Savoring Acidity

The Quest to Explain Sourness in Beer.

- Brian Yaeger

Shortly after it opened in 2006, I found myself sitting in the subterranean bunker that is San Francisco’s City Beer Store, sipping on Rodenbach Grand Cru, a beer I hadn’t tried before. Sour fruit aromas and wine like tannic notes greeted my nostrils. “Don’t swallow,” my survival instincts insisted. I ignored them though, and my throat constricted as the sharp, intense Flanders Red made its way toward my stomach. The acetic acid was jolting to my system, yet for some reason I kept drinking.

Despite its bracing flavor, the types of sour-producing bacteria found in highly acidic beers like Rodenbach’s Grand Cru aren’t pathogens. In fact, as an increasing number of consumers have discovered, tart beer is tasty beer. But is there such a thing as too much tartness? How do we determine sourness? And how should brewers relay the quantifiable determination of sourness in beer?

As consumers, we’ve come to rely on several scales and measurements to make judgments about a beer even before we’ve taken a single sip. ABV, or alcohol by volume, reveals the alcohol content so we can anticipate the effect of a beer’s strength. IBU, or International Bitterness Units, tell us what sort of bitter punch a beer is likely to deliver to our taste buds. OG (original gravity) and FG (final gravity) paint a portrait of a given beer’s residual sugars, giving us a sense of how sweet a beer will taste. Even SRM (Standard Reference Method) indicates the darkness and opacity of a beer, alerting us to the flavors the given malts ought to impart. So what’s the best way to communicate a beer’s sourness?