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Savoring Acidity: The Quest to Explain Sourness in Beer

Feature by | Nov 2016 | Issue #118
Photo by Jacqueline Pilar

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 winelike 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?

At Firestone Walker’s Barrelworks, masterblender Jim Crooks and director Jeffers Richardson have an answer. And it’s not pH, which represents the alkalinity or acidity of a solution on a scale from 0–14. They don’t believe pH matters, and prefer to use TA: Titratable Acidity. As Crooks explains, pH only measures free hydrogen ions while Titratable Acidty “helps you see all the hydrogen ions involved. It’s a measurement of the total amount of hydrogen ions [or acidic compounds] tied up in other bonds.” In the case of beer, we’re generally talking about weaker acids like lactic and acetic.

A quick chemistry lesson: Scientists titrate a solution to figure out the concentrations of different compounds in that solution. Titration makes a concentration known through the measurement of the total hydrogen ion concentration floating freely in solution and those ions still tied up in bonds. By titrating a sour beer, a brewer (or a lab tech) can determine the amount of acid in the solution.

Titratable Acidity isn’t new; winemakers have used the measurement for decades. And while virtually every brewer involved in the production of sour beers—from kettle-sours to barrel aged wild ales—can tell you what a beer’s final pH is, they’re loathe to announce it to the public either because the average consumer doesn’t understand it, doesn’t care about it, or, in some instances, a brewer simply doesn’t want it known. Likewise, brewers are increasingly thinking about TA, but as of now, California’s Firestone Walker is nearly alone in its willingness to print the measurement right on the labels of the sour beers coming out of its Barrelworks operation in Buellton.

Richardson, in an effort to make his case for Titratable Acidity, has recently been traversing the country conducting ticketed seminars called “Jeffers Drops Acid (Knowledge).” Turning up in beer bars like Saraveza in Portland, Ore., and tasting rooms like the Side Project Cellar in St. Louis, he guides attendees through a lecture and beer tasting that aims to unpack the relationship between acidity and sensory perception.

“Using pH does not correlate directly to what we are tasting,” explains Richardson. “For example, a lactic acid and acetic acid of pH 3.5 will taste very different. One will taste more sour than the other. That’s where TA steps in to measure acid in our beer. It’s an important tool to help us blend our beer at Barrelworks.” Admitting that TA has traditionally been used by winemakers—and, increasingly, brewers—to set and reach targets, Richardson “thought it’d be useful information for customers, so we put TA levels on our labels.” For that matter, setting targets was the role of IBU for ages, too. But just try to find a beer drinker today who can’t spout off (rightly or wrongly) about this brewing specification.

Identifying and Explaining Acidity
Acidity, as deftly explained by Richardson, is “a tendency for a molecule to lose a hydrogen proton.” And each type of acid, from lactic to acetic, citric, malic, tartaric, butyric, succinic, pyruvic, and more, makes itself known on our tongues via sourness and tactile sensation. Lactic acid, for example, is perceived as softer, while acetic acid is a volatile acid with a strong taste and smell; it can even make your throat feel scratchy. Malic acid is harsher still.

Rebecca Newman is the quality director at Summit Brewing in St. Paul, Minn. She earned a degree in food science and technology from the University of California-Davis and is an industry veteran with three decades of experience. She’s also one of the 1,300 members of an organization called the American Society of Brewing Chemists, the leading scientific source for the brewing community, worldwide. Newman, who cites sour gummy worms as a personal favorite, points out that, “Sour is not easy to explain, other than it’s a sensation that occupies a space in taste, not flavor … It’s an adjective before the noun, like sour milk, sour dough, sour beer. It’s what happens to something, good or bad, desired or not.”

Acids can come from many different sources, but beer connoisseurs are already familiar with some of the agents introducing tart kicks to favored ales: bacterial microflora such as Brettanomyces, Lactobaccilus, and Pediococcus. Wine and cider have taught us that grapes and apples produce malic acid, but what about the raspberries in a framboise Lambic? They create malic acid, too. And then there’s the citric acid in grapefruit IPAs, the tartaric acid lingering in freshly emptied Chardonnay barrels, and butyric acid, which can contribute unfortunate notes of rancid butter or bile. We’re quick to use the words acid and acidity, but the reality isn’t quite so simple.

Dana Sedin holds a Ph.D. in analytical chemistry and is the lab manager at Colorado’s New Belgium Brewing. He routinely measures pH and Titratable Acidty and can rattle off various acids found at lower concentrations in different beers down to the quinic acid found in New Belgium’s Oscar Worthy Coffee, the coffee-infused version of Oscar, a brown lager conditioned in oak foeders, which itself forms part of the base for the popular sour La Folie. The results of his tests are important from a quality and consistency standpoint, but chromatography and spectrometry aside, Sedin thinks gustatory and olfactory senses still send the best messages, if not measurements, of the experience of drinking acidic beer.

“If you taste each of these acids individually they give you a different perception and aroma,” he says. According to this scientist at least, numbers and figures only tell part of the story.

The Roots of Sour Beer
Lambic brewing dates back to 16th century Belgium, while mass spectrometry has only been around since 1927. “That’s the magic of the Belgians,” says Newman of Summit Brewing. Sour beers can be chromatographed, or separated and displayed to understand their constituent parts, but aren’t they also inherently visceral? Beyond that, it’s tactile. “You feel it,” notes Newman. “Sour you can feel, but it’s on your tongue.”

“No, [Hanssens] does not entertain a lab,” says Matthias Neidhart, president of B. United, importer of several Belgian Lambic brands including Hanssens, a particularly polarizing sour beer. “Their [beers’] natural sourness, acidity, is fully established by nature alone … Each barrel and each season will therefore establish [its] own level and complexity of acidity subject to the level of humidity, temperature, and, of course, each barrel’s [idiosyncrasies].”

Fifth-generation Lambic brewer Jean Van Roy of Cantillon also eschews chemical analysis. “We never use any lab or test to blend our beers,” he says. “In my opinion, you don’t need it if you know your product, if you understand it.”

To the Belgians, understanding acidity is a matter of accumulated experience. “[Traditional Belgians] had their palates for creating consistency batch to batch,” says Firestone Walker’s Crooks. “They didn’t have the technical gadgetry and tools that we have now. Jean Van Roy speaks in terms of weather,” he adds. “[He talks about] the air, changing environments and adapting to it more than he talks about beer making. Frank Boon [of Brouwerij Boon] has got his wood cellar holding something like 30,000 barrels of sour beer. He’s not trying to overthink things. They give nature a lot of responsibility for making these beers. They’re tied more to the Earth.”

The first American brewers to experiment with sour beer styles were naturally influenced by this Belgian approach—waiting, tasting, blending—and even as the science behind the flavors has advanced, some American sour and wild ale brewers are sticking to the old ways. Then again, nearly each one makes contemporary concessions. Cory King, Side Project’s owner, brewer, and blender is partially on board with the modern approach. He notates the pH and TA of his beers, but takes those numbers post-blending. That way, he believes, when you drink Side Project beers like Blueberry Flanders (a Flanders-style Red Ale aged on blueberries) or Balaton (an American wild ale with cherries), “You get to know the blender.”

118featureacidity2Agreeing on a Number
Firestone Walker’s Agrestic, a 6.8 percent oaked American wild red ale, boasts a Titratable Acidty of 7.1 grams per liter (g/L). And while it’s certainly sour, it’s dialed down, tasting quite tannic and not unlike cranberry skin. By comparison, Bretta Rosé is a lighter 5.3 percent framboise yet packs a whopping 12.8 g/L TA. Although the fresh raspberry aroma hints at sweetness, the lactic and malic tartness dominates the taste buds. The numbers don’t lie.

These aren’t Firestone Walker’s least or most acidic beers. Those, according to Crooks, would be Tinaquaic (5 g/L) from the rotating De La Casa series of in-house-only Brett beers and Cowbell, with a TA that reached a whopping 30 g/L. It’s purpose-built for those who have to have more sour. “The first time I put Cowbell on tap,” he says, “right while it was being tapped a guy walked in and said, ‘I wanna try your most sour beer!’”

Just as some fans gravitate toward beers with the highest IBU or ABV, Crooks imagines drinkers one day reaching for sour beers with the biggest TA. According to Crooks’ log, batch one of Cowbell had a TA of 10.71 g/L and a pH of 3.1. With a current pH of 2.9 and a TA of 20 g/L, it’s now primarily used as an acid blending component. Cowbell is an outlier for Firestone Walker, though; the goal of the Barrelworks beers isn’t necessarily sourness for the sake of sourness.

For King’s part, Side Project makes higher acid beers. “I like vibrant tartness,” he explains. “I expect my beers would be more sour.” One sip of Bleuet du Fermier, King’s Chardonnay-aged Saison with blueberries, confirms as much. But he won’t reveal the beer’s TA and can’t envision adding the measurement to his labels. “I tend to be somewhat secretive and I don’t share everything.”

King is intrigued by the idea of devising some sort of consumer-oriented shorthand for sour beer labels, though, as are Newman and Sedin. The fact that Firestone Walker already does so, might mean that the proposal put forth by Crooks and Richardson could eventually become an industry standard. Amusingly, Ron Gansberg, brewmaster at Cascade Brewing in Portland, Ore., has pitched an alternative: IPU. International Puckering Units.

In Colorado, Sedin’s pitch is “to give people an idea of the amount of acid in [the beer], but not [a] specific [measurement].” He proposes printing the ratio of lactic to acetic acid the way New Belgium does internally. For example, the brewery’s pioneering La Folie Flemish-style sour brown has a 28:1 lactic to acetic acid ratio. Eric’s Ale with peaches, for comparison, has a ratio of 44:1. “My general customer is the brewer,” Sedin quickly points out, stressing that more education about sours and acidity is needed. “I have a very different audience.” But Sedin thinks labels should include pH and TA although that still isn’t the whole picture, and presents issues with the federal government, which currently doesn’t regulate beer’s acidity, as it does with wine.

Ultimately, the purpose of listing a sour beer’s TA on its packaging isn’t to brag about its enamel-peeling potential, it’s to educate the consumer and to help classify the varying degrees of tartness in a sour beer. “It’s not a perfect way to measure every acid in our beer,” Richardson admits, but it measures the predominant acid—lactic. And as more sours appear in the marketplace, it might be a step in the right direction. The objective isn’t to standardize the production of sour beers nor is it to come down on the side of consistency versus vintage or acidic variation. It’s to start a dialogue about levels of acidity, and how we taste it, and give drinkers an idea of what they might like and what they might not.

“TA has been used in winemaking since the advent of winemakers looking technically [at their results],” says Crooks. “We’ve been working in Barrelworks around these winemakers for many years … I started this project with the intent to bring science into the realm of this artistic abstract. When you hear the Belgians talk about Lambic, they don’t use technical descriptors. They’re using artistic terms … [There’s] no producer that’s really published anything with scientific knowledge of how to make a consistent Lambic. That’s why I started searching for a better way to define what was happening in our beers,” he says. “There’s no S.O.P [Standard Operating Procedure] for making these beers.” 

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