Author Topic: Low Attenuation in Stout Using WLP005  (Read 607 times)

Offline Carson B

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Low Attenuation in Stout Using WLP005
« on: August 30, 2019, 03:44:05 PM »
First post on here! I'm looking for help/ideas on a considerably low attenuation I just experienced (50%). I'm a relatively new homebrewer who started with IPAs. Just took my first shot at a stout that I was hoping to be around 8.5%, and it came out way lower - around 6%. I'm thinking it has something to do with the grain bill (EDIT: or mash), as I made a 2L yeast starter (I usually make 1L starters for IPAs but figured it wouldn't hurt to up this one to compensate for the additional ABV), oxygenated the wort using pure oxygen (60 seconds through diffusion stone), and fermented at a controlled 68 using SS Brewtech FTSs.

Recipe:

Batch Size: 2.5 gallons

6.41 lbs Maris Otter
0.92 lbs Flaked Oats
0.82 lbs Chocolate Rye Malt
0.62 lbs Chocolate Malt
0.27 lbs Crystal 40
0.11 lbs Roasted Barley

Hops irrelevant.

Yeast: WLP005 British Ale Yeast in 2L starter on stir plate
Mash: Single infusion at 155 for 60 minutes
Boil: 90 minutes
OG: 1.092
FG: 1.044 (way higher than anticipated)

Apart from the FG, I hit all the Beersmith-predicted numbers and even got higher efficiency than I'm used to (usually around 67 and this was 69).

Looking for any ideas or pointers on why this attenuation was so low, if it was the grain bill, something else, or the yeast (though this yeast from what I understand is great for stouts and usually has attenuation in the 67%-74% range.

Thanks so much!
« Last Edit: August 31, 2019, 12:37:55 AM by Carson B »

Offline dmtaylor

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Re: Low Attenuation in Stout Using WLP005
« Reply #1 on: August 30, 2019, 04:10:01 PM »
Welcome to this forum, and to the hobby!

You mashed kind of high at 155 F.  Have you calibrated your mash thermometer in both ice water at 32 F and boiling water (temperature specific to your particular elevation above sea level)?  If it's just a few degrees off and you actually mashed at say 158 F, this could explain the whole thing.

It's not your grist.  Recipe looks good.

WLP005 however is a highly flocculant yeast.  Did you allow enough fermentation time?  It might have helped to swirl the fermenter to keep the yeast into suspension as well.

So, could be a combination of temperature & thermometer calibration, and just the yeast itself.  Those are the main things I see.

Also, double check the calibration of your hydrometer in plain room temperature water.  It might be off by a few points as well -- I know mine is and many are.  Maybe all your hydro readings are too high by several points.  And if you used a refractometer...... I'll fill you in later if that's the case.

EDIT:  IF you were using a refractometer, my standard guidance for that can be found here:

https://www.homebrewersassociation.org/forum/index.php?topic=28544.15
« Last Edit: August 30, 2019, 04:16:27 PM by dmtaylor »
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Offline Carson B

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Re: Low Attenuation in Stout Using WLP005
« Reply #2 on: August 30, 2019, 04:56:32 PM »
Thanks for the response!

Yep, I calibrated everything. I have a big chemistry background from college so I'm pretty anal about those things haha. I mashed at that high of temp for a bit more body and sweetness (I do this will all my NEIPAs - perhaps it doesn't translate as well to stouts), but just not this much... I'll be brewing a similar recipe in the next few days and will shoot lower. Maybe 152 range. Use the same yeast and see what happens.

Fermented for 12 days. Gravity remained the same after day 8.

The high flocculation is something I hadn't thought of, and no I didn't swirl it. I'll give that a go next time.

I use a combo of both hydrometer and refractometer, and before I started brewing I actually happened to read your post that you linked when deciding which to use. I prefer refractometer just because I brew in small batches and those hydrometer pulls really take a toll over time haha. For this batch, both matched for OG, but the hydrometer read 1.048 FG (refractometer after using the Beersmith correction tool was 1.044).

Anyways, thanks for the advice. Definitely going to implement your suggestions for the next round. Cheers!

Offline dmtaylor

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Re: Low Attenuation in Stout Using WLP005
« Reply #3 on: August 30, 2019, 10:01:17 PM »
Well, huh.  Very odd.  I too have a chemistry background, B.S. Chem Eng from Michigan Tech actually.  But anyway.
 Maybe mash pH was much too low from all the dark malts?  These days I'll reserve some or all dark malts for the very end of the mash to keep pH above 5.2, otherwise it could fall into the 4's because dark malts are slightly acidic.  Hmm.... yeah, you have 20% darks and crystal in there, crystal is also acidic.  So with distilled water I'd expect a mash pH of about 5.2, but it could be even a little lower.  I've seen it fall to 4.9-5.0 before.  If that's the case, if you used very soft water, the pH might have gotten too low, preventing proper conversion.  And, IF you added any acid -- I don't think you did, you shouldn't for a dark beer -- this would really take it way down.  Did you measure pH at all?  It's the only other thing I can think of.  You really should aim for about 5.6 for a dark beer.

Hopefully others will chime in too.  I'm usually not the only guy on this forum!  :)
« Last Edit: August 30, 2019, 10:03:17 PM by dmtaylor »
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Offline Carson B

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Re: Low Attenuation in Stout Using WLP005
« Reply #4 on: August 30, 2019, 11:59:08 PM »
pH was 5.21. That's the next front for me - water chemistry. I'd read beforehand stouts were best a bit higher, but I only had acids on hand, so I couldn't raise it. Could be a little bit of everything you've mentioned. Low(ish) pH and on the higher end of temp range. FWIW, Beersmith predicted a FG of 1.037, which was also high. Maybe it's just something about that yeast strain, plus tiny errors here and there with things like pH.

Best part about it, I can try again. I got WLP001 California Ale Yeast this time (instead of trying the same WLP005 like i said in the previous post), and Beersmith seems to think it'll get down to about 1.019. So, if that finishes super high, we'll know it's all on me haha!

Sincerely appreciate your thoughts!

Offline Robert

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Re: Low Attenuation in Stout Using WLP005
« Reply #5 on: August 31, 2019, 12:02:03 AM »
Low wort and beer pH can increase or accelerate flocculation of yeast, potentially leading to underattenuation.  But your pH wasnt all that low, and it's hard to say how much these pH effects manifest in the real world.  Real head scratcher.   Welcome to the obsession, Carson!
« Last Edit: August 31, 2019, 12:04:19 AM by Robert »
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Offline Carson B

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Re: Low Attenuation in Stout Using WLP005
« Reply #6 on: August 31, 2019, 12:22:41 AM »
Sounds like a likely culprit. Best advice/salts/techniques to raise pH?

Thanks Robert! And, yes, the obsession is real. Acute onset

Offline Robert

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Re: Low Attenuation in Stout Using WLP005
« Reply #7 on: August 31, 2019, 12:38:40 AM »
To increase alkalinity, you have two choices, baking soda and calcium hydroxide, aka slaked lime or pickling lime.  If you don't want to add sodium, pickling lime is the choice (usually mine.)  This is slightly complicated by the fact that you are adding calcium,  which drives mash pH down, while adding alkalinity to drive it up, but the net effect is up, and software can handle the the calculations for you.

I suggest going to the Bru'n Water website and reading the Water Knowledge page for a great intro to the subject of water chemistry in brewing.   There's also the Bru'n Water spreadsheet there,  one of several tools available to help plan water treatment for a particular beer.  And their author,  Martin Brungard, is a regular on this forum always willing to help and educate.
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Offline BrewBama

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Re: Low Attenuation in Stout Using WLP005
« Reply #8 on: August 31, 2019, 02:18:24 AM »
Here’s my theory: By using a 60 min mash at the higher temp coupled with this yeast strain, I believe you may have stacked the deck for higher FG.

If I am not mistaken, mashing conditions that favor the action of the enzymes beta amylase and limit dextrinase in the mash create more fermentable worts. I am thinking at the mash temp used, 60 min simply wasn’t long enough to create a wort as fermentable as it would have been if mashed at a lower temp and possibly longer.

Couple the mash condition with this typical English yeast that doesn’t consume maltotriose, attenuates on low the end, and drops out fairly quickly anyway.



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Offline Robert

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Re: Low Attenuation in Stout Using WLP005
« Reply #9 on: August 31, 2019, 02:46:05 AM »
I would bet that BrewBama is definitely on the right  track.  An example of how getting a beer dialed in is a matter of balancing lots of factors that individually aren't decisive, but all add up.  Miss your pH, your mash time/temperature program, your pitch rate, don't account for the yeast's tendencies... no problem on any one.  Get them all just a bit off, and the aggregate effects are noticeable.   And you'll want to learn to consider them as a system:   Think, which factors can I control, and what do I need to do to make up for my limitations?   In this case, if you couldn't better manipulate time, temperature,  and chemistry,  you might choose a different yeast.  If committed to the yeast, you'd probably pay more attention to the mash program.  And so on.
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Offline majorvices

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Re: Low Attenuation in Stout Using WLP005
« Reply #10 on: August 31, 2019, 10:50:54 AM »
How does it taste? If you like the beer you might just package it anyway. Of course if it is going into bottles you have the potential for bottle bombs so that may not be a practical option. You could try pitching another yeast: WY3711 or the dry yeast Belle Saison will ferment out whatever sugars are present over time. It may take a couple of weeks and will most likely be dryer than you intended but it does work. That strain is diastaticus and should be handles with some care but really shouldn't pose any hazard on the homebrew scale.

Offline Carson B

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Re: Low Attenuation in Stout Using WLP005
« Reply #11 on: September 05, 2019, 03:15:41 AM »
Tastes just fine. I bottled three and kegged the rest to compare. I imagine it'll still be good beer, but that low of an attenuation was just odd.

To further the mystery, but perhaps offer an explanation on the low attenuation, after I racked the beer off, the yeast cake was "fluffy" (not compact at all) and just sort of looked dead. I harvested it, washed it, and it continued to have that gray, dead appearance. Pitched it in a fake beer/high starter made with DME with an OG of 1.075, and it sank straight to the bottom. No airlock activity after about 12 hours. Wondering if all the yeast died off early for some reason, though I'm absolutely certain there was no infection or temp swings.
« Last Edit: September 05, 2019, 03:17:18 AM by Carson B »

Offline AzBruin

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Re: Low Attenuation in Stout Using WLP005
« Reply #12 on: September 05, 2019, 05:32:37 AM »
^^Take that same yeast and try it in an SNS starter of lower gravity, around 1.030.