What is causing this over-attenuation?

[303Dan]

Hey Everyone,

A lot of my beers have been over-attenuating, but particularly the ones I've done with Wyeast 1056. I just did an IPA (grain bill below) that went from 1.066 to 1.007 (88.8% apparent attenuation!). That strain is supposed to be between 73-77%.

Here's the grain bill and my process:

Batch size: 5.5gal
12 lb 2-Row US
1 lb Dark Munich
4 oz Crystal 40
8oz Corn Sugar (end of boil)

90 minute boil
151 degree mash temp
60 minute mash
10 minute mash out at 170 degrees
Made a 2 stage yeast starter (Wyeast 1056) that should have had the pitch rate somewhere around 1.25M/ml/P

It's been in Primary for 12 days, adding dry hop today. Used swamp cooler during primary fermentation. Fermentation temp was around 63-64 degrees F throughout.

OG: 1.066
FG: 1.007
*** Both gravities were measured with wort/beer cooled to about 70 degrees F.

Mash temperature was measured with my Thermapen. I have confidence that it is accurate. Mash lost approximately 0.5 degrees F over the 60 minute mash.

Beersmith had this one finishing at 1.012, so it went quite a bit past that. I don't suspect infection, the sample tastes fine. Just thin and just a touch hot, due to it being about 7.9% ABV I'm guessing.

Any ideas on what could be causing my consistent over-attenuation, or at least what it could have been with this specific beer?

I'm hoping this one turns out okay. Seems too thin for the style, so I'm not sure what I can do to help or fix it.

Thanks,
Dan

 

[flars]

Mashing at a higher temperature, 154° to 156°F, will create more unfermentable sugars, raising the FG. This will also result in a slightly sweeter finished product. Reducing or eliminating the corn sugar will raise the FG slightly and increase the body a bit.

I brew an extract IPA with WY1056, but only get down to 1.008 for FG.

 

[303Dan]

Yeah, I could mash at a higher temp, but the problem I'm trying to solve is that I'm getting inappropriately (or at least unexpected) high apparent attenuation for the given conditions. It seems more like some problem with my process than a direct result of my recipe and mash temp. I shouldn't be that far off of what Beersmith predicts, and definitely shouldn't be getting near 90% attenuation.

Either my mash process is producing a way more fermentable wort than I'm intending, or my fermentation conditions are resulting in higher attenuation.

Am I just over-pitching, maybe? 1.25M is pretty high. If my starter worked as intended, I would have pitched about 600-700 billion cells. I also forgot to mention that I'm oxygenating with pure 02, 45 seconds in this case.

Dan

 

[303Dan]

Oh yeah, forgot to include my water/grist ratio, which is 1.25 qt/lb.

Dan

 

[dmtaylor]

Double check calibration of your thermometer AND your hydrometer. If using a refractometer for FG, don't.

Could also be slight contamination. Use a plastic fermenter? This can harbor wild beasts permanently and needs to be replaced every year or two. Also replace all hoses and rubber gaskets. It may seem unlikely but is very possible.

Corn sugar is only making the problem worse. Replace with 2-row.

It's not from overpitching, mash temp or time or grist ratio.

 

[DurtyChemist]

I think part of it is the extra pound of sugar you're adding. The yeast can eat that quite easy and I don't think Wyeast or White Labs consider adding any extra sugars outside of the mash. I'm assuming you did it to bump the gravity and give it a dry finish but it shouldn't get you an extra 10% attenuation I just think it's a place to start as stated right above this post.

I'd try this exact same batch either at 154F or without the sugar and see what the problem is. Oxygen wouldn't do this on it's own as Brulosophy has plenty of oxygenation experiments including one where he carefully racked the beer into a fermentor and hit 1.024 from 1.090 wort while oxygen dropped him around 1.022 or something close. Yeast pitching isn't even close to the 252 Billion calculated from Brewers Friend needed for 5.5 gallons of 1.066 wort. If you pitched 1.25 Million I'd expect under-attenuation.

 

[303Dan]

Double check calibration of your thermometer AND your hydrometer. If using a refractometer for FG, don't.

Could also be slight contamination. Use a plastic fermenter? This can harbor wild beasts permanently and needs to be replaced every year or two. Also replace all hoses and rubber gaskets. It may seem unlikely but is very possible.

Corn sugar is only making the problem worse. Replace with 2-row.

It's not from overpitching, mash temp or time or grist ratio.

I double-checked my Thermapen with an ice bath and boiling water, looks good.

I used a refractometer for Original gravity, which I calibrated that day. For Final Gravity, I used a hydrometer. I will definitely test that to see if it's out of whack.

I do use a plastic fermenter (Speidel) and I'm actually leaning towards a slight contamination as the culprit. The only thing is, I've had recent beers under-attenuate in that same vessel. If it was harboring some wild stuff, I would expect every fermentation to behave this way.

The only reason I went with the 1/2 lb of sugar was that BeerSmith, with that sugar, had the beer finishing at 1.012. And yes, shooting for drying it out a bit per the style. Is BeerSmith maybe not good at handling pure sugar additions?

 

[303Dan]

I think part of it is the extra pound of sugar you're adding. The yeast can eat that quite easy and I don't think Wyeast or White Labs consider adding any extra sugars outside of the mash. I'm assuming you did it to bump the gravity and give it a dry finish but it shouldn't get you an extra 10% attenuation I just think it's a place to start as stated right above this post.

I'd try this exact same batch either at 154F or without the sugar and see what the problem is. Oxygen wouldn't do this on it's own as Brulosophy has plenty of oxygenation experiments including one where he carefully racked the beer into a fermentor and hit 1.024 from 1.090 wort while oxygen dropped him around 1.022 or something close. Yeast pitching isn't even close to the 252 Billion calculated from Brewers Friend needed for 5.5 gallons of 1.066 wort. If you pitched 1.25 Million I'd expect under-attenuation.

It was actually only 1/2 pound, but I was making the assumption that BeerSmith was correctly handling the sugar addition in relation to gravity and attenuation. Without the sugars, it was finishing higher than that, and I wanted this beer around 1.012.

Pitch rate was 1.25M, but actual number of cells was 695 Billion-ish. Did a two stage starter to bump it up, 1.25 liter first stage and a 3 liter second stage.

 

[303Dan]

I'm really starting to gravitate towards either a faulty hydrometer (I will test thoroughly tonight and post back), or a contamination somewhere in my post boil equipment. I just can't imagine something I'm doing at the mash stage is resulting in this large of an increase in fermentability.

 

[p_p]

I'm really starting to gravitate towards either a faulty hydrometer (I will test thoroughly tonight and post back), or a contamination somewhere in my post boil equipment. I just can't imagine something I'm doing at the mash stage is resulting in this large of an increase in fermentability.

Your hydrometer may be giving you bad readings, worth checking. Thermapens are pretty damn acurate and don't loose calibration.
As far as I know putting more yeast than the optimal rate will not produce lower FG.

Are the attenuation figures declared for the yeast trustworthy? Perhaps when comparing two yeasts against same wort, but not for the same yeast against different worts.

I think you just produced more fermentable wort than the software predicted. Try punching the recipe in brewers friend calculator for the sake of comparing.

Did you mash very long? Did you keep mixing it throughout?
Are you overattenuating on all your recipes?
Have you brew this recipe more than once with different results?

no answer to your question in this post!

 

[motobrewer]

151F mash temp with the majority of grain bill as two-row and some corn sugar is not surprising to me to get you down to 1.007.

 

[m00ps]

Im dissapointed if my IPAs, and even DIPAs, dont get BELOW 1.010

 

[kh54s10]

Also the FG given by Beersmith is a target based on the predicted attenuation expected, recipe and procedure. Small variation in any of these will make a difference.

AND, yeast cannot read the printout from Beersmith and will do what they want to do....

Check the hydrometer. I am not sure that you can really get a "slight" infection but maybe...

If the beer is not to sweet or too dry just take what you get.

 

[motobrewer]

Also the FG given by Beersmith is a target based on the predicted attenuation expected, recipe and procedure. Small variation in any of these will make a difference.

AND, yeast cannot read the printout from Beersmith and will do what they want to do....

Check the hydrometer. I am not sure that you can really get a "slight" infection but maybe...

If the beer is not to sweet or too dry just take what you get.

yeah, beersmith's FG estimations are a WAG at best.

 

[303Dan]

Your hydrometer may be giving you bad readings, worth checking. Thermapens are pretty damn acurate and don't loose calibration.
As far as I know putting more yeast than the optimal rate will not produce lower FG.

Are the attenuation figures declared for the yeast trustworthy? Perhaps when comparing two yeasts against same wort, but not for the same yeast against different worts.

I think you just produced more fermentable wort than the software predicted. Try punching the recipe in brewers friend calculator for the sake of comparing.

Did you mash very long? Did you keep mixing it throughout?
Are you overattenuating on all your recipes?
Have you brew this recipe more than once with different results?

no answer to your question in this post!

Im dissapointed if my IPAs, and even DIPAs, dont get BELOW 1.010

On one hand, I'm trying not to get wrapped around the axle worrying about numbers. The thing that matters most is whether or not the beer is good.

But on the other hand, the more predictable and consistent I can make my process, and the more I understand it, the more likely I'll be able to make the beer I set out to make. And that's obviously my end goal.

So, this beer may very well turn out great. The sample seemed a bit thin, but it's possible that's just confirmation bias after I saw the gravity reading. Plus, it's hard to tell what it'll be like once it's carbed, dry-hopped and cold.

But I would like to be able to better predict the behavior of my fermentations. I did also put this recipe, exactly as it exists in Beersmith, into Brewer's Friend recipe calculator and most of the numbers looked identical. Actually, that calculator showed it finishing at 1.015, so even higher than Beersmith.

Here's a question: is mash efficiency at all directly correlated to fermentability? Because I had much higher than expected mash efficiency than I was expecting, almost 85%. So I diluted the boil volume until I got to my predicted pre-boil gravity, then boiled until I hit my OG (obviously I ended up with a larger than planned batch size this way). Again, all samples were cooled to around 70 degrees F before measuring with a refractometer.

Mash wasn't extra long, 60 minutes. I did NOT mix throughout. Is it possible that I'm getting temperature stratification and there are small pockets that are cooling down and creating more fermentable wort? When I open the mash tun at the end of the mash and measure, I'm within 1 degree of 151. But, admittedly, I did not stir before taking that measurement.

Anyway, like I said, I will test the hydrometer. I'm hoping that's the issue because then everything else would make sense to me.

Thanks to everyone for their thoughts and comments.

Dan

 

[dmtaylor]

Here's a question: is mash efficiency at all directly correlated to fermentability?

No.

Mash wasn't extra long, 60 minutes. I did NOT mix throughout. Is it possible that I'm getting temperature stratification and there are small pockets that are cooling down and creating more fermentable wort?

Possible, but unlikely IMHO.

Anyway, like I said, I will test the hydrometer. I'm hoping that's the issue because then everything else would make sense to me.

Yep, let us know how that turns out. As a point of reference, my hydrometer reads high by 0.003. When I first bought it 15 years ago, it was right on. After dropping it a few times fortunately without breaking it, the paper inside slips and calibration is now off. It's very common and easy to correct once you know the error.

 

[Brew_Meister_General]

A lot of my beers have been over-attenuating, but particularly the ones I've done with Wyeast 1056. I just did an IPA (grain bill below) that went from 1.066 to 1.007 (88.8% apparent attenuation!). That strain is supposed to be between 73-77%.

I had a similar problem which for me was due to prolonged mashing, doing 1 hour at 60c and then 1 hour at 70c, now I'm just going for 1 hour at 70c.

 

[slym2none]

Might it not be a case of yeast doing what yeast do, and it just over-attenuated?

I brewed an extract Irish red, used Notty, and had the recipe in Brewer's Friend tell me I was looking at an approximate FG of 1.013 - it finished at 1.008, with a 1.064 OG reading.

I just figured the yeast did its thing a little too well.

*shrug*

 

[303Dan]

Okay, well I did some experiments with the refractometer and the hydrometer this evening using sucrose/distilled water solutions calculated at different gravities. The refractometer was dead on at all points. Turns out the hydrometer is consistently 2-3 points low in the range of finishing gravities for beer. About 1 point low for pure distiller water, but at 1.010 and again at 1.025, it was 2-3 points low.

So, that actually makes me feel much better. That means this beer is really around 1.009-1.010.

I also went back to my notes for previous beers where I used 1056 and they were all about 4-5 points low compared to the FG predicted by BeerSmith, so apparently that yeast just attenuates stronger with my processes. I edited the yeast ingredient in BeerSmith so I can account for this in future batches.

Thanks everyone for helping me work through this issue.

Dan

 

[p_p]

Okay, well I did some experiments with the refractometer and the hydrometer this evening using sucrose/distilled water solutions calculated at different gravities. The refractometer was dead on at all points. Turns out the hydrometer is consistently 2-3 points low in the range of finishing gravities for beer. About 1 point low for pure distiller water, but at 1.010 and again at 1.025, it was 2-3 points low.

So, that actually makes me feel much better. That means this beer is really around 1.009-1.010.

I also went back to my notes for previous beers where I used 1056 and they were all about 4-5 points low compared to the FG predicted by BeerSmith, so apparently that yeast just attenuates stronger with my processes. I edited the yeast ingredient in BeerSmith so I can account for this in future batches.

Thanks everyone for helping me work through this issue.

Dan

Glad you found your answer. Perhaps not a great deal, but not being able to explain something can drive some men into madness!

One more thing. Mash efficiency as number of points obtained vs. theoretical max. I am always 85%. Overall efficiency is lower due to liquid loses (ie hops absorption, turb and dead spaces).

Now I have found, despite my limited experience, mash temperature and time plays a big role on top of grain bill, of course. Last brew was 90min mash at 64.5 (148) and managed a FG of 1.007. Where other beers mashed for 60 min at 68 (155) have been in the mid high 1.01x albeit some difference in grist composition.

If you really want to go after this one, why not to brew a second time, keep the yeast the same and make other changes (mash temp, grist) then you can punch into beersmith and check if the delta remains always the same.

Good luck

 

[pm5k00]

I am sorry if anyone has already mentioned this, I didn't read every post, but have you checked to make sure your fermenting at the temperature you think you are? If you are fermenting warmer than you thought that could contribute to the attenuation.

 

[Onthebrew]

Can I bump this? I’ve just checked my latest brew and final gravity is 1002. That seems super low. It was 1061. Wyeast 1056. Extra pale malt and 500 g sugar in mash.

1002? Has to be an infection right? Tastes ok at moment though( 18 days in fv)

 

[Dcpcooks]

Need more information to speculate on your batch. The sugar may have something to do with your low FG. An infection won’t get it that low that fast in my opinion.

 

[kh54s10]

Extra pale malt, mashed? What mash temperature? With an extra 1.1 pounds of sugar, why? That would create very fermentable sugars, especially if mash cool. So no, that FG does not surprise me totally.

Check you hydrometer and thermometers to be sure they are accurate.



















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[jtp137]

Im dissapointed if my IPAs, and even DIPAs, dont get BELOW 1.010

I’m with you like them nice and dry

 

[glugglug]

I usually take OG with hydrometer and refractometer. My last brew I took a sample at start of boil with refractometer, and then for og. However at og, sample thingy had water in it, and diluted sample. Noticed when I used hydrometer. If you have both, use them for og.

 

[thehaze]

Im dissapointed if my IPAs, and even DIPAs, dont get BELOW 1.010

Then I would recommend Nottingham, which attenuates for me somewhere between 80 and 85%.