Help figuring out off flavor?

[damdaman]

So I switched to BIAB all grain about 8 batches ago, and for the most part, the quality of all my batches improved dramatically. However, I have an oatmeal stout and Jubelale clone that I brewed on the same day that are now ready for drinkin' (based on my usual time-table of 3 weeks primary, 3 weeks bottle conditioning), but both batches have a distinct off-flavor. It doesn't completely ruin the beer, it's drinkable, but somewhat unpleasant. I also felt like I detected this same off-flavor in a pale ale I brewed after these two, but subsequent tasting during gravity readings I didn't detect it. That batch is now bottled so in a couple weeks I will know for sure.

Anyway, the beer seems pretty well carbed, yet the mouthfeel is flat. There's kind of a sharp twang that hits the tongue early, and then I can taste the delicious oatmeal stout flavors I'm expecting (but with poor mouthfeel), and then there's this metallic aftertaste that lingers for a looooong time.

I use stainless steel pots. The oatmeal stout used Nottingham fresh from the packet, the Jubelale a washed 1056 from a pale ale. Temps were good for all of fermentation (65-70). Because I use BIAB I've been using a really fine grain crush.

Any ideas? Will this improve with more age?

 

[mrk305]

I made an oatmeal stout that was also not good. I think my mash temp was too high. Someone posted a link to an off flavors chart and I saved it as one of my favorites.

http://www.winning-homebrew.com/off-flavors.html

 

[damdaman]

Thanks, one thing in that link you posted caught my eye:

When stainless steel is cleaned without passivating the surface (oxidizing to produce a layer of protective oxide on the surface) the unprotected steel can also cause off flavors.

Lately, my pots have developed this thin layer of something at the bottom of the pot, it's light brownish/reddish in color and damn near impossible to scrub off. I can get portions of it off if I go nuts with a hard scrubby.

Could this be the culprit? Either the build-up itself is causing this metallic flavor, or my attempts to scrub it out of the pot is?