[euge]

I brewed two porters, at the same time with the only variation being one was with 60L and the other with 120L. Same yeast same temp. Kegged at the same time. Force-carbed samples were both good. Conditioned for nearly a month.

The 60L tastes great- like it's sample. The 120L taste is harshly metallic and undrinkable in complete contrast to the sample. BTW let me mention that when I mean "sample" I mean at least a liter if not more. Usually more. So I had expectations for this beer.

Referring to HTB I got "unprotected metals" or "hydrolysis of poorly stored malt".

Ideas?

[tschmidlin]

Dirty keg?  Or a somehow defective part in the keg?  Scratched surface, something like that maybe.

When did you have the samples, right away and then a month later one was bad?  If so, its something that happened after, so I would lean toward either a problem with the keg or a possible contamination.

Which did you rack first?  Where are possible sources of copper and iron in your brewery?  Apparently a little bit of metal can get worse over time, according to two master judges I spoke to recently.

[euge]

Well I do use a copper tube to weigh down the hose when I keg. Could the pH of the 120 be that different- enough to leach and cause the off-taste? I think the 60 was racked first but it only took minutes.

I also leaned towards contamination- would oxyclean exhibit this?

[tschmidlin]

I don't use oxyclean (but I use pbw) so I can't say for sure, but everything is always well rinsed.

It is entirely possible that the copper piece is the problem.  Not the ph of the 120 most likely, but maybe the 60 stripped off some of the protective coating and the 120 was picking up copper.  Beers I've had that had a piece of copper pipe stuck in them for 45 seconds were noticeably bad after 7 days.

Have you ever racked batches back to back like that before?

[euge]

Oh yes. Many. Good to know about the copper. I won't be using that again. Interestingly, the last bit- 2 liters of the 120, was racked into a bottle that sat in the fridge until a couple days before I tapped the keg. It was fine with no metallic flavor. A bit of acetaldehyde but I expected that.

Maybe contamination? Also, I'm going to drain off a quart or so and and see how it tastes then.

[tschmidlin]

Yeah, it could very well be contamination, especially since you've done it with lots of 5 gallon batches back to back.  One of the judges commented that he didn't start scoring really well with his beers (like winning BOS) until he removed all copper and brass from his post fermentation bits.  His counter-pressure filler for one, now it is all stainless.  He wins a lot of medals.

[euge]

Now I feel like a dipsh!t since it doesn't taste metallic anymore. Umami to be sure. I'm wondering if it was any residual "matter" cause the beer is clear.

Something that had settled out? In the yeast perhaps?

[tschmidlin]

Sure, maybe.  It's always good to judge the third or fourth pint from the keg, not the first couple if stuff will be settling out.

[mabrungard]

Was there a significant difference in the predicted beer color between the beers?  If there was, then the pH effect might have had a minor influence.  But since both the 60 and 120L are crystal malts, their acidity slope is similar and if the beer color for the beers is similar, then the overall acid contribution from the grain should have been similar.

[dak0415]

Well the good news is....the 2nd keg doesn't suck anymore!
What hops were you using?  Any Phoenix?

[euge]

I designed them to be the same SRM so there was less 120 than 60 in the respective recipes. I'll do a color and pH test later today.

And since I've managed to lose the notes my memory tells me Goldings and Cascade. I used Windsor yeast and fermented in the mid 60's.

I'm leaning towards it being whatever's settling out and is in the bottom of the keg. And what is the term for that? Sediment? Haze? Yeast bite?

[euge]

And...

I just did a side by side comparison. Color and clarity are the same (20 SRM) as well as pH= 4.3. I measured the pH at serving temp and will measure it again at room temp when I get home later tonight.

Edit: The pH remained 4.3 at room temps.