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Old 10-14-2010, 05:03 PM   #1
warnk
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Default WLP001 94% attenuation?

1 batch ago, I did an IPA using WLP001. I re-pitched what I could siphon out of the carboy into a 2qt starter. The starter was sluggish, but was at high krausen when I pitched it into my last batch, an american brown, 3 days later.

This was an all grain batch, 1lb (10% of grain bill) was dark brown sugar. I just changed my mashing setup, and I'm not used to it yet, and accidentally held too long at 148-ish. So, I'd expect the result to be maybe on the drier side, and pretty thin.

I just kegged the brown last night. I took a swig of my sample and my, did have a burn to it. I poured it into thief and took a reading -- no wonder: 1.003

OG of the batch was 1.064, down to 1.003: 94.5% apparent attenuation. What in the wide, wide world of sports is going on here? Rhetorical question I suppose. Obviously some super-yeast made it's way into my starter, I doubt a poor mash could cause this.

Anyone ever run into this?

tl;dr - My yeast has grown too strong. Mutiny inevitable. Please send help.

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Old 10-14-2010, 05:08 PM   #2
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You mash at a really low temperature and used a fair amount of sugar. I'm not surprised you had the beer dry out the much.

How long did you mash?

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Old 10-14-2010, 07:14 PM   #3
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No doubt the beer should have finished out drier, after that mash. I did expect that, but 95% attenuation is way beyond even my highest guess.

I hit 148F with infusion, but had to decoct due to the volume of mash. Mash probably did sit at 148F and dropping for 45m, maybe longer but probably long enough for a full conversion either way. I brought the mash to 156F after decoct. Substituting 1lb sugar for similar amount of extract in grain should only drop terminal gravity 1-2GU in 5gal batch, comparatively.

Of course, my opinion is skewed, this has never happened to me before. I'm surprised by the attenuation -- my beers always finish on the low end of attenuation. WLP001 always finishes at 73-75%. 80% would be optimistic. 90% would be a fluke. 95% and something has to be up.

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Old 10-14-2010, 07:18 PM   #4
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infection could push it lower.

or an inaccurate OG reading.

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Old 10-14-2010, 07:25 PM   #5
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You mayhave selected mostly yeast that dropped out last. This, with the mash temp, could attenuate too much. I would not repitch that yeast anymore.

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Old 10-14-2010, 08:07 PM   #6
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Quote:
Originally Posted by jmo88 View Post
You mayhave selected mostly yeast that dropped out last. This, with the mash temp, could attenuate too much. I would not repitch that yeast anymore.
I did suspect yeast selection could be one of the causes, the yeast seemed slow in the starter and the carboy. I don't normally repitch, repitching into the starter was a last minute decision. I'd assume infection of another yeast strain the next likely culprit.

I thought OG might be wrong too, but my math from preboil gravity and volume work out to the same.

Seems like a perfect storm of sorts. I'll leave the brown sugar in next time I do this recipe, but I'll make sure I hit the right mash temp.

The yeast has already be reassigned to cleaning out my shower drain.
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Old 10-15-2010, 02:35 AM   #7
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I washed a batch of wy1968 recently and due to my laziness I did a pretty terrible job. Anyways, just used that yeast in an ESB and it took it from 1.058 to 1.004! That's gotta be a record for that yeast.

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Old 10-15-2010, 01:59 PM   #8
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Yeah, don't recall if it was 1056 or WLP001. Either way I had a APA come out around a 1.004 I think from 1.060ish.

I added 1/2# malto dextrine at bottling (maybe secondary) and it came out fine. I think each 1/2# will raise a 5-gallon batch .002 if memory serves me correct. So if you want a 1.010 body then add 2 lbs.

Next time mash higher.

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