Proof: The Science of Booze

by Adam Rogers

People sometimes think science is about discovery. But the action in science, the fun part of doing it (or reading about it), isn’t answers. It’s questions, the stuff we don’t know. Behind every step of the process that produces fermented beverages and then distills those into spirits, there is deep science, with a lot of researchers trying to figure it all out.

That’s what this book is about. The bar moment is the culmination of the human relationship with our environment, the pinnacle of our technology, and a critical point for understanding our own bodies, brains, and behavior. William Faulkner is supposed to have said, “Civilization begins with distillation,” but I’d push even farther—beyond just distilled spirits to wine, beer, mead, sake . . . all of it. Booze is civilization in a glass.

Suggestion is a powerful force when it comes to booze,

If you love something, my theory is, you’re supposed to ask what makes that thing tick. It’s not enough to admire the pretty bottles filled with varicolored liquids behind the bar. You’re supposed to ask questions about them—what they are and why they’re different, and how people make them.

Ethanol is one of the few legal drugs of abuse—and the only one that nobody really understands at the functional level. Yet entire businesses—not to mention vast swaths of popular culture—are built around describing the flavors of those drinks and

This book is not a textbook. You can find one if you want; academia is full of people studying yeast, beer, wine, and spirits. You won’t get instructions for building a still or making your own mead here, and neither will you get many recipes for cocktails. (I put in a few of my favorites.)

Understanding our relationship with alcohol is about understanding our relationship with everything—with the chemistry of the universe around us, with our own biology, with our cultural norms, and with each other. The story of booze is one of intricate research and lucky discoveries that shape, and are shaped by, one of our most universal shared experiences. The human relationship with alcohol is a hologram for our relationship with the natural world, the world that made us and the world we made.

Technically, real ale requires a specific variety of yeast that, during fermentation, floats on top of the sugary wort instead of sinking to the bottom.

Yeast was the first eukaryote—that is, the first creature with cells and nuclei—to have its genome sequenced. That was in 1996; biologists were in a rush to see what its DNA looked like because in a way yeasts are the fundamental unit of cell biology.

People called that sediment “yeast” because of its action. The French and German names (levure and Hefe, respectively) derive etymologically from roots meaning “to lift,” as in rising bread. The English “yeast” comes, via the Dutch “gist,” from the Greek word for boiling. Getting the gist of something is literally boiling it down.

a comical description of yeast (“the shape of a Beindorf distilling flask”) fermenting, seen under a microscope: “In short, these infusoria eat sugar, eliminate alcohol from the intestinal tract and CO2 from the urinary organs.” A magical tiny creature that pees carbon dioxide and poops out beer? Please.

Of the strains used for fermentation, the ones from Africa were the oldest, and the vineyard and sake strains had less variation than the others. To Fay, those results suggest the following: humans domesticated S. cerevisiae from African yeast about 11,900 years ago. Sake yeasts came from that same line 3,800 years ago, and vineyard strains 2,700 years ago.

And since yeast are notoriously prone to mutations, new strains would crop up all the time, and preserving the old ones would become a kind of sacred trust. That’s why sourdough starters used to be part of young women’s dowries, handed down from mother to daughter, and it’s why today’s boozemakers tend to return to a preserved, frozen sample of their yeast and grow more instead of just letting the same batch bubble away. It’s why, before Daniel Bacardi fled Cuba in advance of the encroaching revolutionary army in 1960, he destroyed every sample of the fast-fermenting yeast strain that made his rum—Bacardi planned to start over in Puerto Rico, and didn’t want the new Cuban government to have a competing product.

Even when boozemakers look like they’re being casual about their yeasts, they’re not. Brewers of Belgian lambic-style beer ferment in giant, open pools with whatever yeast happens to fall in (as opposed to “pitching” a purchased or carefully maintained strain). Lambics tend to be quite sour, probably because the local microbial flora include the genus Brettanomyces and associated bacteria that excrete acetic acid—vinegar. Usually brewers and winemakers have to follow strict sanitary procedures to keep unwanted microbes with their off flavors out of the ferment. But none of that makes lambic brewers careless about their yeast strains—one brewer, upon being told his fermenting house needed a new roof, panicked. He was sure the yeast colony that made his beer what it was lived in the rafters. So he built a new roof over the old one.

Sugar is the most important molecule on earth. You may think water deserves this title. I get it. Water is really good at dissolving other molecules and carrying them around, both inside our bodies and out in the world. Water lets chemicals bump into each other and then do interesting things. But calling water the Best Molecule is like giving paper the award for Best Book. Water is the medium, a backdrop. Sugar is fuel. It’s the gasoline in our tanks, the molecule that stores the energy that we living things use to stay alive. (And unlike actual gasoline, sugar is water soluble, so our water-filled bodies can move it around easily.)

Technically you have to use Agave tequilana Weber var. Azul—that’s blue agave—and you have to make it in the Tequila region of Mexico. “Tequila,” it turns out, is a controlled appellation, like “Cognac” or “Bourbon.” The regulations say you have to follow certain recipe specifications and be in the right place. And if you try to make the same thing somewhere else? You’re making a different drink. Use Agave potatorum and you’re making mescal. Mix in some fruit and a roasted chicken, and you’re distilling pechuga, which fortunately does not taste like chicken.)

One way to think about sugar is that it’s the way living things store and move carbon. When biologists and science fiction nerds talk about “carbon-based life forms,” this is what they mean. So tomatoes, for example, store carbon mostly as sucrose. Apples use a sugar-alcohol combination. Avocados store carbon not as a sugar but as fat—just like animals do. But grapes are right near the top among fruits in terms of storing carbon as simple, monosaccharide sugars. The fruit is one-quarter sugar, and half of that is glucose.

Most fruits—like, say, apples—make a lot of volatile compounds, especially in the form of the alcohol-acid combinations called esters. But grapes “don’t make a lot of esters at all,”

Wild grapes have both male and female plants; just like animals, some plants reproduce via the exchange of genetic material between the two sexes. That may be the least fun way to think about that process, but the point of it is to swap genes around, to ensure diversity within the species. That’s great if you’re trying to evolve and adapt, but it’s terrible for the person trying to grow and harvest you because of whatever skill set you’ve settled on. That person doesn’t want you to change. So one of the hallmarks of grape domestication is a switch from being dioecious—having a male and a female—to hermaphroditism.

For someone with a contrarian streak, the existence of all those cultivars suggests that grapes weren’t the perfect ingredient for boozemaking we’ve been led to believe. If grapes are so great, why did we need so many different custom versions? That’s the less Panglossian take on grape domestication Myles offers. “They happened to be the juiciest fruit in the Fertile Crescent when everything was getting domesticated,” he says. “If the world’s primary center of cultural development had been in Melanesia it could be that we’d all be sipping on fermented coconut juice and we’d have all these different coconut cultivars with different profiles.” Grapes: What’s the big deal? “These cultivars are frozen in space and time, and the pathogens around them continue to evolve, so the growers bow down to the chemical companies,” Myles says. “We shouldn’t be planting old ones. We should be planting new ones. We should be shuffling up new genetic combinations that are superior.”

He studied the grape genome as a postdoctoral researcher at Cornell University and advocated for the creation of more advanced, newer strains through breeding—just as you’d find with any other commercial fruit or vegetable. But his work in grape genetics went for naught. It takes a long time to develop a new strain, and Myles couldn’t sell anyone on disease-resistant, more flavorful grapes. The winemakers of Europe and California only wanted the same dozen or so strains, familiar from labels. It was “grape racism,” Myles says. So he got out. “I’m in the apple game now,” he says. “We can release a new cultivar, and if it does well, we can make a killing.”

A bottle of beer has 5 grams of CO2 per liter of liquid. A bottle of champagne has 12 grams per liter. When you open one of those bottles, the CO2 inside becomes “super-saturated”—that is, its pressure dissolved in the liquid is higher than equilibrium with the external atmosphere will allow. The CO2 has to come out, which it does by forming bubbles. Now, champagne is pressurized to six times the atmospheric pressure on earth at sea level, enough to propel a popped champagne cork faster than 30 miles an hour. Lesson: letting the cork shoot out of a bottle when you open it is both tacky and dangerous.

He looks at the un-frothy, un-laced glass. “It’s just not washed properly,” Bamforth says sadly. “Or they’re washing these glasses alongside food plates. I don’t know what they’re doing, but they’re not doing it right, because I can tell you the beer, when they brewed it back there, had plenty of foam potential. Ninety-five, 98 percent of foam problems have nothing to do with the beer. It’s everything to do with the way it’s bloody poured.”

Distillers, especially whisky distillers, tell a story of craft and tradition, hundreds of years of practice that defines a culture. But the distilled spirits business is dominated by giant producers who run immensely productive facilities that produce complex, expensive chemical admixtures year after year.

Fermentation is a natural process, as close to a miracle as a science-minded type like me would ever acknowledge. Over human history we’ve learned to harness and adapt it. We domesticated the microorganisms that make it possible, designed containers friendlier to it, created businesses around it. But a winemaker taking credit for fermentation is like a beekeeper taking credit for honey. Fermentation would happen whether men and women were here on earth or not. If a fig spontaneously ferments in the forest, a monkey is there to hear it. (And eat the fig. And get drunk.) Distillation, though, is technology. Human beings invented it; we came up with the process and developed the equipment. It requires the ability to boil a liquid and reliably collect the resulting vapors, which sounds simple. But to do it, you have to learn a lot of other skills first. You have to be able to control fire, work metal, heat things and cool them, make airtight, pressurized vessels. You need a big brain with a wrinkled cortex, maybe some opposable thumbs. But most of all you need a desire to change your environment instead of just live with what you have. Distillation takes intelligence and will. To distill, literally or metaphorically, requires the hubris to believe you can change the world.

“India appears on present evidence to have been the first culture to exploit widespread distillation of alcohol for human consumption.” Yet Allchin’s version isn’t the accepted history. Credit for the still goes instead to ancient Egypt, to an alchemist named Maria Hebraea, more commonly called Maria the Jewess. She was a scientist from the scholarly city of Alexandria sometime between the first and third centuries. And it’s . . . possible. Even though the history is sketchy, Alexandria was the kind of town where a Jewish woman researcher could have invented one of the most important pieces of lab equipment in history.

He called the stuff “fire water,” or aqua ardens. Etymologically the concept lives on in a particular class of high-proof unaged rums from South America, like the cachaça used in cocktails like Mojitos and Caipirinhas. The liquors are called “aguardentes” or “aguardientes”—literally translated, that’s “firewater,” and going by taste they’re aptly named.

Because ethanol is more volatile than water at every temperature, distilling will eventually pull all the ethanol out of a solution—to a point. At 95.57 percent alcohol, the vapor has the same ethanol concentration as the liquid, and you can’t squeeze any more out. It’s called the azeotropic limit, and it’s the upper bound on how potent any spirit can ever be: 194.4 proof. (“Proof” is an old word when it comes to alcohol content; in the United States it’s just twice the percent alcohol-by-volume. “Eighty proof” is 40 percent ABV. In the United Kingdom it has a slightly different calculus—100 proof is 57.15 percent ABV, a definition that comes from the days when British navy rations included rum for sailors. The sailors would mix gunpowder into the rum, and if it ignited when lit, that was proof the alcohol content was high enough to serve.)

The French translated aqua vita into eau de vie, and the Dutch called it “burnt wine,” or brandewijn. Exported to England, that got corrupted to “brandy-wine,” and eventually just “brandy.” The Scots started making the stuff out of grains; in Gaelic, they called it “water of life,” usquebaugh, eventually corrupted to “whisky.”

“If everything goes right, anyone can do this. What experience gives you is how to handle it when things go wrong,” he says. “And things always go wrong.”

THE AIR OUTSIDE a distillery warehouse smells like witch hazel and spices, with notes of candied fruit and vanilla—warm, mellow, and tangy, the aroma of fresh cookies cooling in the kitchen while a fancy cocktail party gets out of hand in the living room.

But “Old Bourbon” referred either to the counties in Kentucky where it came from or to the street in New Orleans on which it became popular—historians disagree on which—not to its manufacturing process.

Wood barrels had shifted from being medium to message. Instead of being mere vessels for transporting beer, wine, and spirits, they became an indispensable part of the process of their manufacture. Something in the wood, combined with time, was the difference between a light, tart, mildly alcoholic grape juice and a mellow, rounded wine—between moonshine and bourbon, between tequila blanco and tequila añejo.

Four years of aging on Scotland’s west coast can actually result in a gain of five liters of water. In chilly wine caves and the low, single-story warehouses of cold, damp Scotland, barrels lose more ethanol; in the hotter American South, they tend to lose water—a factor exacerbated by the metal-sided rickhouses. They get much hotter on the high floors, which is why “small batch” or “single barrel” bourbon can be so interesting—those casks are selected for being accidentally better than the barrels around them.

Can you get even crazier? The answer in boozemaking is always yes. If you don’t care about getting the appellations of your region—if you don’t mind not being able to call yourself “bourbon” or “Scotch whisky,” then you can stop chopping down oak trees and look for something more exotic. A cooperage called Black Swan, based in Minnesota, makes barrels and liner inserts out of nontraditional woods, bored into a honeycomb pattern to increase surface area.

The global popularity of whisky is squeezing those makers—more and more of them are switching to bottles with, as they say in the trade, no age statement. They don’t say how old it is, because their marketing has equated age with quality, and what’s in the bottle now includes spirit from younger barrels because they don’t have anything else to sell. As rum researcher Rafael Arroyo wrote in 1945: “The ever increasing demands of the trade, the lack of adequate working capital, the anxiety for immediate returns, immoderate and unfair competition and many other influences of businesses compel the manufacturers to place their products on the market in the shortest possible time.” So every producer of booze, major and craft alike, has a common fantasy: make something that tastes old without aging. As early as 1817, the industrial handbook The Cabinet of Arts, for example, recognizes in its chapter on brewing and distilling that time is the most important component of the flavor of fine French brandy. Its authors then go on to suggest that you should totally fake it. Distill a spirit as pure and flavor-free as possible, they say, and then add “oil of wine”—a wine concentrate—and some treacle or caramel for color. Presto! All the brandy, none of the wait.

Tuthilltown has one more move. Figuring that increased contact between liquid and wood was a good thing—and recalling that in Scotland, warehouse managers roll their barrels and move them from higher racks to lower ones to rotate among all the environmental conditions in the racks—Gable’s father Ralph came up with the idea to play music with a lot of bass to the barrels, to stir up their contents. The distillers moved speakers into the warehouse, a 1788 gristmill, and at night cranked up A Tribe Called Quest and dubstep. “We started noticing really deep flavors and aromas,” says Erenzo. “We call it our sonic barrel maturation process.”

Jefferson’s Ocean bourbon ages for almost four years on a boat. On the water. The idea being, getting sloshed around by the waves exposes more of the liquid to the wood more rapidly—and your angels’ share losses are replaced by briny, sea-scented air. It gets good reviews.

“What our technology does better than any of those is the removal of congeners. Our gas chromatographs show significantly greater reduction in the minor alcohols and free radicals than any of the other three methodologies can achieve. The flavors, whether you’re talking about cactus for tequila or sugar cane for rum or grain for bourbon or Scotch, are more apparent.” In eight hours, he says, new-make bourbon tastes like it spent six years in the rickhouse. All fully patented, of course.

The straight bourbon is, as Hewlette promised, very good. The six-month-old was the equal of any small-distillery, small-barrel-aged bourbon I’ve had, which is to say, it had the over-oaked taste of 1990s California Chardonnay and a little bit of the green, short-chain tannin of any brown liquor that hasn’t spent enough time oxidizing. But for something that hasn’t been through a traditional aging process, that’s actually kind of impressive.

Now, to be fair, Quandt doesn’t really think anyone, no matter how expert, can produce an objective assessment of a wine’s quality, origins, manufacture, or taste. Because that’s what his data tells him. “We are eight guys who are pretty experienced and have been doing this together for twenty years, and yet when we do the statistical analysis of our tastings, the amount of disagreement is extraordinary,” Quandt says. “Since people don’t have identical utility functions, they evaluate different characteristics of the wine. As a result, a wine that tastes fantastic to one person will taste shitty to another one. In a sense, it’s hopeless.” You might even think that over time the members of the Liquid Assets group would have learned from each other and learned more about wine. If that was true, their amount of intra-group agreement would have increased, even if they didn’t agree with outsiders. But no dice. The numbers show they disagree with each other today as much as they did twenty years ago. In fact, they pride themselves on it. The difference between Quandt’s group and professional wine reviewers, then, is that the pros attempt to disguise their subjectivity with—well, put it this way: Quandt’s paper on the subject for the Journal of Wine Economics is called “On Wine Bullshit”: Since there are many wine writers, and there is a substantial overlap in the wines they write about (particularly Bordeaux wines), it is important that there be substantial agreement among the...

Quandt thinks that pros like Parker—or your friend who always makes a big show over the wine list at a restaurant—are essentially making it all up. Or, like some storefront psychics, possibly they think they know what they’re talking about, when in actuality they’ve merely intuited their way into a con. “I find it impossible to imagine that somebody can take a composite impression of a wine and decompose it into eight components and identify each one individually—a little bit of tobacco and a little of honey flavor and a little bit of citrus and a little bit of wet earth and a little bit of molding bushes,” Quandt says. Way back in 1937, the humorist James Thurber stuck it to this kind of pompous, meaning-free connoisseurship in a New Yorker cartoon showing a wine taster saying of a glass, “It’s a naive domestic Burgundy without any breeding, but I think you’ll be amused by its presumption.” A wonderful Roald Dahl short story, “Taste,” from 1951, similarly depicts a hyper-verbal wine snob as a con artist and a fraud. If you really want to blame someone for the wine world’s excesses of verbal fluff, you might point a finger at the writer Pamela Vandyke Price. Her 1975 book The Taste of Wine popularized such descriptors as “forthcoming,” “pinched,” “sloppy,” and “vivacious” as opposed to something more specific, or more chemical. Booze reviewers have been doing the same thing ever since.

Hahahahahahahahahaa. Exactly.

But smell and taste are different. For those senses, the hard philosophical and scientific work is trying to find words that we recognize in common and can share with each other, so that we all know what we’re talking about. The first step is to acknowledge just how limited our senses actually are. For example, it’s possible to ask how many different aromas a person is able to perceive at once—like when taking a sip of wine. In 1998, a couple of Australian researchers, Andrew Livermore and David Laing, hypothesized that even if people could identify the smells of complicated things like coffee or kerosene within a second or two, those same people wouldn’t be able to identify any of the hundreds of components of those same scents.

The specific smells they chose—smoky, strawberry, lavender, kerosene, rose, honey, cheese, and chocolate—were listed on a computer screen. The only thing their twenty-six volunteers had to do was sniff the air coming from an exhaust port and say which thing they were smelling. With between one and four components, the subjects confidently and quickly picked out the smells in the mix. But if the mixture had more components, they slowed way down . . . and their accuracy dropped to nothing. After four different smells, the human brain basically chunks them all together, and that gestalt aroma becomes the identifying smell for a given object.

A study titled, simply, “The Color of Odors,” will destroy your faith in anybody’s ability to taste anything. Here’s how it worked: three French researchers started with two wines from Bordeaux, a white made with Sémillon and Sauvignon grapes and a red made with Cabernet Sauvignon and Merlot. The researchers first had a group of subjects taste both the white wine and the red, under white light in clear glasses, and write down all the words they could think of to describe each one. In this test it didn’t matter whether the tasters perceived the same things. Inter-rater reliability wasn’t a factor here—the researchers didn’t care if tasters agreed with each other about the wine color and taste, just that each taster would consistently call one “red” and one “white.” Then the researchers took an odorless, tasteless extract of the grape-skin pigment anthocyanin and dripped it into the white wine, turning it red. And they called the tasters back for a second go-around, asking them to compare the white wine and the colored wine—the same wine, in other words, with red food coloring. The result was a taste-test catastrophe. Almost to a person, the tasters chose to use the same words for the white wine from the initial tasting on the white wine in the second. And they used the same words for the red wine on the red-colored white wine. They simply could not tell the difference. Color alone—not aroma, not flavor—told them what to expect, and that’s exactly what they tasted.

I’m going to own up—while I have a pretty good palate for brown liquor, when it comes to wine I’m not much better than “yes, that’s good” and “no, I don’t like that one.” I’ve never had the knack.

“We tentatively suggest that the verbal skills, which are developed around wine, perhaps lead to a somewhat similar overestimation of confidence in expertise,” the researchers write. They’re hinting that knowing many words to describe wine makes people think they’re better at identifying it than they really are. So go strong to the hoop with that wine list next time you’re at a fancy restaurant, because the odds are the sommelier isn’t a whole lot better at discriminating among wines than you are.

By the way, those taste buds aren’t organized into any kind of map, the way you might have learned as a kid. Not only are the four basic tastes—sour, salty, sweet, and bitter—perceived all over the tongue, but some cells pick up a fifth taste, meaty umami. And some flavor scientists think more basic tastes remain to be characterized. One candidate: kokumi, or fattiness.

How do we taste something super-complex like wine or rum? The answer is in the nose. Flavor is a combination of taste and smell.

Some researchers think that if you don’t chew and swallow, you’re limiting perception. That might deeply screw up tests where the subjects spit out the tastant—like, for example, wine tasting.