Author Topic: Changing mash profile affects the estimated attenuation.  (Read 2488 times)

Offline Chratz

  • BeerSmith Apprentice Brewer
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Changing mash profile affects the estimated attenuation.
« on: December 31, 2018, 08:03:20 AM »
I'm probably missing something stupidly simple here but I'll throw this one out there anyway:

When changing the mash profile from a standard single infusion profile I normally use, to a step mash profile I created for German Helles it's affecting the estimated attenuation and Final Gravity of my beer thus lowering my estimated ABV. However it does not affect my original gravity at all. The same thing happens when I change between standard light body and full body single infusion profiles.

I guess my question is: How can the mash schedule affect the Final gravity of the beer achieved after fermentation, when it does not affect the Original gravity at all? I thought attenuation was only affected by fermentation temperatures/techniques, yeast type and all that jazz and not the mash.

Huge thank you to anyone who can answer these questions. It's driving me just a little bit nuts right now. I wanna get to brewing! ;)

/Chratz
Skatviken Station Brewery
/Chratz

Offline Oginme

  • BeerSmith Grandmaster Brewer
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  • Goats, guitars, and a home brew; Life is good!
    • Longvu LaManchas
Re: Changing mash profile affects the estimated attenuation.
« Reply #1 on: December 31, 2018, 08:21:18 AM »
It doesn't.  You are experiencing the difficulty in trying to model a dynamic process with a limited number of parameters.

BeerSmith models conversion of the starches based upon the initial temperature within the range of 'optimum mashing' according to the model that Brad has chosen to use.  This means that the window for conversion starts at the full gelatinization temperature of the barley starches (147F/64C) up to the rapid denaturing temperature of the enzymes (162F/72C).  I am guessing that your initial temperature rest near the rapid mash zone is at 145F/63C, which falls outside the ability of the model to predict.  Your next step within the mashing zone described above is where the model will predict the fermentability of the wort.

My recommendation (and what I do) is to ignore the predictions of fermentability since it lies outside the model used.  Yes, you will get a more fermentable wort and you know that the predictions are off but it is easier than trying to fight the limitations of a model which is incapable to managing the effects of various steps within the mashing zone.

Recycle your grains, feed them to a goat!

Offline Chratz

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  • I like exact measurements!
Re: Changing mash profile affects the estimated attenuation.
« Reply #2 on: January 29, 2019, 03:38:49 PM »
Thank you for an elegant answer!
/Chratz

Offline dtapke

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Re: Changing mash profile affects the estimated attenuation.
« Reply #3 on: January 30, 2019, 09:02:16 AM »
Here's a study on mash temps vs. attenuation provided in a back issue of Zymurgy magazine, I'd highly recommend joining the AHA to get this mag for free with membership, Has a lot of great info!
32g eHERMS
Drinking: Dopplebock, NEIPA, Pils
Primary: empty
Secondary/Lagering:
Next Brew: RIS

Offline dtapke

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Re: Changing mash profile affects the estimated attenuation.
« Reply #4 on: January 30, 2019, 09:07:28 AM »
I should note this is a tiny excerpt from the whole of the article which was very interesting to read!
32g eHERMS
Drinking: Dopplebock, NEIPA, Pils
Primary: empty
Secondary/Lagering:
Next Brew: RIS

 

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