Gastropod: Sonic Seasoning

“Sound is the forgotten flavour sense,” says experimental psychologist Charles Spence. In this episode of Gastropod, we discover how manipulating sound can transform our experience of food and drink, making stale crisps taste fresh, adding the sensation of cream to black coffee, or boosting the savory, peaty notes in whiskey.

Composers have written music to go with feasts and banquets since antiquity—indeed, in at a particularly spectacular dinner hosted by Duke Philip of Burgundy in 1454, twenty-eight musicians were hidden inside an immense pie, beginning to play as the crust was opened. Today, however, most chefs and restaurants fail to consider the sonic aspects of eating and drinking. That’s a mistake, because, as we reveal in this episode, sound can affect how fast we eat, how much we’re prepared to pay for our meal, and even what it tastes like.

Don’t believe us? Here are three simple sonic seasoning tricks to try at home.

The Sonic Chip

This experiment, for which Charles Spence won a highly coveted IgNobel prize in 2008, came about almost by accident.

Spence was working with a big company to see whether they could use the recently discovered “parchment skin” illusion to trick customers’ brains into believing that their clothes felt even softer after coming out of the washing machine. It works this way: if you muffle the sound of your hands being rubbed together while you’re rubbing them, your brain assumes that they must be smoother than they are. That’s because your brain combines the audio information with the tactile sensation and assumes because there’s less noise, there’s less friction, and hence softer skin.

This idea—that if you change the input in one sensory realm, you can influence perception in another—is called crossmodal sensory interaction, and it lies at the core of Spence’s research.

“Food and drink are among life’s most multisensory experiences,” Spence pointed out, so it’s perhaps hardly surprising that it occurred to him that the parchment skin illusion might work in the mouth, using food rather than clothing.

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He recruited 200 volunteers willing to eat Pringles for science, and played them modified crunching sounds through headphones, some louder and some more muffled, as they ate. And he found that he could make a 15 percent difference in people’s perception of a stale crisp’s freshness by playing them a louder crunch when they bit into it.

“The party version” of this trick, according to Spence, was developed by colleagues in the Netherlands and Japan. Volunteers were asked to crunch on crisps in time with a metronome, while researchers played crunching sounds back, in perfect synchrony, through their headphones. All was well until the researchers replaced the crunching with the sound of breaking glass—and “people’s jaws just freeze up.”

Have a packet of crisps that’s been sitting around too long? Here’s the sonic boost they need.

And—thanks, science!—here’s a soundtrack to make your perfectly fresh crisps taste stale.

As far as breaking glass goes, we can’t condone inflicting that kind of trauma—you’re on your own.

Hot and Cold

Listen to this recording of two drinks being poured into a glass, back to back. Can you tell whether each drink was hot or cold? (Scroll down to the end of this section for the answers.)

According to Spence, you should be able to guess. The human ear is sensitive enough to pick up on the slight change in a liquid’s viscosity as it changes temperature. Hot water is less viscous than cold, which means that the splash it makes when it hits the bottom of the glass or mug is a tiny bit splashier—and thus higher pitched.

This finding has practical applications in advertising, for example, as well as drinks dispensers—your soup or coffee could be made to seem piping hot, or your soda even more cool and refreshing. But Spence also suggests playing with it: blindfolding guests and handing them a cold drink while playing the sound of a hot one.

The result? With the sound, “we’ve put the idea in your mind, the expectation that it’s going to be very hot,” he explains. “And then when you put it to your lips and it’s suddenly cold, you’ll be shocked, but you probably won’t know quite why you should be shocked.”

(Answer: the first pour was cold, the second was hot.)

Bittersweet Symphony

So far, we’ve focused on the sound that food makes, either in your mouth or in the glass. But Spence’s recent research has focused on something much more abstract and mysterious: an implicit association between particular kinds of sound and tastes.

The idea that different scents, tastes, and flavours might correspond to different musical notes has a long, if speculative, history: in nineteenth-century London, perfumer Septimus Piesse created a scent scale in which middle C was matched with rose, while an octave lower was geranium. In the following decades, novelists picked up on the idea and invented fictional liqueur flavour keyboards (Joris-Karl Huysman’s Against Nature), a “pianocktail” machine (Boris Vian’s L’Ecume des Jours), and a scent organ (Aldous Huxley’s Brave New World).

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On the left, a diagram of the pianocktail created by Florica Vlad; on the right, a mechanical version of the pianocktail built by musician Géraldine Schenkel.

According to Spence, the first scientist to test the concept, however, was Kristian Holt-Hansen, working in Denmark. Using Carlsberg’s lager and Elephant beer as his two test beverages, he demonstrated that people consistently matched a lower-pitched tone (510-520 Hz) to the lager, and a slightly higher note (640-670 Hz) to the more vinous Elephant beer. He then found that when he played the matching sound to people as they consumed the appropriate beer, they rated it as tasting better.

As unlikely as it sounds, Canadian scientists successfully replicated the experiment in 1984, with the confusing addition of grapefruit and dill pickle, which matched even higher pitched sounds (1016 Hz and 1394 Hz, respectively).

That was the state of the science when Charles Spence decided to test the connection between pitch and taste in 2012. Using a bittersweet toffee specially created by chef Heston Blumenthal, Spence and his colleagues showed that people perceived the toffee as ten percent more bitter while listening to low-pitched notes, and ten percent sweeter when their headphones were filled with higher-pitched music. Subsequently, Spence says he’s tried this experiment on people from all over the world, and found a similar correspondence.

You can try it at home with some bittersweet dark chocolate and these two soundtracks. The first one is sweet-enhancing, the second will boost bitter.

But, although the effect is real, the mechanism behind it is more elusive. Listen to this episode of Gastropod to understand how and why sound affects our experience of food—and how we might use that science to redesign the experience of eating. From chefs playing with sonic seasoning to enhance our dinner, to the perfect soundtrack for whiskey, we explore the way our brains combine sound with our other senses to create flavour.

This is the second in a two-part series exploring the relationship between sound and food: don’t miss the previous episode of Gastropod for much more on the experimental history and emerging science of acoustic agriculture, from the perfect bovine playlist to the lost rhythms of Southern farming. And, if you like what you hear, please support our work with a donation of any size.

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Gastropod: Field Recordings

Plants that can hear themselves being eaten. Microphone-equipped drones that eavesdrop on sick chickens. Lasers that detect an insect’s wing-beats from dozens of feet away.

In this James Bond-inspired episode of Gastropod, we listen to the soundtrack of farming, decode the meaning hidden in each squawk, moo, and buzz, and learn how we can use that information to improve our food in the future. Tune in now for this special broadcast of the barnyard orchestra!

Mozart for Plants

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IMAGE: Retired dentist George Milstein’s 1970 album claims to help plants grow (you can listen to it here).

The idea that plants can hear and respond to music has a long and chequered history. Charles Darwin made his son, Francis, play the bassoon in front of a herb while he watched to see whether its leaves twitched (the plant was unmoved); Barbra Streisand caused a veritable explosion of colour when singing to her tulips in the musical On a Clear Day You Can See Forever; and, as recently as the 1970s, UNC Greensboro physicist Dr. Gaylord Hageseth claimed that his experimental “pink” noise could make turnips sprout much faster.

While the claims that playing Mozart in a cornfield will lead to a dramatic increase in yield have proved impossible to replicate, scientists are sure that plants do respond to sounds in their environment, with small changes in gene expression, for example, or slightly different germination rates.

But, as Heidi Appel, senior research scientist at the University of Missouri, told Gastropod, “we never understood why plants would have that ability.”

Pest Sounds

Intrigued, Appel teamed up with her colleague Reginald Cocroft, a behavioral ecologist, to focus on a sound that, they thought, might be particularly useful to plants: the vibrations caused by insect feeding.

“These are one of the earliest and most quickly transmitted signals plants have that they’re being attacked,” Appel told Gastropod. And while plants can’t hear insects the same way we do—they don’t have ears, after all—they can sense vibrations, much like club-goers feel the thump of bass or worshippers hear an organ reverberate through a church. “In that case, your body is a substrate,” picking up the sound vibrations, Appel explained. “That’s much more like what plants experience.”

To test their theory, Appel and Cocroft used lasers to measure the minute leaf tremors, about 1/10,000th of an inch, that caterpillars make when they munch on Arabidopsis (rockcress), a spindly relative of cabbage and broccoli that is commonly used in plant research. Next, they played those sounds back to one set of plants, and left the control group in peace. Finally, they let the caterpillars loose on both plant populations.

Astonishingly, they found that the plants that had undergone audio training actually responded to the attack by producing much higher levels of mustard oil, their innate pesticide—which made them much less appetizing to the hungry caterpillars.

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IMAGE: A caterpillar and laser on an Arabidopsis plant; still photo from a video made by Roger Meissen.

“That was very exciting and we were very happy,” Appel said. “But, at one level, we thought, ‘So what?’ Plants might respond to everything.”

So they tested the plants again, this time using recordings of wind and treehoppers, a bug that looks like a thorn and sings with a high-pitched whine but does not like to dine on Arabidopsis. In response to these vibrations, however, the plants produced no increase in mustard oil. With this elegant experiment, Appel and Cocroft had solved a basic question of plant evolutionary biology: plants evolved the ability to respond to sound vibrations in order to recognize and ward off attackers.

Musical Mustard

In doing so, Appel and Cocroft may have also hit upon a potent environmentally-friendly pesticide. Perhaps a field full of speakers blasting the sounds of crunching caterpillars might help terrified crops prime themselves to ward off a real attack, removing the need to apply chemical pesticides. This summer, Appel and Cocroft are testing commercially useful Arabidopsis relatives in the brassica family, such as kale and Brussels sprouts, to see if they demonstrate the same response.

But, as Appel pointed out to Gastropod, the use of sound might have an even more direct impact on our health. While plants evolved these chemical responses to deter pests, for humans, they often provide both flavour and health benefits. In fact, the sulfurous compounds produced by Arabidopsis and its fellow brassicas form the basis of America’s favorite hot dog condiment, mustard. And those same chemicals are actively being studied by cancer researchers for their potent health benefits.

Maybe, by playing predator sounds in the field, farmers could actually grow more healthful plants.

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IMAGE: Recording caterpillar munching; still photo from a video made by Roger Meissen.

Appel is testing this hypothesis with an African plant that is currently harvested for medicinal use, to determine whether caterpillar feeding will increases the plants’ production of beneficial chemicals. If so, she can then test whether playing predator sounds has the same effect.

“When we look at a plant as a source of flavour or medicine, what we are looking at is the product of millions of years of evolution of the plant interacting with its own pests—and those are largely insects,” said Appel. Insects that, it turns out, plants can hear.

This is the first of a two-part series exploring the relationship between sound and food. Listen to this episode of Gastropod for much more on the experimental history and emerging science of acoustic agriculture, from the perfect bovine playlist to the lost rhythms of Southern farming.

And, if you like what you hear, subscribe to make sure you don’t miss out on hearing the difference between hot and cold tea, learning how the sound of tiny bubbles in soda changes its taste, and discovering the science behind pairing wine with music. If you’re feeling particularly generous, you can also make a donation to help Gastropod keep going—thank you!

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IMAGE: Wayne Daley and Casey Ritz (professor of poultry science at University of Georgia, Athens) preparing to record chicken vocalizations. Photo credit: Gary Meek.

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Los Angeles à la Carte

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IMAGE: Ollie Hammond’s, 3683 Wilshire Blvd., Los Angeles, 1950. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

Restaurant menus seem like the most ephemeral of ephemera: updated seasonally or even daily; printed in-house on cheap card stock or even scrawled on chalkboards. But, with menus as with fruit stickers, airsickness bags, and pizza boxes, everything humanity sees fit to print will eventually attract a collector or two. Many of these menu collections are now archived in public institutions, where they have proven themselves to be a valuable resource for historians, designers, economists, chefs, and even ecologists.

The New York Public Library’s collection of roughly 45,000 menus leads the pack, and is currently being transcribed and geo-tagged by volunteers from all over the world. The Los Angeles Public Library’s collection is smaller, but, as it turns out, no less fascinating. USC professor Josh Kun has spent the past couple of years sifting through it with his students, and the resulting exhibition, “To Live and Dine in L.A.,”  launches today.

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IMAGE: Los Angeles Chamber of Commerce Banquet Menu, 1895. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

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IMAGE: Scrivner’s (various locations), 1950s. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

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IMAGE: Forbidden Palace, 451 Gin Ling Way, Los Angeles, 1940s; Kowloon, 6124 W. Pico Blvd., Los Angeles, 1959. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

In the accompanying book, Kun tells the city’s history through its menus, from its geographic growth to the arrival of different immigrant groups, and from the rise of the automobile to the origins of the farm-to-table movement.

I interviewed Kun and wrote about the project for the New Yorker, and our conversation includes his introduction to the weird subculture of menu collector swap meets as well as his “white whale” menu—the one that got away.

It was from the Los Angeles Women’s Saloon and Parlor, in East Hollywood, which opened in 1974 and was, Kun writes in the book, “the first, and last, feminist restaurant in the city.” To quote myself:

A 1976 Times description of the restaurant offers tantalizing references to omelettes, crab quiche, and vegetarian meatloaf, as well as to an absence of diet drinks (to promote size-acceptance) and grapes and lettuce (to support California farmworkers). But Kun’s searches failed to turn up a surviving menu.

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IMAGE: “Mary Yakutis prepares steamed vegetables at the Los Angeles Women’s Saloon and Parlor,” New York Times photo.

Kun did, however, inadvertently uncover some family history during the research process, while trying to track down a menu from the Budapest Hungarian Restaurant on Fairfax. His grandfather, who immigrated to Los Angeles from Nazi-occupied Hungary, had, for a short time, part-owned the restaurant.

“One of my graduate students tracked down the guy who had bought the restaurant and he kept the one menu,” Kun explained. “I knew my grandfather was a waiter, a busboy—he always worked in restaurants—but I never knew he owned one!”

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IMAGE: Budapest Hungarian Restaurant, 432 N. Fairfax Ave., Los Angeles, 1960s. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

Despite spending more than a year tracing aesthetic, socio-cultural, geographic, and culinary patterns through the city’s menus, when I asked Kun to describe the distinctive features of an Angeleno menu, his conclusion that there was no such thing—that the city’s menus mirror the heterogeneity of the dozens of separate cities, towns, and communities that together make up Greater Los Angeles.

That said, he mentioned a collector had told him that “the only thing that makes an LA menu an LA menu is that they’re typically really big”—both in terms of dimensions and the sheer quantity of dishes listed. The city and its dining choices are, it seems, united by sprawl.


IMAGE: The Broadway, Broadway and Fourth Streets, Los Angeles. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

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IMAGE: Al Levy’s Grill, 617 S. Spring St., Los Angeles, 1930s. From To Live and Dine in L.A.: A Century of Menus from the Collection of the Los Angeles Public Library by Josh Kun, published by Angel City Press.

There’s much more in my New Yorker article, including Kun’s thoughtful analysis of the archive’s gaps: check it out here.

Kun’s book, To Live and Dine in L.A.: Menus and the Making of the Modern City, is utterly gorgeous: it contains full-colour reproductions of hundreds of menus, a handful of fascinating menu “re-mixes” by celebrity chefs Nancy Silverton, Micah Wexler, Susan Feniger, and others, as well as an essay on Los Angeles menu design by LACMA’s Staci Steinberger, another by celebrated Angeleno food critic Jonathan Gold, and, of course, Kun’s own contribution. And the exhibition and associated program kick off today: visit the Los Angeles Public Library’s website to find out more.

Thanks to Geoff Manaugh for the tip. As a reminder, my writing can regularly be found on the New Yorker website these days: recent stories include an investigation into the mysterious origins of Swiss cheese holes, a visit to the International Cocoa Quarantine Centre in Reading, and a review of the smell of Qadaffi’s death.

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Smog Meringues

The concept of terroir will be familiar to most Edible Geography readers; recently, we also explored the idea of “merroir,” or tasting place in sea salt. But what about aeroir—the atmospheric taste of place?

GenevaSmog_10 London peasouper CREDIT Center for Genomic Gastronomy

IMAGE: A London-style Peasouper Smog Meringue. Photo by the Center for Genomic Gastronomy.

This afternoon, the Center for Genomic Gastronomy and I will be offering New Yorkers a chance to taste aeroir, with a side-by-side tasting of air from different cities. With the support of the Finnish Cultural Institute in New York, we have spent the past few months designing and fabricating a smog-tasting cart, complete with built-in smog chamber, as well as developing a range of synthetic smog recipes.

Having made its debut at a meeting of the World Health Organization in Geneva a fortnight ago, the cart will be stationed on Rivington Street, just off the Bowery, from noon to six today. We will be serving up free smog meringues from three different locations as part of the New Museum’s IDEAS CITY street festival.

The cart builds on an earlier project by the Center for Genomic Gastronomy. In 2011, after reading that an egg foam is ninety-percent air in Harold McGee’s bible of culinary chemistry, On Food and Cooking, the Center took whisks, mixing bowls, and egg whites out onto the streets of Bangalore, using the structural properties of meringue batter to harvest air pollution in order to taste and compare smog from different locations around the city.

IMAGE: Harvesting urban air pollution using egg foams. Photo by the Center for Genomic Gastronomy.

I’ve been a fan of the Center’s work for a while (I included their publication, Food Phreaking #001, in my best books list for 2013), and, inspired by their smog meringue project, I began to speculate about the concept of “aeroir,” and the idea that urban atmospheres capture a unique taste of place.

As we started to work together, I visited the atmospheric process chambers at the Bourns College of Engineering, at the University of California, Riverside, to see how scientists actually recreate smog conditions in the lab, in order to study the relationship between emissions and atmospheric chemistry.

1 New mobile UCR Smog Chamber

IMAGE: Mobile smog chamber, UC Riverside CE-CERT. Rows of UV lights are used to “bake” the smog. Photo by Nicola Twilley.

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IMAGE: Deflated Teflon bags hand in the large atmospheric emissions chamber room at UC Riverside CE-CERT. The mirrored walls reflect UV light to ensure the smog “bakes” evenly. Photo by Nicola Twilley.

During my visit, a group of students was setting up an agricultural smog, which is characterised by ammonia and amines from feedlot manure lagoons and other organic waste. These combine with NOx and incompletely combusted hydrocarbon emissions from cars, power plants, and industry to give the Central Valley of California, for example, some of the worst air quality in America.

We watched as a team injected precise amounts of different precursor chemicals into a gigantic Teflon chamber, where they would be cooked under hundreds of UV lights in order to catalyse the reactions that create smog. The students were hoping to characterise those reactions, in order to understand the entire chain of chemical processes leading to smog formation, and then design and test ways to prevent or mitigate against it.

With advice from Professor David Cocker and Mary Kacarab at UC Riverside, the Center for Genomic Gastronomy and I worked out how to build a DIY, mini-smog chamber. We then developed and tested recipes using readily available precursor ingredients in create a variety of different smogs.

GenevaSmog_03 Cart CREDIT Center for Genomic Gastronomy

IMAGE: Smog tasting cart set up in Geneva, at a meeting of the World Health Organisation. Photo by the Center for Genomic Gastronomy.

GenevaSmog_07 Terpenes precursor CREDIT Center for Genomic Gastronomy

IMAGE: Emissions from these precursor chemicals are pumped into the cart’s chamber and exposed to UV light to create a synthetic smog. In this image, pine needs and orange peel provide terpenes to simulate a biogenic smog. Photo by the Center for Genomic Gastronomy.

After running around New York City in order to source our precursor ingredients (a huge thanks to Kent Kirshenbaum, chemistry professor at NYU and co-founder of the Experimental Cuising Collective), we spent Thursday afternoon and evening in the kitchens of Baz Bagel (excellent bagels, amazing ramp cream cheese, and truly lovely people) assembling the cart, mixing different chemical precursors, and then “baking” them under UV light to form a London peasouper, a 1950s Los Angeles photochemical smog, and a present-day air-quality event in Atlanta.

We chose these three places and times to showcase three of the classic “types” that atmospheric scientists use to characterize smogs: 1950s London was a sulfur- and particulate-heavy fog, whereas 1950s Los Angeles was a photochemical smog created by the reactions between sunlight, NOx, and partially combusted hydrocarbons. Present-day Beijing often experiences London-style atmospheric conditions, whereas Mexico City’s smog is in the Angeleno style.

Precursor chemicals

IMAGE: Diesel and NOx, two precursor chemicals. Photo by Nicola Twilley.

Meanwhile, at its worst, Atlanta’s atmosphere is similar in composition to that of Los Angeles, but with the addition of biogenic emissions. An estimated ten percent of emissions in Atlanta are from a class of chemicals known as terpenes, from organic sources such as pine trees and decaying green matter. We had also hoped to create a Central Valley smog as well, but time got the better of us.

Each city’s different precursor emissions and weather conditions produce a different kind of smog, with distinct chemical characteristics—and a unique flavour.

Whisking smog

IMAGE: Whisking meringues inside the smog chamber at Baz Bagel on Thursday. The long gloves were sourced at a sex shop, hence the fetching black vinyl. Photo by Gabe Harp.

As it turns out, Arie Haagen-Smit, the man known as the “father” of air pollution science, was originally a flavour chemist who rose to prominence thanks to his work on pineapples. Nadia Berenstein, the flavour historian I interviewed for a recent episode of Gastropod, pointed me to a speech Haagen-Smit gave in the 1950s, explaining his shift in research from fruit flavours to smog science to a room full of his former colleagues. In it, he explains, “I am engaged at the present time on a super flavor problem—the flavor of Los Angeles.”

I can confirm, based on Thursday night’s bake-off, that the different cities’ smogs do, indeed, taste different (and yet equally disgusting).

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IMAGE: Gabe Harp piping “London” mini-meringues in the kitchen at Baz Bagel. Photo by Nicola Twilley.

Inhaling smog over extended periods is extremely damaging to human health. In New York City, which has the 12th worst ozone levels in the nation according to the American Lung Association’s Annual “State of the Air” report, air pollution levels are highest in neighborhoods that are majority non-white and low-income—a particularly insidious form of environmental injustice. By transforming the largely unconscious process of breathing to the conscious act of eating, the smog-tasting cart aims to create a visceral, thought-provoking interaction with the air all around us.

One of my collaborators, Zack Denfeld of the Center for Genomic Gastronomy, reports that during previous installations and performances of the Center for Genomic Gastronomy’s Smog Tasting project, the most frequently asked question has been: “Is this safe to eat?” His typical response is, “Well, is it safe to breathe?”

Unsurprisingly, there is not a lot of research on the impact of eating polluted air, as opposed to the more common method of exposure, breathing it. However, the scientists we have spoken to have pointed out that the human digestive system is more robust and better able to deal with these chemicals than our respiratory system—and that the trace amounts captured in a mini-meringue make for a very small dose, in any case.

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IMAGE: Zack Denfeld pumping precursor emissions into the smog chamber. We didn’t assemble the entire cart at Baz Bagel, due to space constraints. Photo by Nicola Twilley.

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IMAGE: Smog “baking” in the chamber at Baz Bagel. Photo by Nicola Twilley.

In any case, our hope is that the meringues will serve as a kind of “Trojan treat,” creating a visceral experience of disgust and fear that prompts a much larger conversation about the aesthetics and politics of urban air pollution, as well as its health and environmental effects. Eat at your own risk!

This smog-tasting cart is intended as the start of a larger collaboration exploring the concept of “aeroir.” After all, air is the site at which we have an intimate, constant interaction with a geographically specific manifestation of urban planning, economic activity, environmental regulation, and meteorological forces. We hope to develop a multi-sensory series of installations, devices, and performances to make that interaction sense-able.

For example, we imagine that air quality could function as a kind of culinary constraint that inspires new kinds of regional cuisine, aided by the development of smog flavour wheels. Working with scientists who are measuring how smog affects the human sense of smell, as well as chefs, we could imagine developing a menu of street food pairings for particular atmospheric conditions.

Equally, we hope to partner with engineering labs to create novel wearable technologies that add olfactory and trigeminal stimulation to any eating experience—a sort of “smog seasoning.” Aeroir may well be the missing ingredient that makes tacos taste the same in the restaurant back home as they did on the streets of D.F.

The overlap between culinary technology and atmospheric conditions is literal as well as metaphorical. During my visit to UC Riverside, I visited their new Cooking Emissions Laboratory at UC Riverside to explore new research into the impact of “burger smog” on urban air quality—something I will be reporting on at greater length in the coming weeks.

GenevaSmog_01 Atlanta Meringues CREDIT Center for Genomic Gastronomy

IMAGE: Atlanta-style smog meringues as served in Geneva. Photo by the Center for Genomic Gastronomy.

With their original smog meringue insight, the Center for Genomic Gastronomy opened up a powerful method to translate quantitative environmental data and the scientific understanding of pollution and physiology using the images, metaphors, and tools of food and cuisine. It’s a thrill to work with them to explore its potential.

The smog-tasting cart will be serving smog meringues on Rivington Street between Bowery and Chrystie from noon today until 6 p.m. (or whenever supplies run out), as part of the New Museum’s IDEAS CITY street festival, directed by the legendary Joseph Grima. Our participation is made possible thanks to the support of the Finnish Cultural Institute in New York, as part of their 25th Anniversary program, which focuses on the theme of urban nature. Scott Wiener, pizza tour leader extraordinaire, connected us to Baz Bagel, who let us use their kitchen when the day’s bagel rolling, boiling, and baking was done. Scientists David Cocker, Mary Kacarab, Kent Kirshenbaum, and Darby Jack have been all been exceedingly generous with their time and expertise as well as very tolerant of our weird approach to their field of research. As always, thanks also to Geoff Manaugh, who accompanied me on my visit to UC Riverside and helped discuss the concept of aeroir.

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Gastropod: The Cocktail Hour

Whether you sip it with friends, chug it before hitting the dance floor, or take it as a post-work pick-me-up, there’s clearly nothing like a cocktail for bracing the spirit.

In addition to its peculiar history as a medicinal tonic, plenty of hard science lies behind the perfect cocktail, from the relationship between taste perception and temperature to the all-important decision of whether to shake or stir. What’s more, according to historian David Wondrich, mixology is “the first legitimate American culinary art”—and one that has since caught on around the world.

Raise a glass, and listen in as Gastropod discovers the cocktail’s historical origins, its etymological connection to a horse’s butt, and its rocky history, post-Prohibition. We also check out an original copy of the world’s first cocktail recipe book at New York City’s bartending mecca, Cocktail Kingdom; take a private cocktail science class with Jared Sadoian of The Hawthorne in Boston; and talk red-hot pokers with culinary scientist Dave Arnold. Cheers!

The Secret Ingredient No Cocktail Should be Without
It might seem counterintuitive, but, in a world overflowing with fancy bitters and spherical ice makers, the thing your cocktail is missing is actually much simpler: salt. Dave Arnold, the mixologist behind high-tech cocktail bar Booker and Dax, shared this secret with Gastropod. It’s just one of several scientific tricks contained in his new book, Liquid Intelligence: The Art and Science of the Perfect Cocktail.

Of course, the most important ingredient in a cocktail is the liquor. The sugar, acids, and ice choices also have flavor implications, making every cocktail recipe into a kind of calculus that factors in the physics of energy transfer as well as variations in the molecular structures of different sweeteners.

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Cocktail construction chart, created by the U.S. Forest Service in 1974, now housed in the National Archives.

But salt can play a crucial role. Arnold is quick to point out that you should only add a very tiny amount—”we are not talking about salting the rim of your glass here!” he told Gastropod.

Arnold’s insight draws on the same logic that calls for adding a pinch of salt to most baked goods, from ice cream to pastry. “These very, very small quantities of salt really just cause all the flavors to kind of pop,” Arnold explains, because of the way our taste buds work.

Recent research has begun to tease out how the receptor cells on our tongues responds to sour, bitter, sweet, and salty tastes differently depending on their concentration and how they are combined. For example, if you add a tiny sour note to a bitter-flavored drink, it will actually boost the bitter sensation, but at a more moderate concentration, sour tastes suppress bitterness. (Try this at home, by adding a drop of lime to a margarita, versus the full ounce.)

Similarly, at very low concentrations, salt doesn’t register as a taste at all, but instead reduces bitterness and boosts sweet and sour notes in the food or drink you add it to. Basically, says Arnold, “next time you make a cocktail, add a tiny little pinch of salt to it and stir—and then tell me you don’t like it better.”

The 007 Question: Shaken or Stirred?

James Bond is famous—some might say notorious—for preferring his martini shaken, not stirred. But science-minded bartenders would urge you not to follow his lead—though Dave Arnold is quick to point out that the right way to make a drink is the way it tastes good to you.

Still, there’s some solid science behind why a martini should be stirred and a daiquiri shaken, rather than the other way around. Both methods chill, dilute, and blend your drink—but they have different effects on flavor and texture that work better with some cocktail recipes than others.

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Stirred rather than shaken for Gastropod, please.

Typically, Arnold explains, when you shake a drink, it will get colder—and thus more diluted—than it would be after stirring. “Banging ice rapidly around inside a shaking tin is the most turbulent, efficient, and effective manual chilling/dilution technique we drink makers use,” he explains. Because flavor perception, and sweetness, in particular, is blunted at cooler temperatures, a shaken drink needs to start out significantly sweeter than its stirred equivalent.

Shaking also adds texture to a drink, in the form of lots of tiny air bubbles. That’s a good thing when you’re making a cocktail with ingredients that taste nice when they’re foamy, like egg whites, dairy, and even fruit juice, and not as good when you’re mixing straight liquor with bitters. Sorry, Mr. Bond.

The other thing to bear in mind is that you really shouldn’t linger over a shaken drink. “The minute that someone hands you a shaken drink, it is dying,” says Arnold. “I hate it when people don’t drink their shaken drink right away.” We can’t responsibly advise you to chug them, so we recommend making your shaken drinks small, so that you can polish them off before the bubbles burst.

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Cocktails photographed by Travis Huggert for Arnold’s Liquid Intelligence.

Boozewashing: the Ultimate At-Home Mixologist Nerd Trick
Ever since the first ice-cube was added to the original cocktail recipe of liquor, bitters, and sugar, mixologists have loved their bar gear. Ice-picks, mallets, swizzle sticks, shakers, strainers, and even red-hot pokers were all standard features of the nineteenth-century celebrity bartender’s toolkit.

Today, Dave Arnold has added rotary evaporators, iSi whippers, and liquid nitrogen to the mix, placing the most cutting-edge cocktails out of reach of the home mixologist.

But there is one super trendy, high-tech trick that you can try at home. It’s called “booze-washing,” and it makes use of protein to remove the astringency from a drink.

It actually has a historic basis—even Ben Franklin wrote down his own a recipe for milk punch that uses the casein protein in milk to strip out the phenolic compounds and turn a rough-around-the-edges brandy into a soft, round, soothing drink. But Dave Arnold came up with the idea when he was trying to make an alcoholic version of an Arnold Palmer, the delicious iced tea/lemonade mix.

“I knew that adding milk to tea makes it less astringent, which is why the Brits do it,” Arnold explained. “And then I wanted to get rid of the milk, because I didn’t want a milk tea, I wanted a tea tea.” So he added citric acid, which caused the milk to curdle, so he could separate it out in a centrifuge. “And only afterwards was I like, oh yeah, milk punch!”

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Arnold demonstrates booze-washing in a sequence of photos from his new book, Liquid Intelligence. Photos by Travis Huggert, who is also responsible for the image used in the embedded Soundcloud player.

Arnold washes drinks to remove flavors, rather than add them. He’s taking advantage of the chemical properties of protein-rich ingredients—milk, eggs, or even blood—that preferentially bind to the plant defense chemicals that can give over-oaked whiskey, certain red wines, tea, coffee, and some apple varieties a mouth-puckering dryness. He’s found that as well as smoothing out a drink, booze-washing has the side benefit of creating a lovely, velvety texture.

The good news is that you don’t need a centrifuge to make the perfect milk punch or alcoholic Arnold Palmer at home. You can follow Arnold’s recipe (which he shares on the Gastropod website), let it sit overnight, and then strain out the curds through a cloth and then through a coffee filter.

According to Arnold, your yield will be a little lower than with a centrifuge, but the result will be just as tasty. His only word of warning is that you have to drink the resulting cocktail within a week, or else the proteins will clump together and the drink will lose its foaming power. But that shouldn’t be too difficult…

Listen to Gastropod’s Cocktail Hour for much more cocktail science and history, including an introduction to the world’s first celebrity bartender, an unexpected use for Korean bibimbap bowls, and a cocktail personality test based on Jungian analytics.

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The Twenty-Four Hour Loaf

In the opening episode of the BBC’s new three-part series, “Inside the Factory: How Our Favourite Foods Are Made,” we spend an hour watching a loaf of supermarket sliced white get made.

There is a short diversion into the history of bread-making (including Victorian-era DIY tests for alum adulteration) and a brief interlude in an oak forest to sample some wild yeast, but the star of the show is the factory itself: the mesmerising, balletic, perpetual motion machine installed beneath Allied Bakeries’ unpromising, West Bromwich-based, hangar-style shed.

First, the ingredients are rounded up. There is a stock shot of a combine harvester at work, but the real action takes place at the flour mill and yeast bioreactor. At Coronet Mill in Manchester, kernels of wheat loop through six miles of pipe, from mill to sieve, to mill to sieve, and around again, until they are reduced to dust.

6 miles of pipe

IMAGE: Six miles of pipe transport whole kernels, milled wheat, and flour around the ten-storey mill. Screen grab from the BBC.

The sieves themselves look like a series of self-storage lockers mounted on a seismic shake table. Rows of off-white boxes punctuated at regular intervals with green doors wiggle and bounce, twenty-four hours a day, seven days a week.


IMAGE: Sieves. Screen grab from the BBC.

Meanwhile, in Suffolk, six gigantic bioreactors turn 0.1 gram of yeast into 30,000 kilos (enough for 1.2 million loaves of bread) in just four days, before spraying, squeezing, and dehydrating it.

Yeast Factory bioreactors

IMAGE: The yeast factory’s bioreactors. Screen grab from the BBC.


IMAGE: Extruded and dried bakers’ yeast. Screen grab from the BBC.

Tankers bring the highly combustible flour, living yeast, and a variety of other emulsifiers and additives to West Bromwich, and then the supermarket loaf’s twenty-four hour journey from flour to shelf begins.

Only three and a half hours of that are required to knead, proof, bake, slice, and bag the bread; the rest is allocated to sorting, loading, and delivery. During that three and a half hours, the bread never stops moving.

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IMAGE: Dough balls “rest” for thirty-seconds for the gluten to form. Screen grab from the BBC.

Even the thirty-second “relaxation” period required between kneading and proving the dough takes place on a series of otherwise unnecessary conveyor belt loops. This is building as circulation: a gluten-based Epcot ride and mesmerizing Chris Burden installation rolled into one.

Ferris Wheel Proving

IMAGE: Proving dough. Screen grab from the BBC.

While a giant ferris wheel takes the loaves for a spin, muffins are funneled down Carsten Höller-worthy slides and into a series of race-track start gates.

Muffin slides

IMAGE: The slide slows and separates the muffins for the quality control inspector. Screen grab from the BBC.

Muffin racing

IMAGE: On your marks: the muffins head out onto the packaging track. Screen grab from the BBC.

Thus far, the process at least resembles a mechanical interpretation of home bread-baking, albeit using double the ingredients and a fraction of the time. But there is a secret to supermarket bread’s combination of squishiness and spreadability: a deft series of moves that rolls up the dough ball like a cigar, cuts it into four, and then squeezes it back together again in the tin.

1 Roll up

IMAGE: The bread dough is rolled like a cigar. Screen grab from the BBC.

2 Slice

IMAGE: This machine then slices and folds it in two, and then in two again, before funneling it back together. Screen grab from the BBC.

4 Four-way

IMAGE: The four dough cylinders, lined up so that their grain alternates. Screen grab from the BBC.

5 In tin

IMAGE: And then dropped in the tin, to reform into a single loaf. Screen grab from the BBC.

As the bread proves and bakes, the four cylinders become one again—but, because the grain of the dough flows in alternating directions, the resulting loaf is much less likely to tear under your butter knife.

6 Structure

IMAGE: The loaf on the left was not divided into four; the loaf on the right was. Screen grab from the BBC.

After a trip through the room-sized oven, the bread must be cooled to below 30°C, in order to be sliced and bagged. This is “the one bit of the process we can’t speed up,” Allied Bakeries’ manager complains. Over the course of two hours, the loaves slowly circulate up to the top of a multi-storey fridge and then wind their way down the other side.

Spiral looking up

IMAGE: Spiraling up the cooling tower. Screen grab from the BBC.

2 spirals

IMAGE: Two spirals in the cooling tower. Screen grab from the BBC.

After a trip through the slicer*, an ingenious blow-and-scoop motion inflates a plastic bag in time to catch the loaf as it falls from one conveyor belt to another.


IMAGE: Bagging the bread. Screen grab from the BBC.

And, with a final pass through the metal detector, the loaf’s journey grinds to a temporary halt. At some point in the next twenty hours, supermarket orders will come in, and pickers will load it onto a pallet, and then a lorry. From there, it goes from supermarket shelf to basket, to stomach—or, as the show’s presenters pointed out, the bin. (British shoppers throw away the equivalent of one out of every three loaves purchased.)

The episode is still available on iPlayer, as are the subsequent programmes in the series, on milk and chocolate. It’s the kind of food television I love—and that is vanishingly rare. Although the presenters point out the differences between industrial processes and home baking and the unnecessary nature of much food waste, there is no agenda other than curiosity. Most of us—even those of us that write and think about food almost constantly, like me—will never have seen the inside of commercial bakery, let alone the yeast bioreactors and flour mills that feed it. And it is a fascinating, awe-inspiring, and occasionally revelatory sight.

*As designer and food historian Cory Bernat once pointed out, sliced bread wasn’t really the greatest thing until cellophane came along to keep it fresh. Although Iowan Otto Rohwedder designed his “single-step bread slicing machine” in the 1920s, when the first pre-sliced loaf was sold on July 7, 1928, it was wrapped in wax paper, which was far from air-tight, as well as difficult to reseal. Fortunately, DuPont came out with the first impermeable plastic wrapping in 1927, and by the early 1930s, sliced bread was being sold in cellophane. “Cellophane on bread! Impossible, one might say, but it’s a fact,” reported the Sarasota Herald-Tribune in 1934.

For another look at food manufacturing’s industrial sublime, see “In the Time of Full Mechanisation.”

Thanks for the tip, Mum!

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Improbable Salt

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The illicit thrill of carrying vials of expensive white powder around town is just part of the charm of owning your own Improbable Salt.

I am no salt expert (yes, there is such a profession: meet salt sommelier Sommai Wooniem) but, astonishingly, the salt from a Hawaiian-French improbable ocean tastes distinctly different to that of a French-Hawaiian one.

(To my mind, French water mixed with Hawaiian sea salt has a slightly unpleasant, bitter, and metallic after-taste, though its creator, Ryan Dewey, prefers it to its inverse twin. Give me Fijian-Pakistani salt over either, any day.)

Last chance to score your own vials of fourth-wave, post-globalisation, micro-batch salt, freshly harvested from the shelves of a Cleveland supermarket: Dewey’s Kickstarter campaign ends on Monday evening.

Thanks to Jenny, Jake, and Geoff for tasting the salts with me.

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Gastropod on Gastropods

Finally, Gastropod is tackling gastropods! In this episode, Cynthia visits one of America’s first and only snail farms.

Though Gastropod is, as regular listeners know, a podcast about the science and history of all things gastronomical, we do share a name with Gastropoda, the taxonomic class that includes slugs and snails. And, as it turns out, the history and science of heliciculture, or snail farming, is completely fascinating.

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IMAGE: Snail pen at Little Grey Farms escargotière, Quilcene, Washington. Photograph by Ric Brewer.

Join Cynthia on a trip to rural Washington State to learn how to raise snails and whether fresh and vacuum-packed taste any less rubbery than canned. Plus, you’ll hear about the earliest evidence for human snail consumption, how the Romans fattened theirs up, and all about the bizarre world of snail sex.

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IMAGE: Snails in Little Grey Farms’ Seattle warehouse. Photograph by Ric Brewer.

And, when you’ve listened, visit Gastropod for all kinds of links, photos, and even a snail orgy caught on home movie.

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Supply Chain Seasoning

Salt is essential. Globally, humans eat an average of 10 grams a day and we each contain roughly 250 grams, without which we would die.

Wisconsin French

IMAGE: Photograph courtesy Ryan Dewey.

As Mark Kurlansky explains in his book, Salt, the extraction of salt has inspired many of the world’s most ambitious public works projects, while the exchange of salt laid down many of the global trade routes still in use today.

As Kurlansky tells it, the Chinese developed an advanced system of urban plumbing inspired by their advances in salt-well bamboo pipework, the Romans built the first of their great roads, the Via Salaria, to bring salt into the interior of the Italian peninsula, and settlements all over the world—including Buffalo, New York—were situated at salt licks, to which convenient paths had already been blazed by animals (in that case, bison).

The salt at the end of the longest, most infrastructure-intensive supply chain in the world, however, is the salt from Improbable Oceans.

Artist and cognitive scientist Ryan Dewey is currently running a Kickstarter campaign to fund the production of what he describes as “the first true sea salt from oceans that don’t exist.” Its production process combines two elemental commodities that are shipped vast distances around the world only to be marketed based on their taste of place: mineral water and sea salt.

Improbable salt

IMAGE: Photograph courtesy Ryan Dewey.

The result is small-batch, hand-harvested salt that captures the taste of two places that could never overlap outside the totalising geography of the grocery store—salt evaporated from the Wyoming-French ocean, for example, or the New Zealand-Icelandic sea.

The project began with kitty litter. Dewey is principal of the Geologic Cognition Society, a collective he founded in 2013 to attempt to make geologic timescales and forces more legible to humans. The minerals in the kitty litter on the shelves in an average Walmart may well, Dewey realised, have been mined in Wyoming, travelled by train to California, sailed to China to be processed, returned back to California by sea, and then traversed half way across the country again, via a central distribution center, to your store.

With an estimated 74 to 96 million total cats in America, and each indoor cat using, on average, 60 pounds of kitty litter each year, this distributed sedimentary movement is actually, it seemed to Dewey, “a pretty radical form of geo-engineering.”

Core Samples

IMAGE: Photograph courtesy Ryan Dewey.

At first, Dewey began assembling core samples of the mobile minerals available at your average supermarket: kitty litter, activated charcoal, pumice, and, of course, salt. The core samples were a tool, he explained, to help visualise “these imagined spaces that exist at the convergence of supply chains and retail inventory.” But, while he was scanning the shelves, he realised that, between the gourmet salt selection and the aisle of mineral waters, the grocery store was home to hundreds of latent oceans, each of which could yield an as-yet-untasted salt.

With no particular effort, Dewey was able to assemble ten mineral winters from across the globe—Hawaii, New Zealand, Fiji, Iceland, Norway, Croatia, England, France, Wyoming, and Ohio—and ten salts from equally far afield: Hawaii, South Africa, Pakistan, California, Portugal, France, New Zealand, South Korea, Sweden, and New York.

This immediately gave him the ability to make one hundred different improbable oceans in his Cleveland lab, in which the trace minerals that give Fiji water its particular flavour mingle with, for example, the unique “merroir” of Hawaiian sea salt. The result, after steam-condensing the ocean into a brine and then evaporating off the remaining water, is a seasoning whose taste perfectly captures the geography-distorting anyplace of the global supply chain.


IMAGE: Photograph courtesy Ryan Dewey.

Dewey’s early experiments have revealed that salt from an ocean made from French mineral water and Hawaiian salt tastes distinctly different from the salt that crystallises when he evaporates a combination of Hawaiian mineral water and French sea salt. (He prefers the former.)


IMAGE: Photograph courtesy Ryan Dewey.

The most improbable ocean, ranked purely on the mileage required to bring its two ingredients together in Dewey’s Cleveland base, is formed by the combination of New Zealand water with Portuguese salt. Foodies eager to taste these varying degrees of improbability themselves can choose to order single 2-dram vials of the New Zealand-Portuguese salt, inverse salt pairs, or entire flights.

The experience does not come cheap—Dewey thinks that his salt is almost undoubtedly the most expensive in the world, which is only fitting when you consider the resource-intensive supply chain that lies behind each improbable ocean (not to mention the time-consuming process of evaporating each micro-batch by hand).

Alongside the production process, Dewey plans to continue his exploration of how global supply chains shift geology, collapse geography, and create new kinds of places—as well as the products that express them.

He is experimenting with ageing his oceans, in order to reintroduce some kind of temporal variability into his salts. And he is planning to expand his harvest to include oysters: perhaps, he hopes, ending up with bivalves that have adapted over multiple generations to the particular waters of an improbable ocean.

Meanwhile, Dewey is also starting to cast salt in his furnace, and, with the Geologic Cognition Society, will be reconstructing the ancient brinescape that formed the rich seam of rock salt under Lake Erie for an exhibit opening in Cleveland in January. (A surprisingly large proportion of U.S. road salt comes from a Cargill-operated mine that extends four square miles out from the shore of downtown Cleveland, 1,700 feet beneath the lake’s surface.)

Seaweed in ocean

IMAGE: Photograph courtesy Ryan Dewey.

Visit Dewey’s Kickstarter page for your chance to taste the ineffable, improbable flavours of global trade and anthropogenic geo-engineering.

This is salt that can only exist at this particular moment in planetary history—salt that the ancient Chinese and Romans, for all their infrastructural ingenuity, could never have imagined. It combines the abstract logic of capital with the artisanal craft of micro-local production in seasoning form. Its ridiculousness is precisely the point.

I cannot wait to try it.

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Gastropod: Savour Flavour

Why does grape candy taste so fake? What on earth is blue raspberry, anyway? And what is the difference between natural and artificial, at least when it comes to flavour?

Join us as we taste the rainbow on this episode of Gastropod, from artificial flavouring’s public debut at the 1851 Crystal Palace exhibition, to the vanilla-burping yeasts of the future. We’ll experiment with Skittles, discover how invented flavours first appeared in our daily diets, and visit a synthetic biology lab, all in our quest to understand what artificial flavour is, was, and might be. Along the way, we’ll learn what exactly goes into designing the perfect pineapple from one of America’s top flavourists, investigate beaver butts, and discover the taste of an extinct banana. Listen now!

Throughout human history, if you wanted to make a dish taste like strawberry, you had no choice but to add a strawberry. But in the 19th century, scientists began to understand how to synthesise flavour chemicals, whether from plants or from byproducts of coal processing, to evoke familiar flavours. While the technology to evaluate the flavour molecules of a particular food have become increasingly sophisticated in the past century, the basic concept of synthetic flavour has remained unchanged. Until now. In this episode of Gastropod, molecular biologists explain how they’re designing yeasts to ferment the tastes of the future.

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IMAGE: The Great Exhibition of 1851 was housed in Joseph Paxton’s extraordinary Crystal Palaces, and contained “the wonders of industry and manufacturing from around the modern world,” including folding pianos for yachtsmen, a couple of velocipedes (the early version of a bicycle), and, of course, some lozenges flavored with artificial fruit ethers.

Natural vs. Artificial

Let’s start with a graham cracker. Just like Sylvester Graham back in 1829, if you’re baking at home, you’d probably use coarse-ground whole-wheat flour, wheat bran, and wheat germ. These, along with some honey for sweetness, would give your graham crackers their distinctive toasty, malty, and slightly nutty flavor.

If you’re making them by the billion, however, at a Nabisco or Keebler factory, the ingredients list looks a little different. That extra wheat germ and bran contain natural oils with a tendency to go rancid—but, when you cut them out to gain shelf-life, you lose the flavour.

Fortunately, there’s an easy solution: you can add all that flavour back with just a touch of a light yellow, crystalline powder called 2-acetylpyrazine. This is an aromatic, carbon-based chemical, known by flavourists as the “graham-cracker” flavor. It occurs naturally in nuts and toasted grains; as the vital ingredient giving factory-made graham crackers their signature flavour, it can either be extracted from a plant or synthesised using petrochemical derivatives.

The major difference is that 2-acetylpyrazine produced by performing chemical reactions on plant matter costs about $25 per lb—compared to the $5 or $6 per lb it costs to produce the kind whose raw ingredients come in a drum.

However, using the cheap version comes with another, increasingly significant cost: it means you have to include the words “artificial flavour” on your graham cracker ingredients list. Under FDA rules, if the raw material to make your flavour chemical comes from a plant, animal, or edible yeast, it’s “natural,” for the purposes of labelling. If it comes from anything else, it’s artificial. And consumers increasingly don’t want to buy things that are “artificial.”

In fact, Michelle Hagen, a senior flavourist at Givaudan, the world’s largest fragrance and flavour company, told Gastropod that, despite the cost savings, she hasn’t used a single artificial chemical in her flavourings for the past four years—because the companies she mostly works with know that customers are turned off when they see that word on a label.

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Enter the (Genetically Engineered) Yeast

Until recently, the natural flavours that Hagen uses would, for the most part, have been extracted from a plant; a handful of rarer ingredients, more often used in perfumery, would have come from animal sources. Today, advances in genetic engineering, combined with the growing consumer demand for natural flavours, are creating an intriguing new option for the world’s flavourists. In the past, the mention of “edible yeast” in the FDA definition of natural flavours typically referred to savoury yeast extracts; now, designer yeasts are beginning to pump out vanilla, saffron, and even grapefruit flavours.

For this episode, Gastropod visited Ginkgo BioWorks, one of a new wave of companies redesigning yeasts to produce fragrance and flavour chemicals. As Christina Agapakis, a scientist, writer, and artist who recently joined Ginkgo’s staff, explained, the biology behind genetically modifying microbes to produce other, useful chemicals is not new. More than three decades ago, in 1978, biotech companies successfully inserted genes into bacteria to produce human insulin, meaning that diabetics need no longer depend on a close-enough version extracted from pig pancreases. In 1990, the FDA approved rennet made by inserting cow genes into E. coli bacteria; today, more than 90 percent of all cheese in the U.S. and U.K. is made using this bio-engineered product, rather than natural rennet found in the stomach linings of calves.

What is new, Agapakis told Gastropod, is “the ability to create flavors.” Rather than inserting the single gene that codes for the insulin protein, she explained, “to make a flavour, you might need five or ten different enzymes that are creating a whole pathway and are really shifting the metabolism of the yeast.” Fitting all those genes together so that what works in a plant to produce flavour also works in a yeast cell is challenging. Ginkgo has been developing its first yeast-fermented ingredient—a rose oil for the fragrance industry—for a couple of years now.

In fact, as organism designer Patrick Boyle explained, the main reason that the Ginkgo “foundry” is filled with liquid-handling robots and high-tech machines is to help him and his colleagues rapidly run through all the tweaked yeasts that don’t work. “Failure is usually not very dramatic,” he told Gastropod. “It’s just that we end up with a yeast that looks a lot like the yeast we started with.”

Still, a Swiss company called Evolva has recently brought the first of these “cultured flavours” to market: vanillin, the main ingredient in the world’s most popular flavour. Ginkgo’s rose oil smells pretty sweet, and the Boston-based company has half a dozen more flavour ingredients in the pipeline. And scientists in Austria just announced that they have successfully tweaked yeast to produce the key flavour chemical in grapefruit.


IMAGE: Photo courtesy Ginkgo BioWorks.

The Future of Flavor

Redesigning yeast to create flavour molecules offers some potential benefits. For starters, fermentation requires none of the harsh chemicals that are often used to extract essential oils from plants or react with petrochemical precursors. Engineered yeast also offers the possibility of democratising rare, expensive flavours, like saffron, and, Patrick Boyle points out, it can “relieve some of the supply issues that come from using really rare plants.”

But the main attraction of this new technology for food companies is that the resulting flavours can legally be labelled as “natural”—they are produced by a yeast, after all. What’s more, because there is no yeast left in the final product, cultured flavours actually don’t contain genetically modified organisms.

Still, companies are nervous—Michelle Hagen at Givaudan told Gastropod that she hadn’t worked with any of these cultured flavours yet, and both Nestlé and General Mills responded to pressure from Friends of the Earth by pledging not to use cultured vanillin. In a press release, Friends of the Earth argued that using yeast to produce vanillin would threaten the livelihood of vanilla bean farmers in Madagascar, as well as the continued existence of the rainforest in which the vanilla orchid grows. But, as Patrick Boyle pointed out, the world demand for vanillin far outstrips the quantity of vanilla beans grown each year, and the synthetic and real vanilla industries have already managed to co-exist for more than a century.

Debates over natural vs. artificial aside, perhaps the most interesting aspect of these designer yeasts is the potential they offer for creating entirely new flavour experiences. For Christina Agapakis, the opportunity to learn more about the genes and pathways that plants use to express flavour will, she hopes, lead to productive collaborations with fruit and vegetable breeders—and increased deliciousness in the field as well as in the lab.

Meanwhile, while the Jurassic Park-style idea of recreating extinct species from some DNA trapped in amber is still a fantasy, Agapakis speculated that it might be possible to work with evolutionary biologists to reconstruct the genetics of lost plants from their living relatives. One day, designer yeast could allow us to get close to the flavour of extinct or endangered species, or even pre-domestication grasses and animals.

To end where we began: forget whether your graham cracker uses natural or artificial flavours. Instead, imagine a series of crackers whose flavours progress through wheat’s evolutionary history. Then listen to this episode of Gastropod to understand how the flavour industry got started, and what its evolution can tell us about our relationship with food.

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