Ask The Brewmasters

Hi all, I have a question regarding best practices for when your beer has reached your target terminal gravity but still shows signs of active fermentation. In the past our brewery has soft crashed tanks to 55F in an attempt to slow down fermentation. We use Berkely yeasts Diacetyl reducing yeast so we aren't as concerned about a diacetyl rest. Is it better to let the beer finish fermentation in its own time at fermentation temperature (66-72F) or soft crash to try and keep the beer in spec. Thanks  

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Hudson Fort
Ex Novo Brewing
Corrales NM
(503) 201-5325
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I'd advise against leaving fermentable sugars behind by trying to manipulate your final gravity by stalling fermentation, even if you are using tools to control diacetyl.  You'd likely still have elevated acetaldehyde levels with that strategy and then have risk of any residual yeast slowing fermenting in package causing unwanted results.  I'd suggest making changes in the brewhouse to change your wort composition and trying to blend to spec if you need to.  My two cents is that the brewer should always have the goal of making sure all fermentable sugars are consumed during fermentation.

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Jason Weihbrecht
GM of Brewery Operations
Oskar Blues Brewery
Brevard NC
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Hi Hudson,

Unless conditioning/carbonating the beer in the final package or other similar procedure it is best practice to allow the beer to finish (i.e.-reach final attenuation) before packaging and even then many breweries will fully attenuate the beer before adding a calculated quantity of sugar (and yeast) to achieve a given carbonation level. Fermentable sugar present in the package can provide fuel for un-wanted organisms possibly resulting in production of off-flavors, unwanted secondary fermentation, package over pressurization, etc. Mentioned previously but I recommend reviewing raw ingredients and brewhouse procedures (particularly mashing/mash program). It could be a simple mash time and/or temperature adjustment to achieve the desired FG/ % RDF. Regarding this, a good quality test to implement would be forced fermentations on your filled fermenters. This is a simple test where basically an excess amount of yeast is added to a sample of wort in a beaker/flask which is placed on a shaker table (or something similar). The idea is that the excess yeast and constant agitation attenuates the wort much quicker than the production fermenter so you know where that should finish out (theoretically, at least). Should be able to find SOP on BA website and definitely on ASBC.

Cheers,

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Phil Leinhart
First Key Consulting
Cooperstown NY
(607) 237-4468
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