Difference between revisions of "Beer color to mash pH (v2.0)"

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(How mash pH and beer color use similar formulas)
(How mash pH and beer color use similar formulas)
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* '''pH<sub>grist</sub>:''' is the distilled water mash pH of the resulting grist
 
* '''pH<sub>grist</sub>:''' is the distilled water mash pH of the resulting grist
 
* '''pH<sub>bi</sub>:''' is the distilled water mash pH of the base malt i
 
* '''pH<sub>bi</sub>:''' is the distilled water mash pH of the base malt i
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* '''g<sub>bi</sub>:''' is the base malt i's portion of the grist (g<sub>bi</sub> = 0..1)
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* '''g<sub>sj</sub>:''' is the specialty malt j's portion of the grist
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* '''a<sub>sj</sub>:''' is the specialty malt j's specific acidity in mEq/kg
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* '''B:''' is the buffer capacity of the malt. It is actually the weighted average of the buffer capacities of all the malts present in the grist, but that can be safely neglected here. It has a unit of mEq/(kg*pH)
  
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This formula is a revised version of the formula given in "The effect of brewing water and grist composition on the pH of the mash" <ref name=troester>Kai Troester, [http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdf The effect of brewing water and grist composition on the pH of the mash], 2009</ref>. It simply does the following. The weighted average of the base malt pH and the titration end-point (5.7) of the specialty malts is calculated and used as a starting pH. Then the pH shift that stems from the specialty malts is subtracted. This pH shift is proportional to the total acidity of the specialty malts. The proportionality factor is the buffer capacity B.
  
(1) is a revised version of the formula given in "The effect of brewing water and grist composition on the pH of the mash" <ref name=troester>Kai Troester, [http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdf The effect of brewing water and grist composition on the pH of the mash], 2009</ref>. It simply does the following. The weighted avar
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Most home brewing software calculates SRM as follows
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{| style="width:800px"
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| [[File:SRM_to_mash_pH_formula_2.gif]]
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| (2)
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|}
  
 
=References=
 
=References=

Revision as of 03:41, 10 January 2012

Work in progress.jpg

This article outlines the derivation of two formulas that can be used to predict the grist pH (and with it the mash pH) based on the estimated color of the beer. It utilizes a correlation that exist between the color of a malt and its pH properties. While this correlation is rather loose in some cases it is sufficiently strong for specialty malts to allow the proposal of formulas that can predict the grist and mash pH from the beer's color.

When I talk about grist pH I mean the pH that is inherent to the grist and which can be measured when distilled (mineral free water) is used for mashing.

This article is rather heavy on math and formulas it is provided as a reference for brewers who want to know how mash pH and beer color can be connected on a mathematical level.

How mash pH and beer color use similar formulas

To estimate the grist (or distilled water mash) pH the following formula can be used:

SRM to mash pH formula 1.gif (1)

where

  • pHgrist: is the distilled water mash pH of the resulting grist
  • pHbi: is the distilled water mash pH of the base malt i
  • gbi: is the base malt i's portion of the grist (gbi = 0..1)
  • gsj: is the specialty malt j's portion of the grist
  • asj: is the specialty malt j's specific acidity in mEq/kg
  • B: is the buffer capacity of the malt. It is actually the weighted average of the buffer capacities of all the malts present in the grist, but that can be safely neglected here. It has a unit of mEq/(kg*pH)

This formula is a revised version of the formula given in "The effect of brewing water and grist composition on the pH of the mash" [1]. It simply does the following. The weighted average of the base malt pH and the titration end-point (5.7) of the specialty malts is calculated and used as a starting pH. Then the pH shift that stems from the specialty malts is subtracted. This pH shift is proportional to the total acidity of the specialty malts. The proportionality factor is the buffer capacity B.

Most home brewing software calculates SRM as follows

SRM to mash pH formula 2.gif (2)

References

  1. Kai Troester, The effect of brewing water and grist composition on the pH of the mash, 2009