Improving Yeast Performance for big ABV beers

Yeast selection for high ABV beers

One of the main problems that brewers face when brewing exceptionally big beers is yeast performance. High alcohol big beers are extremely stressful environments for yeast not to mention actually toxic once the alcohol content becomes high enough.

There are yeast strains about that are engineered to deal with these highly stressful environments and have a high alcohol tolerance. But what if you enjoy the character from your own house yeast, it’s a great yeast, it’s served you well but it struggles in bigger beers?

I attended an interesting seminar on this subject not long ago, Kara Taylor from Whitelabs explained that “in 72 hours most flavour compounds are formed, adding yeast later than 72 hours is unlikely to add to the flavour and aroma of that beer”.

A famous San Diego brewery brew a beer with a starting gravity of 1.094, their house strain struggles to finish this beer and stresses out creating off flavours. They start the initial fermentation with their house strain but after 72 hours (approx. 1.030) they repitch with WLP001 to finish the beer. Their house strain provides the malt balance they require while the WLP001 has a better alcohol tolerance and helps to finish the fermentation while alleviating stress.

When adding yeast at this point of the fermentation, there are little to no nutrients left in the beer, there’s no oxygen and there’s alcohol of a percentage that may be toxic to some strains – strain selection is therefore very important.

To test this theory I created an imperial stout wort with a starting gravity of 1.103 I then pitched my favourite dried yeast (usual attenuation of 77% and an alcohol tolerance of 9%) at a pitching rate of 1 million cells per millilitre of wort per degree of Plato.

Realistically I was hoping for it to get to 1.040 and then repitch but it surprised me by stopping at 1030.8. At this point the beer was at 9.7% with little to no nutrients left so I repitched the active dried version of WLP001 an alcohol tolerant strain with its glycogen stores full and nutrient levels high. Within a few hours this had started fermenting again and had dropped to 1.027.

At the end of fermentation the beer ended up at 1.025 and a very healthy 10.4% abv. At bottling time I reseeded the beer with a bottling yeast that performs well at high alcohol percentages just to make sure that there’s enough live yeast cells to carbonate the beer.

The beer itself is beautiful, no off flavours or aromas are evident, there’s no solvent like character or higher alcohols present just a sexy imperial stout that’s an absolute beast. Try it yourself on your next big beer brew and let us know how you get on.

Formerly of Fullers, Thornbridge and Buxton. Now a freelance Black IPA advocate, homebrew geezer and creator of Baby Back Bacon Black IPA™

3 Comments

  • Reply September 12, 2014

    Mark C

    It’s also important to pitch a larger quantity of yeast than normal as there is a lot of work to do. A yeast starter is useful here.
    Aeration is also very important. I usually aerate well before pitching the yeast initially and then again after 12 hours, then watch the fermentation go. It’s amazing. A large headspace in your fermentation vessel is a must.

  • […] Attenuation, alcohol tolerance and pitching rate can cause issues with these types of beers, I used to flog my house yeast to get it to ferment imperial stouts but to be honest it used to struggle. I then learnt about this technique so I use this every time http://www.port66.co.uk/yeast-performance-big-abv-beers/ […]

  • Reply June 21, 2016

    NoIguanaForZ

    …what strains were the initial and bottling yeasts you used?

    And am I correct that by “the dried version of WLP001” you mean US-05?

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