Rusty caramel flavor?

[kwk442]

Here's the details of my brew setup:

• 5 gallon
• All grain, BIAB
• Turkey fryer with aluminium pot
• Plastic bucket fermenter
• 5 gallon corny kegs
• Usually 152 degrees F mash for most recipes

I've brewed about 10 batches with this setup, before which I brewed probably 30 batches on a very similar setup but 2.5 gallon, with some 2.5 gallon corny kegs. Almost all of those batches were very good, but now on the 5 gallon system I've had some issues lately.

On a couple of the batches I've had flavor like rust and caramel, with sometimes a seltzer-like aftertaste? I have 2x 5-gallon corny kegs, the nicer one of which I got first and served several successful and delicious batches from. The other is a little more beat up and the problem started about the time I got it, and then it seemed to happen on a couple alternating batches in a row so I suspected it might be related to the keg. At some point while this keg was on tap recently I also ran out of CO2 earlier than I thought I should -- and when I did, the beer was completely flat, no pressure whatsoever, which makes me suspect a leak, but I did the soapy water test and didn't find anything.

My most recent batch, in the original "good" keg, however, is now tasting a little rust/caramel/seltzer on some pints. Most recently I bottled 6 bottles of a batch and kegged the rest in the "bad" keg so I guess we'll see how the bottled ones compare to the kegged.

I figured carbonation level might be a problem, especially with the seltzer aftertaste. I'd think infection could also cause that but then wouldn't it be super dry instead of caramelly?

If the latest batch does taste different from bottle vs keg I'm tempted to either replace basically the whole draft system (kegs, lines, connectors, tap) or think about bottling again. I unfortunately don't have a lot of measurements because I had such good results on something like 35 batches in a row that my strategy was very RDWHAHB because the results were always very good until just recently.

Does anyone have any ideas or suggestions?

Thanks

 

[oceanic_brew]

You could taste an infection without it having been infected long enough for it to dry out your beer. Some infections take some time at optimal temps to dry out a beer and since you are kegging even if you did have an infection you may be slowing its growth at serving temps.

The caramelly/rust flavor has me stumped. Flavors from infections are usually very distinct (vinous, medicinal, band-aid, sour) I've had 7 due to infected plastic. I know a few of them well.

Could you explain your cleaning and sanitizing process of your kegs a bit?

Other than that it would be a good to make a 5 gallon batch of a brew and split to the two kegs to see if you recognize any differences in the two.

With adequately cleaned, rinsed and sanitized kegs, lines, quick connects, and faucets the beers should taste exactly the same. Provided equal co2 and line length.

It's a cheaper experiment than replacing your entire keg line and then finding that it's one little piece of pre-ferment equipment causing you trouble

At first I was thinking maybe you are mashing a little higher due to bad thermometer but that would more so give you a sweet finish/high gravity rather than a caramel flavor.


Another reason to take very detailed notes. I had to write down all my equipment and mark all my fermenters before I found my sources (auto-siphon and scratched bucket)

 

[oceanic_brew]

Are you getting a lot of scorching on your the bottom of your aluminum pot?

Can't see that giving excessive caramel flavors but I do boil down first runnings in certain Irish reds and Belgians to get a little in un-fermentables which I personally find gives a caramel flavor.


But we are talking boiling 1/2 gallon down to a sludge

 

[kwk442]

For the kegs, I usually throw a pint or so of amberdyne solution (which is apparently iodophor or at least iodine based) into the keg and slosh it around, then remove the keg fittings and throw them in as well. The dip tube is harder but I usually pour some amberdyne mixture down it afterwards.

I'm not aware of scorching.

I tasted another sample just now and it's OK, but not great like this recipe has been in the past. This particular sample does not taste like rusty caramel but it poured foamy and has some seltzer aftertaste. I wonder if I'm just having carbonation problems. I always use the slow boat to China method of force carbonation by just leaving the regulator at my serving pressure of 12 psi.