Corny Keg causing Off Taste?

[alan@osbornshome.org]

I need help with an off taste in my beer. I recently started brewing again after about a 10 year (!) break. I dusted my equipment off and have 3 batches under my belt. Each of these has a slight astringent metallic bite – drinkable but not right. The first batch was bad enough that I dumped the last several gallons. I do not think it is related to sparging or infection. The cooled wort and beer out of the glass carboy seem ok.

My guess as to the culprit is the corny keg. When I cleaned it before the last batch (I’ve only ever used detergent with one of those green Scotch scrub pads), I noticed a smell when I stuck my nose in – a flat, acrid, metallic smell. Hard to describe. My thinking is that whatever that is, is being leached into the acidic beer as it sits getting carbonated. Do cory kegs develop a patina or some kind of surface scale over that long a period that might be causing my problem? I am about to buy new kegs but maybe there is a cheaper solution. Thanks for any insights!!

[Nyakavt]

If your keg doesn't have any visible scale or rust, the flavor is probably not coming from the keg. Stainless is pretty non-reactive. To be sure you can try a good long soak in hot PBW/oxyclean followed by a good rinse.

Howtobrew says that metallic off flavors can be caused not only by metal dissolving into beer, but also by old malt or by water with high iron levels. I would guess that it could also be overcarbonation, which is something I think tastes metallic. You can check this by swirling the beer around in the glass to release some CO2 and see if the flavor goes away.

As far as astringency, do you mean the puckering mouthfeel like drinking a dry red wine? This would be something else all together, most often from sparging with very alkaline water. Did you check your mash pH/final runnings pH, and do you have a water report?