Author Topic: Final Gravity Estimate Calc - Mash profile doesn't change the number...  (Read 9767 times)

Mij

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Hey there,
I was wondering if the calc for the Final Grav Estimate (FGE) was basically the grain bill fermentables * the % attenuation of the yeast?  That seems to be the only way to change the FGE.  I've tried changing the mash temps (160F vs 150F), diff profiles, etc. and don't see any change in the FGE...

Thoughts?
Jim

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #1 on: August 24, 2008, 11:49:42 AM »
Jim,
  No - the mash temperature does not change the FG.  I've been doing some research in this area and have some data I'm hoping to incorporate into a future version.

Cheers,
Brad
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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #2 on: August 24, 2008, 12:57:26 PM »
Jim,

What I do is make up "New" version of the yeast I'm using, name it with the the mash profile I'm using (US05 - 148F mash) and assign the attenuation I get with that that mash profile, with my setup and process on my system. 

What I have found is that every yeast has it's own attenuation curve and the change in attenuation for yeast A for a 1F change in mash temp may be double the change for yeast B.  While there are many, many factors that go into determining attenuation, for any GIVEN setup (that would be yours) by far the two most important variables are yeast choice and mash profile.

Fred

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #3 on: August 25, 2008, 06:37:37 PM »
Quote
No - the mash temperature does not change the FG.

Really?
I don't use the software (though I'd love to see the source code, what is it written in?) but I've found from personal experience and research that the mash temp does have an effect on the ratio of fermentable sugars to non-fermentable dextrins, and thus the final gravity of the brew.

No offense dude, but to say that the mash temp doesn't affect the final gravity is false.
"To alcohol! The cause of - and solution to - all of life's problems!" -Homer Simpson

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #4 on: August 25, 2008, 06:44:58 PM »
I don't know the rate of alpha-amylase vs beta-amylase in their chopping of starches into dextrins and sugars with regards to temperature, but I'm sure that it would be a matter of research to find the rates based upon viscosity and temperature for each enzyme and incorporate that into your software.

But to tell someone that mash temp has no effect on final gravity is a falsehood.
"To alcohol! The cause of - and solution to - all of life's problems!" -Homer Simpson

Offline bonjour

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #5 on: August 25, 2008, 06:49:04 PM »
Quote
No - the mash temperature does not change the FG.

Really?
I don't use the software (though I'd love to see the source code, what is it written in?) but I've found from personal experience and research that the mash temp does have an effect on the ratio of fermentable sugars to non-fermentable dextrins, and thus the final gravity of the brew.

No offense dude, but to say that the mash temp doesn't affect the final gravity is false.
A misunderstanding,  In the BeerSmith program, mash temp does not have any impact on FG.

In real life you are correct, no doubt.

Fred

Mij

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #6 on: August 26, 2008, 01:13:54 PM »
Sorry guys!  Upon reading my post again, I guess I can see how it would look like there might be no correlation between Mash Temp and fermentability.  On the positive side, the answer given to my initial post was what I was looking for - does Beersmith process the calc in the "proper" manner (adjust the FGE up or down based upon the mash temp/time/etc)

By the way, I thought the idea of using custom yeast profiles was great!  Thanks alot!

Jim

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #7 on: August 26, 2008, 06:25:04 PM »
I apologize, I misunderstood.
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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #8 on: August 26, 2008, 06:32:33 PM »
No problem.

I do more predicting FG than any other brewer I know.  I have found only a limited amount of literature on the subject.  If you could steer me toward some more I would greatly appreciate it.

Fred

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Re: Final Gravity Estimate Calc - Mash profile doesn't change the number...
« Reply #9 on: August 26, 2008, 06:48:04 PM »
I've usually reference the Papazian books, the Guide and Companion.
All other research has told me the same thing.
The lower the mash temp the lower the FG, but it takes longer. 
I've waited 2+ hrs for a 140-145 degree mash to pass an iodine test.
The higher the mash temp the higher the FG, and I've completed 155 degree mashes in 45 minutes.

And the difference between the two can be a FG of 1.004 for a low temp mash to 1.12 for the exact same ingredients mashed at a higher temperature.

I haven't done the research into finding equations and curves for predictable results, but I'm sure they exist.
"To alcohol! The cause of - and solution to - all of life's problems!" -Homer Simpson

 

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