Difference between revisions of "Beer color to mash pH (v2.0)"
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Using (4) and (5) to express a<sub>sj</sub> and g<sub>sj</sub> in (1) gives: | Using (4) and (5) to express a<sub>sj</sub> and g<sub>sj</sub> in (1) gives: | ||
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+ | | [[File:SRM_to_mash_pH_formula_6.gif]] | ||
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+ | To continue working with (6) and | ||
=References= | =References= |
Revision as of 01:24, 11 January 2012
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 formulasTo estimate the grist (or distilled water mash) pH the following formula can be used:
where
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
where MCU means Malt Color Units. It is the MCU formula that shows striking similarity to the pH formula (1)
where
The goal is to express the SUM(asj * gsj)/B term from (1) with the SUM(csj * msj) / Vw term from (3). This is simple for the crystal and lightly roasted specialty malts where the following relationship between color and acidity has been found [1]:
In addition to that gsj needs to be expressed as msj
Where mg is the weight of the grist in pound. Using (4) and (5) to express asj and gsj in (1) gives:
To continue working with (6) and References
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