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Brew-In-Review: Stalled Fermentation

Posted by Rob Hern on

Recently I ran into an issue that I have not had to deal with in the past: a stalled out fermentation. I have had quite a few homebrewers come by the shop asking why they are stuck in the mid 20’s with their wort - beer limbo liquid. Let’s get into it. When it comes to stalled fermentations there are a few easy places to start:

  • Yeast health - old yeast, poorly stored. If you did a starter, it will probably be pretty obvious if the yeast isn’t super healthy. If you didn’t, you should.
  • Yeast Starter - Did you do a starter? Sure, you can generally get away without doing one, but why risk it? You know what day you are going to brew, so make the starter happen 48 hours prior. Make sure that you have sufficient yeast available for the amount of wort and original gravity.
  • Wort Oxygen - yeast needs oxygen to kick in fermentation. There are certain brews that I do not oxygenate (most of my quick turn around sours with lactobacillus), but it’s a good general principle.
  • Fermentation Temperature - are you controlling the temp? Do you know the temp?

What Happened with my Beer?

GoseI brewed a Gose using Escarpment Lactobacillus blend and their Ontario Farmhouse - big lacto starter and what I thought was a sufficiently built up ON Farmhouse - and then I open fermented, which usually leads to a pretty rocking fermentation. My OG was 1.044 (pretty small beer). I pitched at a toasty 29C. The next day fermenter was sitting at 28C and, because it was open ferment, I was able to peek my head in and see a nice layer of krausen building on top. Went away for Thanksgiving thinking all was right in the world and came back to a fermenter at 26C, a pH of 3.3 and a gravity of 1.027. What the fork? Krausen had completely dropped out.

I was annoyed and so immediately blamed my yeast supplier for selling me faulty yeast … Ha! Kidding. No one would do that...… right? After talking to Escarpment, Richard informed me that due to the intense pH levels of my brew, I probably should have built up my starter even larger. Keep this in mind if you are playing around with sour beers with low pH. Err on the side of huge when it comes to yeast pitches.

How Did I Get it Down?

The first thing I did was get the heat on and make sure that fermentation would not continue to drift lower than 25C. If you stall out, get your beer back into the ideal temperature range for the yeast you are using.

Next thing I did, which was not pretty, was dump in a ton transferring to the barrelof BE-134 saison yeast to get my yeast count up high. Super frustrating because no one likes buying and using extra yeast. Once this was done I continued with my note taking, checking in on things every morning and sometimes in the evenings as well. I checked temperature, pH and gravity and inspected the wort for signs of krausen reforming.

In the end, krausen did reform and from Tuesday afternoon to Thursday, the beer was slowly saved. I am bummed because this was my first go with the Escarpment ON Farmhouse and now the beer is a real bastard. At the end of the day, though it’s all good because the final gravity is sitting at 1.013. Not as low and dry as I usually like my farmhouse, but I will take that over 1.027 any day.

Any success or horror stories about your own stalled fermentation experiences? Feel free to share 'em in the comments.
Life is Short. Homebrew.
- Rob.


1 comment

  • Hi Rob,

    I’ve had a few instances of stuck fermentations over the past few years. I’ve solved them in much the same manner as you describe, except that rather than buy new yeast, I’ve used yeast from my following batch of beer.

    In practice, it’s worked like this. Brew the beer. Monitor the fermentation. Eventually notice that it won’t drop below 1.017 or whatever. Move it somewhere warmer. Cross my fingers. Become frustrated. By then, I’ve probably put on a new brew which has completed secondary fermentation, so rack, then swirl and dump the remaining yeast from the second batch into the first batch. Generally, that has been successful in getting the fermentation to complete.

    What I’m curious to know is whether an insufficiently low pH might be a factor in stuck fermentations. I’ve been doing a rye beer (about 4% rye malt) for 5 years running now and it has finished at between 1.015 and 1.020 for the last three years. I haven’t consistently measured or manipulated pH until about two years ago, but this year I noted the mash pH was about 5.95, and the beer, when I last checked, was stalling at 1.017.

    Do you think the wort pH could have something to do with that?

    Gord Maxwell on

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