BrewMonitor® offers your brewing team access to insight that has never been available before: high-resolution data from inside your fermentation tank, allowing you to track the progress of your fermentation, analyze results, benchmark future batches, and much more. The resulting graphs for each completed fermentation – dissolved oxygen, pH, gravity, pressure, temperature and conductivity – provide extremely clear views into the events that transpired and techniques that were employed.

This series of articles shows examples of data curves from specific parameters, as they were recorded from the fermentation of various styles in different scenarios. These graphs are from actual fermentations, and offered as a look into how these conditions express themselves as measured data trends. In this installment, we step through some examples of typical pH curves. See our earlier post on typical gravity curves »

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Figure 1: Pale Ale Example. The pH of this pale ale starts just above 5, likely due to manual adjustments of the mash prior to fermentation. The yeast begin to produce organic acids as soon as they are pitched into the beer, and drop the pH even lower. This drop is interrupted by a second knockout, which brings the overall pH of the fermenter up briefly. During peak fermentation, the pH reaches its lowest point as the yeast generate large quantities of pyruvic and succinic acid as part of normal glucose metabolism. As the sugars are consumed, some of these acids are taken up as remaining carbon sources, and the pH level slowly moves up to its end point.
Figure 2: The pH of the lager starts just below 5.5 and moves considerably slower than other beer types owing to the colder fermentation temperature. This slower fermentation means that there is never a significant excess of pyruvic acid in the media because it is being converted to alcohol about as quickly as it is produced. The lager reaches its lowest pH after the period of maximum fermentation, and then rises slightly during conditioning as the last of the acids are taken up by the yeast.
Stout fermentation graphs - pH
Figure 3: The pH of this stout starts quite high, just below 6, and then drops rapidly. The high starting point is likely due to the addition of mineral salts in the brewing process to achieve the flavor and mouthfeel found in stouts. Minerals such as calcium carbonate are often used to balance the acidity of roasted malts by raising the pH. Once the buffering capacity of the carbonate was overcome, the pH followed a consistent pattern of falling to its lowest level during the peak of fermentation, then rising slowly as a portion of the organic acids are consumed by the yeast.
Figure 4: pH Comparison. Despite starting at a much higher pH, the stout finishes at about the same acid level of the pale ale. This is likely due to a larger overall gravity drop and subsequent acid production in the stout. The lager’s slower fermentation rate leads to a much slower production of acid. The softer water profile of the lager provides a lower overall buffering capacity to the other two beers, leading to a lower acid content of the final product.

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eBook: Fermentation Management

Can fermentation management be improved, as a process? This eBook explores, in detail, how fermentation performance data analysis helps elevate product and business outcomes in a modern brewery, whether brewpub, microbrewery or regional craft brewer.

You will learn:

  • Day-by-day performance considerations – learned through the extensive examination of real-time fermentation tank data.
  • Key recommendations from the Precision Fermentation science team at each major step of fermentation – “Day zero” (i.e. before you pitch your yeast), the first 24 hours, and day two through the end of fermentation.
  • Best practices – Activity to watch out for, broken down by each key measurement – Dissolved oxygen, gravity, pH, pressure, internal/external temperature, and conductivity.
  • Key findings that can help you solve problems and improve your results.
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Posted in Brewing Science, pH Monitoring