What attenuation percentages have people actually seen with this yeast?

The back of the package specifies the attenuation as "HIGH", but my own experience suggest that it is medium or low.

  • Apparently this yeast has been replaced by: "M36 Liberty Bell Ale Yeast".
    – Jeff Roe
    Commented Oct 8, 2016 at 17:37

3 Answers 3


The attenuation rating for yeast is meant as a way of comparing one strain to another using a standard wort. It may not reflect the attenuation you can actually expect. The actual attenuation is much more dependent on wort composition than attenuation rating. Using the same yeast I can get anywhere from about 60-85% attenuation depending on the wort.


I made the following beer:

90% malted 2-row barley
10% flaked maize

mashed between 66 and 69 degrees celcius

1.043 original gravity
      fermented with M79
1.011 final gravity

Had I fermented this with my usual Nottingham, I would have expected this to get down to around 1.007 FG. I fermented with M79, and it only got down to about 1.011 (about 70% attenuation).

(The beer has been in the bottle only for one week, but so far it's tasting very nice.)

Here is some support for my belief that Nottingham would have attenuated this quite a bit further. I brew with what I call a "parallel parti-gyle" system which allows me to make 2 beers (with potentially different gravities) from the same wort. The other beer I made with this wort yielded:

1.052 original gravity
      fermented with Nottingham
1.008 final gravity
  • At 66°c 150°f you didn't get any beta-amylase action, and made it less fermentable. Commented Jul 2, 2016 at 19:20
  • @EvilZymurgist: Sure, but I've done mashes like this many many times, and I fully expect that Nottingham would have gotten this beer down to 1.007.
    – Jeff Roe
    Commented Jul 2, 2016 at 19:50
  • 2
    You will indeed get some beta action at 150. howtobrew.com/assets/img/assets/f79.gif
    – Denny Conn
    Commented Jul 4, 2016 at 15:23

It could be that your pack wasn't as healthy or fresh as what you are used to seeing with Nottingham packs. I saw several other posts online of poor fermentation characters from this same yeast.

So comparing the attenuation from one manufacturer to the next might be a little misleading. I'd had to see how low attenuating mangrove jack yeast strain would perform based on this data.

If you were doing true partigyle it is possible that the second runnings started to pull a little more non fermentables from the mash too. But your method of PG might be different from mine, so YMMV.

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