understanding PH and titratable acidity in sour beer:

tools For Brewers and enthusiasts alike

ph (a measure ment of the power of an acid in solution) has often been used by brewers to describe the sourness of their beer, but recent research has shown not only that titratable acidity (a measurement of volume of acid in solution) correlates more closely to perceived sourness, but that additional factors—residual sugar, type of acids present—are equally important. Stan Hieronymus looks at the latest data and market trends.

CONSIDER THE WORDS USED to describe the character acidity may add to a particular wine. One with pronounced acidity is described as bright. One with acidity but little substance is thin, and one with very high acidity and little fruit flavor is austere. A soft wine has low acidity, a flabby one even less.

Sometimes the same descriptors are appropriate to use with beer, particularly those flavored with fruit and ones categorized as sour or wild. They are only a starting place, just as are the measurements brewers take to indicate the level of acidity in a particular beer. Here’s how Ehren Schmidt at Toolbox Brewing in north San Diego County characterizes two of them: potential of hydrogen (ph) and tritratable acidity (TA): “ph is the first look, peeking in the window. TA is really putting it under a microscope.”

ph measurements, of course, are used in scores of industries and throughout the brewing process, for both sour and “clean” beers. In a sentence, it is expressed on a logarithmic scale (so that a change of one ph unit corresponds to a tenfold change in concentration) with numbers below 7 more acidic than pure water, those above more alkaline. ph measures only disassociated hydrogen, but the organic acids in fermentation are weak acids and do not disassociate as easily as strong acids. TA measures both associated and disassociated hydrogen. It is not the same at total acidity (although both are referred to as TA), which is harder to measure, but it is a good approximation in both beer and wine.

For a primer on titratable acidity see “Quantify Your Funk: A Primer on ph and Titratable Acidity” (October/november 2015), but one important variable is

the acid that is used in the calculation because TA basically measures the ability of an acid in beer or wine to neutralize an alkaline substance. Units of TA are quoted in grams per liter, and TA is expressed in terms of those different acids. In wine that’s usually tartaric acid and in beer lactic acid, although other acids can be specified. Unlike with ph, which is logarithmic, the relationship between TA and perception tends to be linear so that when TA doubles, drinkers perceive the beer or wine as twice as sour.

ph and TA are, first of all, tools that Schmidt uses in the brewhouse, but in the case of TA, it may also give drinkers a better idea of what to expect when they order a Toolbox beer. Again, the numbers are simply the beginning of a conversation because there’s more to these beers than acidity. “People get caught up in the idea that [more] sour is better,” Schmidt says. That is as frustrating for him as it is for other brewers. “I spend endless hours finding microbes that provide additional flavors. There’s a lot more than the sour aspect.”

“People get caught up in the idea that [more] sour is better,” Schmidt says. That is as frustrating for him as it is for other brewers. “I spend endless hours finding microbes that provide additional flavors. There’s a lot more than the sour aspect.”

A Sensory Challenge

It seems a bit like twenty years ago, when many brewers and drinkers rated IPAS based on IBUS, and more equaled better. Intuitively everybody agrees that is not