you are experiencing?

 

[PlexVector]

I should clarify - all of my equipment that touches the beer is sanitized. The CO2 tank, gas lines, and splitter are not. The styles that have been affected were all pale ales or IPAs, but I have also had some IPAs that came out fine.

When you sanitize the kegs does this include disassemble of the gas & liquid posts?

Before I connect the gas or liquid QD to the keg I give the post and inside of the QD a quick squirt of sanitizer.

 

[PlexVector]

How about just filling a keg with water and carbing it up for a while, see if the off taste is there too

Great idea!

I should clarify - all of my equipment that touches the beer is sanitized. The CO2 tank, gas lines, and splitter are not. The styles that have been affected were all pale ales or IPAs, but I have also had some IPAs that came out fine.

I've reread this thread several times trying to tease out any subtleties:
-- What sanitizer are you using?
-- Did you get a new bottle of acid base sanitizer when this started happening and it is defective?
--The water used for your sanatizer has changed and is buffering the acidity?
-- The spray bottle?
-- The sanitizing bucket is dirty?
-- what hose connections are you using?
-- Dead bug debris is trapped in a connector, keg post, QD, Valve, chiller, dip tubes, racking cane...?
-- There is a fan running in the brew area that used to not be there?
-- You now mill your grain?
-- Your equipment is stored differently?

Sorry, I'm brain storming and hope you get a ah-ha moment!

What have I missed?

 

[Shipdit]

I do disassemble, wash and sanitize my liquid in an out posts, and spray my disconnects with StarSan before connecting them to the keg. I even use bottled water to make my sanitizer solution, which speaks to how obsessed I have been about diagnosing this issue.

I don't mill my own grain but seeing that my wort/beer tastes great every step of the way until carbonating, I don't think there is an issue with any of my mashing, brewing, or racking equipment (though that hasn't stopped me from replacing several pieces).

I appreciate everyone weighing in, and welcome your continued input. I kegged two 5 gallon batches last night - a Maibock and a Citra session IPA - and will let you know how they turn out in a few days!

 

[dcrog]

Put a thermometer in your fridge. I might be colder than you think which could over carb it at 10 psi.

Or your gauge could be off.

 

[PlexVector]

Or tectonic plate movement has moved an old Indian burial site under your house. Oh, sorry, I think I have run out of ideas.

Good luck with those new batches.

 

[goingcamping]

You guys will forget more than I'll ever know about brewing...

So, here's an uneducated shot in the dark! If 4 out of 9 batches had this taste, have you looked at your water source? Maybe there's a mineral/additive that could survive the boiling and fermenting, but rear it's ugly head during carbonation?

After reading your post, you're obviously very, very thorough with parts and pieces?

Just my $.01 worth!

Cheers,

~Brett