Author Topic: Moldy tasting beer  (Read 3678 times)

Offline thomasbarnes

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Re: Moldy tasting beer
« Reply #15 on: June 27, 2011, 01:58:13 PM »
I need a wort cooler, and I should probably be brewing in my basement ... but, I waited too long to turn on my dehumidifier and it has gotten moldy down there.  WHile I am working on it and have my dehumidifier on, it was a bit late for my last few beers. 

It's relatively easy to make an immersion wort chiller.

Once the dehumidifier gets the mold levels knocked down, if the basement is still musty, you might need to scrub the walls and floor with dilute bleach or fungicide. If it's only slightly musty, it's probably OK to brew there as long as the air is relatively still (i.e., not a whole lot of dust in the air or temperature swings) and you keep any plastic fermenters off the floor (a pallet is good).

That being said, I am surprised that the higher temps would have created this particular funny flavor, I would have though more butterscotch.

Butterscotch and green apple (diacetyl and acetaldehyde) might be products of high temperature fermentation, but they're more typically a sign of poor or stuck fermentation since the yeast scavenges those products up as fermentation winds down. The classic "fermented too hot" off-characteristics are solventy, harsh "higher" alcohols and various phenols - smoky, medicinal, plasticy and/or spicy notes. Your "moldy" character could very well be due to phenols, since some smoky notes can be interpreted as being "peaty" or "earthy."

However, I do think think the best explanation for all of this is that the high temps, the long sit in the yeast, combined with the pine created a horrid tasting beer ... for now at least.

Even with a relatively high temperature fermentation, I don't think that yeast had too much to do with the off-flavor. Autolyzed yeast doesn't taste moldy, so much as "brothy" or like a vitamin B pill. If you've ever tasted nutritional "brewers yeast" or Vegemite or Marmite, it's like that flavor. More to the point, autolyzed yeast character takes weeks or months to develop.

My guesses as to the off flavor are:

1) Spruce extract. IMO, this stuff is nasty. If you must use it, a little goes a very long way. If misused, it can give an overpowering, artificial "Pine-Sol" character to your beer.

2) Fermentation temperature. The pitching temperature was way too high, but if you were also fermenting at 70+ F, then your beer is going to be producing all sorts of ugly off flavors.

3) Honey. Some strongly-flavored honeys can impart really unusual aromas and flavors. Something like wildflower honey can sometimes give very musky notes. Again, combined with the spruce and the yeast-derived notes, the effect could be interpreted as "moldy" especially if it's a more "musty," "earthy" or "mushroom-like" moldy character rather than mildew-like.

The bad news is that the spruce and phenolic character is going to take a long time to settle down. Store the beer in a cool place (like that basement of yours) for a few months, then taste it again to see how it's developing. If it's any good, let it sit for another 3 months and taste again, and so on to see if there's improvement.

If the beer is basically good, but just overpowering, consider using it as a blending beer to mix with another batch.

If it sucks, it's sink feed. Suck it up and treat it as a learning experience.   

Offline frochild

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Re: Moldy tasting beer
« Reply #16 on: June 28, 2011, 12:50:37 AM »
Thanks to all above, there is some great information here.  It will be quite the waiting game now.