Off-flavor Follow-up

In my last post on the subject, I mentioned I had just brewed a very light cream ale, a beer in which any of this off-flavor would be immediately noticeable. Sadly, I was right about that! It is quite bad. Like my last post, this is mostly a “brain dump” and thus not quite as coherent as it could be. As always, any help is appreciated.

Given the good quality of the water I brewed this with, I am fairly confident the chlorine or pre-existing chlorophenol hypothesis is out. I do have a few new data points to work with and could instead be looking at oxidation. I had previously discounted it due to the fact the flavor develops almost right away. Generally I’ve seen it stated that it takes a long time for oxidation to show up. But there is a little more this time to suggest it.

At bottling, I noticed none of the specific off-flavor, although there was a bit of acetaldehyde. Out of curiosity I opened the last bottle (only about 3/4ths filled) only two days after bottling. It is already quite carbonated, and it poured with a lot of foam. I immediately got the off-smell and tasted it right away, too. This time I thought maybe I was falsely attributing plastic notes due to reading about such an off-flavor online and my shaky confidence about the water. Although it’s not quite “wet cardboard” or other descriptions of oxidation, there’s perhaps a general staleness to it.

The other half of the 2.5 gallon batch went into a Cubitainer (polypin) with half as much priming sugar. I’ve sampled a few pours despite it being only a little carbonated, and so far there is no real hint of the specific off-flavor or smell there. But there is still that general staleness, I think. So perhaps the carbonation is enhancing my perception of the smell, and perhaps then the smell enhances my perception of the flavor.

That is consistent with past experiences, where I have tasted this during active fermentation or after bottling, but not in the wort or flat beer. Indeed, after taking the bottled beer and pouring it repeatedly between two glasses I started to notice it less and less. So although there’s no reason to think it is a result of overcarbonation or anything like that, it’s probably connected to CO2 as far as my perception is concerned.

There were many opportunities for oxidation in this batch:

  • First, every beer I’ve made from this 10 lb. bag of pale malt has been bad (#3 & #4 from the last post and this one) Although I am crushing it at home and in used it once right when I got home from the LHBS, it’s possible it was old and stale when I bought it. The same goes for the chichas, which were made with pre-crushed malted corn from who knows when, and the first problematic beer which was made with six-month-old precrushed malt. This is supposed to be quite unlikely, but definitely possible. It would be consistent with the smell & flavor being there right from the get-go. However, the malt seems to taste fine raw.
  • Second, in this instance I tried a BIAB, no-sparge mash and let a lot of it drip down from the bag while squeezing it out. Other people have done this many times and report good results, and other beers where I have splashed or dripped a lot (like my popcorn ale and millet saison) had none of this. But hot-side aeration is not impossible, just improbable as far as I can tell so it’s a possibility.
  • Third, and perhaps most damning, I intended to do a short cold crash but ended up effectively doing a month-long lagering since the yeast took forever to drop out. Since it was supposed to be short I replaced the airlock with a piece of foil and a rubber band to avoid suckback. That amount of time with that amount of headspace (half of a 5 gallon Better Bottle) can easily cause oxidation, I think.

Without further experiments I can’t quite discount the possibility that something else is wrong and causing the off-flavor/smell in addition to this beer being oxidized and stale. I can test the malt with side-by-side small mashes with the same water and new malt. I can intentionally splash the heck out of another mash to test that. I am not super keen on wasting a month intentionally oxidizing a beer, but hey, it may be necessary.

This is all quite discouraging, of course, but I intend to figure it out. Thankfully I have had good beers before and in between the bad, so I know it’s not impossible.

7 thoughts on “Off-flavor Follow-up

  1. Bryan (Sui Generis)

    Given what you wrote here – that the flavours appear after bottling – I wouldn’t suspect your bag of grain. I brewed once with some overly-old grain, and you could tell on brew day, an during ferment, something was off (everything smelled stale/musty). At bottling, the staleness was quite pronounced in the flat beer.

    My suspeicion is it may be a bottling issue – how exactly are you bottling (bottling bucket, etc)? The fact this appears only after bottling, and is expressing as a volatile staleness + overcarbonation/gushing, may be a sign of mold or wild yeast contamination. Since this is appearing at bottling time, I would look at cleaning with a harsh cleaner (bleach) all hard components (anything glass/metal) and replacing the soft components (anything plastic) of your bottling system, and thoroughly cleaning all your bottles (2 hour soak in 5% bleach solution).

    Good luck!


    1. DC Yeast Lab Post author

      Thanks, Bryan. My bottling setup is low-tech: I use an auto-siphon out of the fermenter into a stainless stockpot (which I sanitize by thoroughly boiling clean water, and add the priming sugar to that boiled water) and then use the same auto-siphon again out of the stockpot into bottles with a bottling wand. I swirl very gently with the auto-siphon before filling the bottles and let it sit for a little bit to mix.

      I think I’m about due to replace all the plastic parts, so I’ll do that sooner rather than later.

      These bottles were new-to-me bottles from six-packs I bought recently. I rinsed them out after pouring each time (no visible sediment), then soaked an hour or so in PBW earlier on bottling day and then sanitized in Star-San. The acidity of the Star-San has in the past helped rinse out the PBW or Oxy-Clean or whatever hard water residue there was. My first suspicion the first time this happened was Oxy-Clean residue, but that doesn’t seem to be the case.

      But the thing is, while it was definitely true that I only noticed this after bottling for the first beer and this last one, the others I never got to bottling. They all smelled off right after fermentation took off. In one case the whole fridge started to smell like whatever this is during peak fermentation. For that beer, the bit of wort I had left out and sterilized in a flask also developed the smell and flavor, although that was with the same yeast.

      The staleness is present in the flat beer here, but the strong off smell and taste are not.

      1. Bryan (Sui Generis)

        They all smelled off right after fermentation took off. In one case the whole fridge started to smell like whatever this is during peak fermentation
        Ahh, I missed that part. The gushing may still be indicative of contamination in your bottling line (likely your siphon if its occurring with all bottles), but the staleness may very well be due to your grain.

        Grain is cheap – your time isn’t. I’d replace the grain (or at least do a test batch with a single recipes worth of grain ordered fresh from a trusted supplier).

      2. DC Yeast Lab Post author

        FWIW I added a bottling yeast (CBC-1) fresh off of the stir plate. Not sure how much that’d impact the amount of time it took to carb in the bottle. But it may well be infected given how cloudy it is even after a month lagering, plus gelatin in the pseudo-cask version.

        But yeah, I totally agree. I am definitely getting new malt soon. I will have to try a tiny mash side by side with the old stuff (I have very little left anyway) to see what happens.

  2. Bear Flavored

    Forgive me if I’m just spacing out from exhaustion and missed it, but reading through these off-flavor entries, I can’t find any mention of which yeast strain(s) you’re using. Was there anything in common with your yeast selections or were they different for each batch?

    1. DC Yeast Lab Post author

      You are right, I didn’t mention which yeasts I used. They were different strains every batch. From memory: #1 S-04, #2 US-05, #3 WY-1026, #4 a mix of bread yeast & sourdough starter, #5 Cooper’s Ale yeast.

      On some of these I saved some of the wort and pressure-cooked it to ferment separately, sometimes using another yeast. They all ended up with the same flavor, so I never suspected the yeast or infection as the source of the problem.

  3. Pingback: Off-Flavor: Problem Solved, Hopefully | DC Yeast Lab

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