Author Topic: Beer smith 3 over predict attenuation  (Read 246 times)

Offline lemmeholdthat

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Beer smith 3 over predict attenuation
« on: September 04, 2019, 07:31:38 AM »
I have noticed that beersmith 3 over predicts the attenuation of beer independent of what the upper and lower bounds of the yeast attenuation limits are.  The only way to change the expected FG is to lower the yeast alcohol tolerance.  Any ideas here?

Offline Oginme

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Re: Beer smith 3 over predict attenuation
« Reply #1 on: September 04, 2019, 08:40:45 AM »
The fermentability range of a yeast is given by the supplier based upon the results from fermenting a standard laboratory wort which has a given fermentability.  When you change the amount of fermentable sugars (such as with changing the mash temperature or introduction of multiple saccharification rests) of a wort from this 'laboratory wort', it will produce a greater or lesser the amount of sugars available for the yeast to consume.  In your case, having three rests within the alpha and beta amylase activity range should produce a maximum fermentability of the wort, and the program does reflect that by setting the attenuation potential of the wort higher and predicting a lower FG.  If you were not targeting a high degree of attenuation from the wort, why would you choose this mashing profile?

Having said that, the prediction of FG is subject to a number of influences from the process (mashing time/temperature, yeast health, fermentation profile) which cannot be well modeled.  The model for adjustment of the wort fermentability used in BeerSmith, which can be seen under 'options' > 'advanced', is pretty standard.
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Offline dtapke

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Re: Beer smith 3 over predict attenuation
« Reply #2 on: September 04, 2019, 08:46:08 AM »
well for what its worth that yeasts average apparent attenuation is 82% per their website, which means that the reduction to 72-77%(avg 75) is wrong.

your mash profile clearly was designed to hit maximum fermentabillity. (and really the steps after 147F are kinda pointless... but hey! you do you...)

I can assure you, if you brew this recipe, you will almost certainly hit 1.009
32g eHERMS
Drinking: Dopplebock, NEIPA, Pils
Primary: empty
Secondary/Lagering:
Next Brew: RIS

Offline lemmeholdthat

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Re: Beer smith 3 over predict attenuation
« Reply #3 on: September 09, 2019, 09:00:48 AM »
I have found that this Chevallier malt is only roughly 75% fermentable so trying different mash strategies to make the wort more fermentable.  Right now it looks like this beer is going to be sitting at FG of 1.020.  I've hacked beersmith to work with this particular lot by just cutting this malt into two portions, and indicating one is unfermentable and the results jive with the last 6-7 brews with it.  Once this is done beersmith reliable predicts the FG again.
« Last Edit: September 09, 2019, 09:08:23 AM by lemmeholdthat »

Offline dtapke

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Re: Beer smith 3 over predict attenuation
« Reply #4 on: September 10, 2019, 08:20:38 AM »
Hmmm. I thought I replied to this again, the attenuation does in fact work, I dropped attenuation down to 65% and it reacted appropriately.

perhaps you need to alter the profile of the malt if that's where the issue resides. BSG lists it as 79%
32g eHERMS
Drinking: Dopplebock, NEIPA, Pils
Primary: empty
Secondary/Lagering:
Next Brew: RIS

Offline Oginme

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Re: Beer smith 3 over predict attenuation
« Reply #5 on: September 10, 2019, 09:49:04 AM »
I have found that this Chevallier malt is only roughly 75% fermentable so trying different mash strategies to make the wort more fermentable.  Right now it looks like this beer is going to be sitting at FG of 1.020.  I've hacked beersmith to work with this particular lot by just cutting this malt into two portions, and indicating one is unfermentable and the results jive with the last 6-7 brews with it.  Once this is done beersmith reliable predicts the FG again.

So putting the prediction of FG aside, what did you actually achieve for FG?

Recycle your grains, feed them to a goat!

Offline lemmeholdthat

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Re: Beer smith 3 over predict attenuation
« Reply #6 on: September 11, 2019, 12:42:39 PM »
Hmmm. I thought I replied to this again, the attenuation does in fact work, I dropped attenuation down to 65% and it reacted appropriately.

perhaps you need to alter the profile of the malt if that's where the issue resides. BSG lists it as 79%

I have the malt yield at 79.6% based on the lot analysis, which I have conveniently lost.  I was able to adjust the max attenuation of the yeast way down, but think the problem lies in the malt not being 100% fermentable.

So putting the prediction of FG aside, what did you actually achieve for FG?

1.022

Offline Oginme

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Re: Beer smith 3 over predict attenuation
« Reply #7 on: September 11, 2019, 12:49:50 PM »


1.022

Is that measured with a hydrometer or a refractometer?  If with a refractometer, are you entering in the sg directly or using the program to convert from a Brix reading?


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Offline lemmeholdthat

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Re: Beer smith 3 over predict attenuation
« Reply #8 on: September 11, 2019, 02:15:19 PM »


Is that measured with a hydrometer or a refractometer?  If with a refractometer, are you entering in the sg directly or using the program to convert from a Brix reading?
[/quote]

Measured with both.

Offline Oginme

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Re: Beer smith 3 over predict attenuation
« Reply #9 on: September 11, 2019, 05:36:37 PM »
So with a starting gravity of 1.060 and finishing at 1.022, your attenuation is at 63% which is well below the range for the yeast.  This suggests that your fermentation stalled or was stopped prematurely.  I have never had much of an issue with the FG predictions of BeerSmith.  I've always been within a couple of points of the predicted value.  I would recommend taking out about 300 ml of the wort and adding more yeast to force ferment it and see if it will attenuate further.  This will tell you if it is a stalling of the fermentation or if your wort was just not fully converted.
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Offline dtapke

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Re: Beer smith 3 over predict attenuation
« Reply #10 on: September 12, 2019, 07:18:57 AM »
So with a starting gravity of 1.060 and finishing at 1.022, your attenuation is at 63% which is well below the range for the yeast.  This suggests that your fermentation stalled or was stopped prematurely.  I have never had much of an issue with the FG predictions of BeerSmith.  I've always been within a couple of points of the predicted value.  I would recommend taking out about 300 ml of the wort and adding more yeast to force ferment it and see if it will attenuate further.  This will tell you if it is a stalling of the fermentation or if your wort was just not fully converted.

I can't agree with this more... doesn't seem to be a program modeling issues, seems to be an issue in the brewhouse at some stage. A forced fermentation test as above will help show where the issue came from. make sure you've calibrated all of your thermometers for your mashing process.

Malthouses don't lie on their analysis... otherwise they'd be out of business in a hurry. if the malthouse gives 79%, the malt is 79%. Breweries going through skids of malt would flip out if they found a malt consistently underperforming... that's dollars out the door. lots of them.
32g eHERMS
Drinking: Dopplebock, NEIPA, Pils
Primary: empty
Secondary/Lagering:
Next Brew: RIS

 

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