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I'm brewing with Wyeast's West Yorkshire Ale yeast, which has a documented alcohol tolerance of 9%.

I'd like to push that boundary by brewing an 8.5% ale and wonder what to expect. Common sense says that this constitutes stressing the yeast, so one would expect the normal things that go along with that, like under-attenuation, stuck fermentations, increased esters.

For the sake of argument, let's just assume that the beer will be well-pitched and well-aerated, to give the brave boys the best chance.

Does anyone have personal experience with pushing yeast to their limit?

UPDATE

The beer I ended up making was not near the alcohol tolerance, nor could it have been, but I still ended up learning something.

The beer (1.064) fermented out to 1.020 with West Yorkshire yeast (6% ABV) and 1.013 with Nottingham Dry yeast (7% ABV). The Nottingham is much better-tasting and clearer to boot. I still love the Timothy Taylor yeast for its flavors, but it would seem that sticking to lower gravity beers is best with this yeast.

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3 Answers 3

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If you aerate well and pitch a large starter, you can go beyond the listed alcohol tolerance. The same goes for going below the listed minimum temperature on ale yeasts.

You should also try to control fermentation temperature to ensure it doesn't drop during fermentation. If you don't have good temperature control, start the temperature low and it will rise.

If you start the temperature high it could rise above desirable temperature levels AND drop in temperature as fermentation slows if it's above ambient temperature, the latter of which will likely result in incomplete fermentation and both could result in off-flavors.

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I've not done this with beer, but it's fairly common when producing mead to choose a yeast with an ABV tolerance under what you would get if all the sugars fermented out - the excess sugar remains unfermented leaving some sweetness behind.

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  • And do you find that the alcohol tolerance numbers given by the yeast labs are fairly accurate?
    – Rich Armstrong
    Feb 7, 2012 at 14:12
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    I think if anything they were too low. The high-alcohol mead yeast was rated at 18% abv, but there wasn't much residual sweetness left. (I'll have to open a bottle - it's been 2.5 years now, so will be interesting to see how it's mellowed.) But of course, this is just one instance, and with different yeast, so ymmv. If possible, add the fermentables in stages to get the best attenuation.
    – mdma
    Feb 7, 2012 at 14:20
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The alcohol tolerance figures are very approximate and depend on yeast health, pitching rate, etc. In general, a beer yeast will easily ferment 10% ABV, regardless of the listed tolerance.

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