pH changes in finished beer -- beer got sour, then improved?

[Horseflesh]

I kegged a pale ale last week and experienced something really confusing, hopefully you guys can give me some ideas.

The beer going into the keg from the fermenter tasted great. After about 24 hours under 30 PSI, it was partially carbonated, and tasted overly tart. It was so tart and strange tasting that I got out my pH meter.

The new pale ale was at pH 3.7! My other beers on tap were 4.1 (hefeweizen) and 4.2 (mango wheat).

Unfortunately, I did not check pH of the un-carbed beer at the time I kegged it, but I was in love with the warm, flat sample. If I warmed a tart sample to room temperature, it was not the taste I remembered. I am as sure as I can be that the beer changed after kegging.

I thought I might have had an infection and started a thread asking about overnight souring. I was told that is unlikely, which I expected.

After a few more days of chilling and carbing at 10 PSI, I presumably blew out some more settled yeast and hop specks, and the beer tasted good. The pH is now up to 4.2!

Why would a beer gain tartness after kegging, and then lose it? And this isn't just a perception issue, pH definitely changed.

The only thing that kind of makes sense is hop and yeast residue settled, changed the taste, and taste improved as settled material was dispensed. But I have never had this happen before.

What happened?

Other details that might be important:

- I did adjust the mash water with minerals and some phosphoric acid (thanks Bru'n Water), mash pH was 5.44. I can provide mineral details if needed.

- I don't think I got a good hot break. (New electric system, being conservative while I learn how to not scorch.)

- Yeast was US-05

- Hops were Magnum (60 min bittering) plus Citra and Galaxy. There were about 2 oz late/whirlpool hops and 3 oz dry hops, all pellets. This is the most dry hops I've ever used and the first time I've dry hopped with loose pellets. This is really the only thing majorly different about this beer.

- Transfer to keg was done under CO2 as best as I was able (100% co2-filled keg, siphon from bottom of fermenter to keg out post)

- Beer was NOT cold crashed in the fermenter in an effort to avoid oxygen intake (my first heavily dry hopped beer, trying hard to preserve hop flavors)

- Beer is still very cloudy, presumably due to lack of cold crashing in the fermenter plus possibly a poor hot break.

- Some hop specks and yeast made it into the fermenter, but not what I'd call an unusually large amount.

 

[porterpounder]

Overcarbing beer will lead to an excess of carbonic acid in solution, thus a higher acid reading and some unpleasant tartness can result.

 

[Horseflesh]

I have clumsily overcarbed kegs many times and never tasted anything like this. Per the burst carb chart at Brulosophy, I should have been in a fairly normal range by doing 30 PSI for 24 hours, then down to 10 PSI. (Keg temp was about 37F.)

I thought about carbonation too, when I had my first tart taste. But carbonation can't be to blame. The carbonation level did not decrease, yet beer became less tart, and the pH meter backs that up. It's weird, man.

 

[EJay]

... E pur si muove - Galileo

I think it had to be carbonation. For whatever reason (extra cold temps?) it got more saturation than normal under 30psi, so more carbonic acid, lower pH, and more bite. When you turned down the regulator to 10, it outgassed (or you pulled a pint), and that caused a pressure drop, carbonation to decrease, and pH to rise.

This absolutely fits all the symptoms and measurements.

 

[Horseflesh]

(Nice Galileo reference, heh!)

Since I don't have a way of actually measuring carbonation levels I have to allow that overcarbonation could be the culprit. This just doesn't match my past experiences. I have made very similar beers that I have carbonated in the same way and not had this happen. 30 PSI for 24 hours at 37F should not result in a crazy over-carbed beer.

Hmm. There is one crude way to measure carbonation levels, and that is how the beer pours.

When I first tasted it the tart beer, I was pouring through 8 feet of 3/16 ID beverage line. The tart flavor freaked me out, and so I switched to a picnic tap on about 2 feet of 1/4 ID line... Just to try and rule out something funky in my tap line. In both cases, the beer poured fine, in fact, my perception was it was still under-carbonated. (This was after a day at 30 PSI/37F, but I vented and reduced pressure to 10 PSI for serving.)

According to the carbonation chart, 30 PSI and 37F comes to 4.32 volumes. I am assuming that it was not yet at that level, having only been on for 24 hours. While I don't know what the true carbonation level was, it definitely was not pouring like it was at 4.32 volumes. With 2 feet of 1/4" line, you'd get nothing but foam, right?

I guess this is the bottom line: what carbonation level does it take for a pale ale to taste sour?

I'm honestly not trying to be argumentative. It just seems like some things don't add up.

Unfortunately I did not think to shake the hell out of some of the tart beer to decarb it. Since my carbonation routine was the same as always I had eliminated it early on.

Despite my giant essay here, the only things that kind of make sense are carbonation issues or blowing out something that settled during chilling.

Thanks guys, I do appreciate the conversation.

 

[GotPushrods]

Well it's interesting at least, love a good mystery.

I've never had a de-carb'd beer rise more than maybe 0.10-0.15 so let's just say you would have read 3.80-3.85 ish de-carb'd. Still low for US-05. Just for fun I went back through my notes.... lowest finish for US-05 I ever had was 4.10 on an APA.

All of this assumes a properly calibrated meter of course. I've always read of carbonic bite but never experienced it. My gut tells me that would have to be way over carb'd which this does not appear to be.

My first reaction was a dirty line from that first low-pH pour, sounds like maybe you discounted that.

I've also never seen stratification in terms of pH but that doesn't mean it couldn't happen.

Generally your pH will be stable after packaging unless it goes down due to infection or up due to autolysis.

How many pours were sour? Just one? Is it possible you had some StarSan in the liquid-out tube contaminate the first pint?

 

[Horseflesh]

Yeah, I think I eliminated dirty lines by putting on the picnic tap.

Here's the sequence of tasting events...

Weds: Kegged, tasted great warm, put on at 30 PSI/37F
Thurs: Reduced pressure to 10 PSI, tasted--too tart. pH 3.7. Went through between 1-2 pints over a few hours, futilely tasting a few ounces at a time. "Try it now!"

[ame]https://www.youtube.com/watch?v=rryQfAnQs3M[/ame]

Fri-Sat: Left it alone
Sunday: Blew out another pint or so. Tried it again. Tastes good, pH up to 4.2.

Weird.

EDIT: Lame that it embedded the video, it was supposed to be a link.

 

[Horseflesh]

Update: A few more days have passed and the beer has improved some more. On Sunday there was a tiny bit of tartness that I didn't expect, though it was totally in line with other pale ales I tried. Today, 4 days later, I can't detect any tartness, and it's finally the pale ale I had in mind.

Carbonation has been increasing, too. After its 24 hour stay at 30 PSI it was not fully carbed, that just kickstarted it. It's taken until now at 10 PSI to equilibrate.

So, whatever was going on, I am 99% sure it wasn't related to carbonation... though I struggle to think of any other process that accounts for this either.

 

[ajdelange]

No, it wasn't carbonation. A couple of volumes will only change the pH by about 0.1.