O-2. Some considerations on mash pH prediction

Presenter: A. J. deLange, Mad Fox Brewing Company, Falls Church, VA

Clearly it would be advantageous if brewers could enter parameters describing their malts and water, the amounts of each, and the amounts of any salt, acid, or base additions into a spreadsheet or “app” and have it return a reliable mash pH prediction. This represents the holy grail for home brewers but would clearly be of value to craft and larger commercial brewers as well. In this presentation we offer a proton deficit/ surfeit model in which the predicted pH is the pH at which the total of individual mash component proton deficits equals the total proton surfeit. We explore methods for determining (modeling) the proton surfeit/deficit for each relevant mash component. Among these are a Henderson-Hasselbalch–based model for carbonate and phosphate and, for malts, a simple (three term) Taylor series representation of their titration curves about the distilled water mash pH. Some experimental data are given. While the models for many of the mash components may be sufficiently robust, this is not true for all of them. For example, calcium carbonate and lime additions do not deliver the alkalinity that stoichiometry predicts. A theoretical explanation as to why this may be so is presented. Larger difficulties may lie in obtaining data that accurately reflect the actual acidity or alkalinity of malts encountered in the brewhouse on a particular day. These are discussed, with emphasis on the laborious and time-consuming nature of properly done malt titrations. Variations between lab and brewhouse handling, between malt batches, and the fact that thermodynamic equilibrium is never reached in the mash tun are noted. We conclude that while accurate mash pH prediction may be feasible it may, depending on required accuracy, not be practical.

A. J. deLange is a retired electrical engineer with more than 40 years of experience in signal processing, RF engineering, estimation, and analysis. He is also a home brewer with more than 25 years of experience who has particularly enjoyed applying the disciplines of his professional life to his hobby. He has a keen interest in brewing water chemistry and beer color analysis and has published and lectured on those subjects in the United States and abroad. He is a member of MBAA and ASBC. He has undergraduate and graduate degrees in electrical engineering from Cornell University and was employed by Zeta Associates in Fairfax, VA. He consults for Mad Fox Brewing Company in Falls Church, VA.

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