Perceived Sourness, pH, and Titratable Acidity in Sour Beers

By: TJ Grisel, Beyers Analytical Brewing Sciences, LLC

he rise of sour beers in the craft beer industry has necessitated a standard method to analytically measure the sourness of a given beer. Brewers use pH as a measure of acidity in beers however pH does not reflect the perceived sourness of a beer. Lack of an accurate measure for sour taste can hinder brewers’ ability to establish quality standards for both sour and non-sour beers.
 
If not pH then what can you do to test this sourness? Developments in the production of sour beers indicate that titratable acidity (TA) is one of the best methods to measure the sour taste. TA is defined as the sum of titratable acids by neutralizing the acids with a base. Think back to chemistry class in high school when you would drop something like sodium hydroxide into a solution to get a color change. This is the process that one takes to get these TA values.
 
A study was done to test the perceived sourness and TA values. Beyers Analytical Brewing Sciences, Fermentation Science and Technology program at Colorado State University and Gilded Goat Brewing Company in Fort Collins, CO completed the study. A sensory evaluation was conducted to test the sourness by using a pH meter, TA methods via the American Society of Brewing Chemists (ASBC) and a RedCheck Titratable Acidity kit. The study concluded that a higher TA values were more indicative of higher levels or perceived sourness by the sensory panel. An interesting note is that when they looked at the time it took to take the measurements it was noticed that the RedCheck kit took considerably less time than the other methods of testing TA.
 
The understanding of TA and thus organic acid content is best utilized by the brewer because it bridges the gap between analytical data and sensory perception. This provides an additional control point for the monitoring of out of specification beer.
 
While TA is not a new concept, as it is used within the winemaking industry, it certainly is newer within the beer industry. Those brewing sour beers more frequently are now adding a TA value on the bottles similar to an IBU value. One example where you would see an organization implementing this is, Firestone Walker. The beer Lil Opal was one of the first to display it. As a maker of some great lambics, it seems they see it as a value added to help people understand the different levels of these type of beers. Learning what TA is and understanding this parameter can add consistency when dealing with acids, lactic acid. You must continue to measure pH as it is one of the most basic measurements you can take, and implementing TA through either colorimetric or potentiometric methods will help you dial in the perceived taste of your product.

Whether it is for your own or friend’s consumption or you are starting a commercial brewery, people want to know they can expect a certain flavor from your beers. Don’t fail in this expectation and get the tools you wish use to start measuring titratable acidity.
 
Have additional questions about how the in-house titratable acidity kit works, please contact us!