Wet cloth or dirty cloth smell

Question

I have this problem with my beer and I couldn't find any answer from my friends, experts, or web pages. Following primary fermentation (1 week) I move the green beer to a food grade plastic container inside a refrigerator (25 F). Following a few days of maturation a strange smell (less in flavor) like wet cloth or dirty cloth comes up. I have found this smell in the Brooklyn's Summer Ale, in fact my beer is a summer ale (blond ale) made mostly with pale malt. Parameters: OG 1048 FG 1011 IBUS 20 ABV 4.9%

Answer 1

One thought I have is it's due to incomplete fermentation. Cold crashing a beer after a week will not necessarily make the best beer. Try leaving it in primary for 3 weeks and see if it improves.

Answer 2

As Denny Conn suggests in his response, the simple answer is to leave the beer on the yeast for longer.

During the secondary fermentation stage, the yeast is still working. part of this includes "cleaning up" some undesirable by-products of fermentation. I would guess that it is some of these compounds you can smell.

Dropping the temperature to 25F / -4C will almost certainly make the yeast go dormant. This means they're all falling out of solution, and not finishing the fermentation properly.

In this case, take your beer out of the refrigerator, just the movement might be enough to re-incorporate some of the yeast (do not splash, you don't want more dissolved oxygen at this stage) and leave it for a week. If you don't want to just "leave it", then regularly take a sample until you're happy with the flavours.

It's not necessary to move the beer off the yeast as soon as primary fermentation finishes. It's OK to not even check beers until 2 weeks have past. If you must do it, ensure good sanitation and try to prevent any excess contact with air, as you do not want oxygen in you beer at this stage.

Further Reading: What Happens During Secondary Fermentation