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Well-Known Member
May 30, 2013
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Hello HBT.
Anybody used WLP644 because I'm having very slow activity now compared to very aggressive activity at the start. I did a two stage prop/starter from 1 vial for 60L using 3L of fresh wort @ 23C each time, pouring off approx 80% after chilling each time. I'm estimating yeast count, but should have been plenty and wouldn't mind a technical under pitch.

I'd note that it forms a loose powder sediment, if you can't chill for 2-3 days I'd assume a lot of yeast is still in suspension after 24 and my first discarded spent starter wort went into a separate 5L of fresh wort where it took off like a regular ferm. Through further splitting and prop is now quite a lot of yeast.

First 30 hours were intense with the fermentation looking basically done at 24 hours, 48 down to 7 so I got on with making my additions. Next 24 hours were intense again due to fruit puree though I took no reads. The last four days it has sat pretty much silent except for the occasional airlock bubble, maybe every 15-20 seconds?

So I either ignore the airlock and just consider things done, get to chilling. Leave it until activity ceases completely and then consider it done, get to chilling or I start pulling samples and taking reads until I see a stable gravity. I'm loath to do the smart thing and pull samples because at this point I ferment under pressure, I try and keep things oxygen free from dry hop to package.

I read that WLP644 expresses the STA1 gene so it should be considered diastaticus and capable of drying a beer out completely? Part of me thinks the slow activity could be fermentation, but rate limited due to it being erratic glycolysis due to small amounts of glucoamylase produced by the yeast? Either that or the sign of a slow infection which would be a shame, but further reason to chill now and package so it can be drunk before it gets out of hand.

White labs seem to suggest normal attenuation and with normal pitch rates just get on with it, treat it like a normal yeast. TBH it is going into keg so if it goes in at 6-7 after 2-3 days chilling (reduced yeast count) then I'm not too fussed if it theoretically can ferment dry, I can always vent a keg, plan to store it cold, find high pressures stall out yeast a bit anyway and plan to tap within 2 weeks.

But yeah, incredibly aggressive fermentation first day, up there with some of the most aggressive yeasts I've used. Pathetic ever since. I've roused it twice now as well. Usually when I see this from yeasts while it isn't 'done' (clean up) it is done.


Bringing Sour Back
HBT Supporter
Jan 26, 2017
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I'm loath to do the smart thing and pull samples
Hmm. Give it 3 weeks then :)

WLP644 expresses the STA1 gene so it should be considered diastaticus and capable of drying a beer out completely?
It's not that black and white. Just use the listed attenuation as a benchmark: 85%

Since you're kegging, keeping it cold, and drinking it soon, whatever you do is fine.



Well-Known Member
Aug 6, 2017
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WLP644 is a pretty weird yeast, and it can definitely slow down a lot. Just give it time. It's definitely diastatic but less aggressive than something like a French Saison yeast. Don't worry about it being too "dry" as there's a LOT more to dryness than just a gravity reading.