This is a transcript of the Gastropod episode Cutting the Mustard, first released on February 27, 2018. It is provided as a courtesy and may contain errors.

ROSE EVELETH: So I’m Rose Eveleth. I’m the host of Flash Forward, which is a podcast about the future. But more importantly I am a very huge fan of mustard.

CYNTHIA GRABER: And you and I were actually talking about this, I don’t know, a year or two ago, and you were, like, you have to do an episode on mustard! So why are you obsessed with mustard?

EVELETH: So it’s funny—in thinking about this call we were going to have, I figured you would ask me that question and I realized that I don’t have a great answer. I mean it is objectively the best condiment. But that’s not the best answer. I mean it’s just really delicious, it goes on everything. But I wanted you all to do an episode on it because I am a fan of mustard and I consume a very large quantity of mustard, probably an embarrassing amount of mustard, but I don’t actually know that much about how mustard is made. Like, I’m familiar that there is a mustard plant and a mustard seed. But what actually makes different mustards different is actually sort of a mystery to me. I just eat them. I don’t know that much about them.

NICOLA TWILLEY: That’s what we’re here for, is to do the Googling that you can’t be bothered to do.

EVELETH: Exactly. I’m too lazy, I need an episode of Gastropod.

TWILLEY: Fortunately, Cynthia and I are not lazy at all ever in any way.

GRABER: I hope everyone believes you.

TWILLEY: And so Rose’s wish was our command. I’m Nicola Twilley.

GRABER: And I’m Cynthia Graber, and, as Rose pointed out, this is indeed an episode of Gastropod, the podcast that looks at food through the lens of science and history. We are happy to look into mustard, but Rose, in return you have to answer all my questions about what life might be like in the future. But first, mustard, what do you want to know?

EVELETH: I guess, you know, I eat a lot of mustard and I know a lot about the different kinds of mustard that I could purchase on the market, right? I know the, you know, various varieties of consumer goods related to mustard. I know a lot about how mustard tastes. I know nothing about the pre-going into my mouth parts of mustard. I mean I get the basics—there is a seed. You know, it’s like it’s in many ways like a lot of other things that are made from seeds. The powder seems obvious to me, right? It’s like ground-up seeds. Maybe I’m wrong about that. Who knows? You know, actually.

TWILLEY: Side note, which we didn’t say because we didn’t want to puncture Rose’s belief in all things Gastropod, but we didn’t actually know. Then. Now we do!

(PRE-ROLL)

(MUSIC)

GRABER: Rose has been a mustard fan for a long time.

EVELETH: I used to be an athlete in, like, high school. And so I was constantly at various athletic events and they often would sell pretzels and hot dogs and stuff like that. And I think that was when I realized that mustard is far superior to ketchup. And so I was always really into mustard. But I don’t actually know that much about, like, what the process is to take a mustard plant, and if there are, like, multiple different kinds of mustard plants, and that’s how we get these various different kinds of mustard. Like what makes Dijon, Dijon? Is it the plant, is it the seed, is it the processing? Is it some combination of all of those things? And so I was just curious about what where mustard comes from and sort of how all of these different types of mustard are made.

TWILLEY: So many questions! So many answers! But let’s start by getting our basics down: what exactly is this mustard plant of which Rose speaks?

PATRICK EDGER: So the mustard family actually consists of about 3,600 different species and so there’s quite a bit of diversity. Most of the species are the types that you would see growing in the cracks of sidewalks.

GRABER: Patrick Edger is assistant professor of horticulture at Michigan State University.

EDGER: The mustard family really consists of, you know, lots of wild species, but most notably the majority of the vegetable crops that you probably eat and consume every day. You know: broccoli, cauliflower, Brussels sprouts, kale, radishes, as well as like wasabi as a condiment or mustard as a condiment. But in addition there’s a lot of oil-seed types. So we would have things such as, like, rapeseed or canola oil that we would cook with. Those are all from the very same family.

TWILLEY: Fortunately, for the sake of my sanity, the kind of mustard that we can buy in the store labeled as mustard only comes from three plants within this enormous family: black mustard, brown mustard, and white mustard. Confusingly, the white seeds make yellow mustard, and the brown seeds are a kind of beigey-yellow inside, so the whole color terminology is not particularly helpful. But all three kinds of mustard seed have one thing in common: they’re tiny.

GRABER: And this is just the point of another mustard story Rose told us.

EVELETH: Yeah, so my grandparents on my mom’s side are Catholic and when I was a kid my grandma gave me this charm bracelet. And it had all sorts of various Catholic charms on it, it had obviously a little cross but it also had a bunch of other little charms that were relevant to various parts of the Bible or stories or whatever it was. And I was a very, like, tomboy kind of kid so I was, like, I’m not going to wear jewelry, this is stupid. But there was one charm on the bracelet that I was really into because it was this tiny little magnifying glass that you could flip open and you could look into it. And it just magnified one mustard seed. And I guess this comes from a parable of the mustard seed in the Bible.

GRABER: I had never heard of this parable of the mustard seed before—probably because I’m not too familiar with the New Testament.

TWILLEY: Whereas I had, despite never consciously listening in church at school.

CLIP OF MAN READING FROM THE BIBLE

EVELETH: Yeah, so I should say that I’m not a scholar of the Bible and nor am I a believer. So, like, I’m not an expert here. But it’s basically about how the mustard plant is really large—they can get to be nine feet tall. And for a plant that big they have small seeds. And so the story, the parable in the Bible, is kind of about that size difference—that when that tiny, tiny seed is planted in the earth it makes a giant plant. It’s kind of one of those “don’t judge a book by its cover,” I think, ideas—that even though the seed is so small it can become this great huge beautiful thing with birds and, you know, branches and all this stuff. So that’s kind of, I think, what the parable is about—if I’m interpreting it correctly, which I could be not doing.

TWILLEY: I am not a believer or a Biblical scholar either, but, from the best I can tell, this mustard seed story is actually more about how the kingdom of God will grow from its tiny beginnings.

GRABER: Which I still don’t really get, but that’s fine. It’s not meant for me.

TWILLEY: But this Jesus connection has an interesting side note attached to it. Supposedly because Christians were so attached to their mustard seeds, they carried them with them and scattered them as they walked, and so mustard plants grew along their trails. One of the places you hear about this happening is in California. People say that one of the early missionaries, Junipero Serra, walked north from the San Diego mission in the 1700s, scattering mustard seeds as he went. And the resulting quote “Bible trail” is apparently still marked by mustard plants today.  People say the same thing about pilgrim routes on the east coast of the U.S. too. You’re supposed to be able to see them clearly from above, thanks to their bright yellow flowers.

GRABER: There’s a Gastropod fan and supporter who happens to—okay—be a friend of yours Nicky, AND he also happens to work for a company that specializes in satellite mapping. So we figured, maybe he’d know if this supposed mustard trail is indeed visible from space. Do the satellite images show the particular visible signature of mustard?

TWILLEY: So my friend Wayne does actually have a real job, so he could not devote too much time to the search, but he told us that unfortunately, most purchasers of satellite imagery actually want something called “leaf-off images”—these are images captured in the winter where there isn’t a ton of foliage covering up all the other features they’re interested in. So, long story short, no luck.

GRABER: If anyone knows whether this California mustard trail tale has been proven true or false, please get in touch!

TWILLEY: But Rose doesn’t love mustard for its religious connections. She loves it because of its heat—its pungency and flavor.

EDGER: That sharp, pungent, bitter flavor that we sense are from compounds called glucosinolates. There are roughly a hundred and twenty-some different compounds and depending on the abundance and the profile of, like, the composition of these various compounds, that’s what gives cruciferous vegetables that sort of flavor.

GRABER: Now remember, these cruciferous vegetables—there are a lot of them: kale and Brussels sprouts and broccoli, just to name a few of my favorites. They have some of these glucosinolates—maybe slightly different ones with slightly different flavors. But things like kale and cabbage don’t have nearly as much pungency as mustard does.

TWILLEY: In other words, there’s a whole spectrum of spiciness between species, depending on which and how much of those 120 different glucosinolates they have.

GRABER: But here’s a question: What purpose does this pungency have for the plant?

EDGER: Yeah, so like most organisms plants do not want to be predated on. They don’t want to be consumed. And being a plant when you’re fixed in a location and you’re constantly combating insects and fungal pathogens and bacteria and viruses, you have to have some way to defend yourself. And so most of the flavors or things that we describe as flavors are actually chemical compounds that plants used to ward off being predated upon. And glucosinolates are one of those examples.

TWILLEY: Unsurprisingly, there’s an evolutionary reason for why the seeds of a mustard plant—the part we use for making the condiment—are much spicier than its leaves, which we use in a salad.

EDGER: If the purpose of a plant is to pass on their genetic material, they will invest quite a bit of that into their seeds to protect actually that next generation. So in mustard seeds, there’s lots of glucosinolates.

GRABER: These glucosinolates are really poisonous to some species—they kill insects.

EDGER: Glucosinolates are actually incredibly toxic even to the plant. The plants will actually sequester a lot of the precursor molecules in vacuoles that safeguard it even from the cell. So that’s how toxic they are.

GRABER: Those special containers get broken open when an insect starts chomping.

TWILLEY: But here’s where these mustard toxins gets even more interesting. A couple of years ago, Patrick published a paper tracing what he calls the great butterfly-mustard arms race. The story starts 90 million years ago, when the first mustard plant ancestors figured out how to stop caterpillars from eating them—by producing some glucosinolates.

EDGER: When the compounds first evolved, it would have been an instant barrier for predation, right? And so that actually would have permitted that ancestral plant that just evolved this novel trait to diversify very rapidly across the landscape. Because now it basically has a wonderful sort of set of armor for any predation to occur.

GRABER: So now the mustard great-great-great-etc. grandparent is super chill. The caterpillar can’t eat it, it’s free to grow and spread across the landscape. For at least a few million years.

TWILLEY: But the caterpillars aren’t done. They are hungry, hungry caterpillars.

EDGER: So the insects evolved a enzyme, a novel enzyme, a brand new gene, that actually, as the insect is consuming these glucosinolates, actually cleaves the compounds—this chemical compound—to make it an inert structure.

GRABER: So now these glucosinolates are no longer toxic to the caterpillars, and now the caterpillars are the happy ones.

EDGER: We then see, as one would predict, it now has a buffet.

GRABER: They can eat as much as they want of this spicy plant that no other insect can snack on.

TWILLEY: And now it’s the caterpillar’s turn to spread and diversify and generally be boss. But, as you would expect, the mustard plant ancestor does not take this lying down. Like Patrick said, it’s an arms race.

EDGER: We actually see repeated cycles of this—minimally, three of them that have occurred over the last 90 million years.

GRABER: This is plant-animal warfare, people. For his experiment, Patrick and his colleagues studied hundreds of species of related plants—plants that trace their ancestry back to those original, millions-of-years-ago genetic splits. This way they could figure out the timeline of when each side temporarily was victorious.

TWILLEY: They could see these big leaps forward in mustard defenses written in the plants’ DNA. One thing to know: lots of plants pass multiple copies of their genomes down to their offspring, instead of the single copies that we humans pass on to our kids. And this extra genetic material gives the mustard plants so many options to play with—so many different pathways to make new, improved glucosinolates.

EDGER: After every set of duplications, you basically would have a new and fancier set of defenses. And this escalated over time until the present day where many of the mustard plants have, you know, over 100 compounds in them.

GRABER: Here’s one of my favorite points in this whole research: this arms race led to amazing success for both insects and plants. As the war went on, it actually created many, many new species of both brassica and butterflies. Both dramatically increased in biodiversity and habitat. It is at least partly due to this arms race that we have kale and collards and cauliflower and Brussels sprouts and horseradish and radishes and mustard and everything.

EDGER: As the brassicaceae were more successful, that actually permitted subsequently the butterflies to be more successful. But then they also each of them have shaped the underlying genomes or even the phenotypes of one another. Ultimately, we really have the butterflies to thank for mustards, right? Mustard compounds. None of this would have existed if it wasn’t for this arms race.

TWILLEY: Next time you squirt mustard on a hot dog, remember to thank a caterpillar. So that’s cool, but my favorite part of Patrick’s experiment is that as part of his whole process, he found plants that are living today that have the level of glucosinolates that mustard used to have in the past.

EDGER: There are actually relatives from those ancestral intermediates that you can go out and you could potentially sample. And that was part of the study. We found all these sort of intermediate lineages—remnants. And from that, we can actually make estimates of what those profiles probably were like. We can’t be very definitive about it but we can make really pretty solid estimates of what those ancestral states would have been like, going back to at least 90 million years.

TWILLEY: I temporarily lost my mind for a minute when I heard this and decided that what Cynthia and I needed to do was track down all these milder-tasting relatives and do a mustard tasting through evolution, from bland to fiery.

GRABER: That sounds awesome, of course, but then you realized that it’s just the two of us and we have to put out shows and that would take months of plant collection and seed crushing.

TWILLEY: But if some millionaire mustard-ophile out there would like to fund this quest, I am available to talk offline. The 90-million year mustard tasting awaits!

GRABER: And I will happily join in. So Patrick and his colleagues wrote about this butterfly-mustard arms race. But here’s something that might scare you: the battle is not yet over!

EDGER: We see this constantly happening. So a lot of cabbage butterflies, if you grow any cruciferous vegetables in your backyard—broccoli or cabbages or cauliflower or what have it—you’ll see lots of cabbage butterflies always trying to predate on it.

TWILLEY: And that means that the plants need to be upping their game. And they will.

EDGER: I could imagine a mustard being spicier.

TWILLEY: Not just spicier, but even with a slightly different flavor profile, from new variations and combinations of these glucosinolates. Basically, we can’t even imagine the mustards of the future!

GRABER: Rose, this is the episode you get to make!

TWILLEY: Right, you do mustards of the future, we do the mustard science, and, next, mustard history.

(MID-ROLL)

HAYLEY SAUL: At this stage, I would say that these findings are the earliest conclusive use of spice for a culinary purpose.

GRABER: Hayley Saul is an archaeologist at Western Sydney University. And, a few years ago, she and her colleagues discovered the earliest known example of spiced food in human history—dishes perked up with, yes, mustard.

TWILLEY: OK, picture the scene. It’s more than 6,000 years ago, and you are in northern Europe, eating a plant called garlic mustard.

SAUL: So there were three main sites where we found the evidence of garlic mustard. One of them in Germany, which is a site called Neustadt, which is actually now underwater. It’s been excavated underwater. That inundation is actually one of the reasons why the pottery and the pottery residues are very well preserved because the waterlogging is great for preservation. And the sites in Denmark—so the sites are called Åkonge and Stenø,and they’re located on the edge of a bog.

GRABER: There are a lot of sites like these found near water, because water is a great source of food. But the people who were living at these sites, were they just hunting and gathering all the wild plants and animals that lived in and near the water? Who were these people?

SAUL: So, you know, all of the sites actually span the sort of Mesolithic/Neolithic transition, which is the time at which people were starting to just domesticate and experiment with domesticated plants and animals. So the people that lived kind of in the Mesolithic tend to be associated with hunting and gathering. But it’s actually much more complicated than that, really. It wasn’t the case that people just gave up on hunted and gathered foods and then adopted these new, more superior types of domesticated foods. They were actually combining things and it was just a period—I like to think of it as a period that was very creative. And there were new types of food coming in but people were starting to sort of explore how they can combine it with food that they’d used for years.

TWILLEY: What Hayley’s saying is surprising to me. I don’t tend to think of Mesolithic or Neolithic people as being culinary wizards or experimenting with their food to create new textures and flavors.

SAUL: I think there’s been a kind of an assumption in general that in prehistory, people were driven by just the need to get a certain amount of energy and that there was nothing particularly artistic about food practices in prehistory. And in part that’s brought about just because of the techniques that we have and the difficulty of finding certain evidence. So it’s quite easy to document animal bones on a site and slightly more difficult to document plants because they don’t preserve very well.

GRABER: In the past, scientists have been able to figure out what people were eating on a kind of more general scale—did they get more of their calories from protein or from fat, did they go fishing, or were they butchering domesticated cattle? But, until recently, it’s been much more difficult to get a fine-grained look at the flavors of the foods prehistoric peoples were cooking. But now, there are new techniques that Haley says can give a higher resolution look at ancient diets.

TWILLEY: These higher resolution techniques include starch analysis, as well as drilling into food residue to analyze the fats. There’s also a kind of microscopic analysis to match the tiny fossil remnants of plant cells, which are called phytoliths, to a catalog of different plant species collected from the area. The combination of all these techniques, plus how well preserved the food residues were at these sites, meant that Hayley and her colleagues were able to get that more nuanced and detailed picture of what these early northern Europeans were eating.

GRABER: And there was a lot of food residue for Hayley and her colleagues to analyze.

SAUL: In some cases it was up to a centimeter thick, because the pottery wasn’t necessarily cleaned. So it was just becoming more and more carbonized, and thicker and thicker residues. A bit like you would use a skillet, the flavor is partly brought to the food because the skillet is sort of reused again and again and again. And it’s only when the carbonization of that residue becomes so distasteful that the pottery is actually thrown away into the lake or into the sea. And at that point, it’s just like a record of reuse and a kind of build-up of all of these different meals that the pots been used for.

GRABER: And Haley’s big find from this food residue? These Mesolithic people were revving up their stews with a plant called garlic mustard. I know I said this already, but—drumroll!—this is the earliest known culinary use of a spice in the world.

SAUL: It’s from the seed husk, the actual sort of hardened shell of the seed, which has a flavor, if you grind it up, much like mustard.

TWILLEY: Hayley was able to figure this out by comparing the phytoliths—these plant micro-fossils—to the microscopic structures you find in garlic mustard today.

SAUL: I had to do a lot of just going out into the countryside and foraging for plants that were edible and, you know, making up the reference collections and things. And it’s one of those plants that you could so easily overlook. It’s just everywhere. And once you get your eye in you can see that it’s everywhere. It’s a plant that’s available across the whole of Europe, right into India and parts of Asia as well. But it’s not just usable for the seeds. The leaves of the plants are edible as well. The reason it’s called garlic mustard is because the leaves have a very garlicky aroma but the seeds have a very mustardy flavour. So you can sort of combine two different flavors in one plant really.

GRABER: That sounds delicious. But we were wondering—maybe garlic mustard was a major source of calories for the folks in these settlements. How can we know it was being used intentionally to flavor their food?

SAUL: The seed itself of Alliaria petiolata is very small and it’s woody. Some people have suggested that it has properties for preservation. It may have medicinal properties. But, because it’s so woody, in terms of delivering anything like energy or a great deal of vitamin nutritional value, it doesn’t really do that. So it seems to be much more that it’s being used at least in part because of its aromatic properties. So it is imparting flavors into the food.

TWILLEY: Basically, it turns out that Hayley is pretty confident that Mesolithic people had Rose Eveleth-style levels of enthusiasm for mustard. They too thought that there was nothing that didn’t taste better with some mustard!

SAUL: So we were finding from the lipid residue analysis that they were combining garlic mustard with marine fish.

GRABER: They also made stews of garlic mustard and meat from animals they either hunted or raised, like cattle or deer.

SAUL: It’s such a common spice it’s almost like they’re using it as we would use salt and pepper. And that suggests to me that it could have an even longer history. But we just don’t know at this stage.

GRABER: And actually, there are even older sites around the Mediterranean that have plant remains from other spices and herbs—poppy, cumin, and coriander—but the plant bits are not embedded in cookware. So we can’t be positive that people were actually eating these spices. But maybe they were.

TWILLEY: Really, though, the important question here is, what did these mustard-spiced dishes taste like? Fortunately, Hayley can answer that one too.

SAUL: Because my research involves me sort of going out and foraging for plants for my reference collection, the temptation is always there to try out what the flavors of those different plants were, yeah, so I have made some unusual concoctions of my own. But if you can find some garlic mustard, just grinding it up in a pestle and mortar and you can smell the mustardy flavor as you’re grinding it as well. And it’s delicious in a nice stew.

TWILLEY: Yes, that’s right: Hayley made her own Mesolithic garlic mustard stew.

SAUL: I used it with some venison. My dad’s a butcher, so I managed to get a nice cut of venison.

TWILLEY: And?

SAUL: It did taste quite contemporary. It’s not such a strong flavor as the sort of mustard that you would get in a pot. But there is definitely a sort of flavor of mustard.

GRABER: I love the idea that the earliest known use of spice involves garlic mustard. Two delicious flavors in one plant. But, for Hayley, even more importantly, this finding helps us rewrite the stories we tell about the people who were alive back then.

SAUL: It’s easy to fall back on the idea that people were sort of caveman-like and, you know, they were just out to sort of eat as much and as often as they could because they never knew when their next meal was, and things. But actually I would say that they were extremely sophisticated, and they had such sophisticated skills at acquiring food that they could sort of be really creative about the ways that they were combining foods.

TWILLEY: This is another thing that Rose and our Mesolithic friends have in common: mad mustard-pairing skills.

EVELETH: I put it on everything. I mean, I’m a big carb person. So, like, any kind of bread product, it’s good on. Olive bread with mustard is extremely delicious. I mean, obviously there are pretzels, but you can also put mustard powder on things like popcorn. So, like, a little bit of soy sauce and mustard powder on popcorn is delicious.

GRABER: I’d love to try that popcorn. But so I was wondering, you know, can you walk us over to your fridge? Tell us about how many jars you have and could you list some of the ones that you see?

EVELETH: Yeah. All right, I will—I’ll take you over. Hopefully my dog doesn’t get too interested in what we’re about to do. Okay, I’m opening the fridge. Let’s see, where are we. So there’s this great mustard place called—I’m going to mispronounce it. Maille? Maille? M A I L L E. Okay, so we have a bunch of those. I have a walnut mustard from them. I have a Dijon blackcurrant liqueur mustard from them, which is really good. It’s like—it tastes like Thanksgiving. It’s amazing. Really good on French fries actually, because, like, they’re sort of a good vehicle for any kind of mustard but they taste like Thanksgiving French fries. I have a blue cheese mustard which is super strong. You kind of have to, like, be a little gentle with this one. We also have an amber ale honey mustard from this farm up in Vermont that is near a place where we go skiing every year. We, of course, have sort of the standard spicy brown for sort of hotdogs and all that stuff.

TWILLEY: There’s more—many more jars. The thing is, it’s not just Rose that’s crazy about mustard. Her partner Robert is too. It’s actually central to their whole relationship, at least in terms of condiments.

EVELETH: We have a running joke, because I subscribe to the Mustard Museum’s newsletter, and it’s sort of full of mustard information. And a couple of years ago, they sent one out and that was, like, you know, we do weddings. And I don’t know if they were serious or not but we have a running joke about getting married at the Mustard Museum.

GRABER: Nicky, you and I did not have wedding plans.

TWILLEY: Because we’re already work married.

GRABER: But we did actually visit the Mustard Museum. It’s just outside Madison, Wisconsin, and we happened to be in town to do a Gastropod live show. When in Madison, go see mustard, apparently.

BARRY LEVENSON: So anyway we’re going down into the museum: the world’s largest collection of mustard, mustard memorabilia, and fine mustard art.

TWILLEY: Barry Levenson is the founder and curator of the National Mustard Museum. He’s a lawyer with a serious mustard obsession.

LEVENSON: We’ve got nearly 6,000 different mustards here. So, in addition to American yellow mustard, classic French mustard, you have horseradish mustard, you have whole grain mustards. We have hot pepper mustards. We have herb mustards, we have fruit and vegetable mustards. We have garlic mustard. We also have spirit mustards, which would be mustards made with beer, with wine. We have exotic mustards. The exotic mustard category can be anything from curry mustards to truffle mustards to mustards with ginger. Right now, we’re standing in front of some of the French mustards.

TWILLEY: But before things get even more insane—although personally I think getting married at the mustard museum is already pretty insane, and having 6,000 jars of any condiment is definitely a warning sign—we need to back up. How did we get from garlic mustard seed stew to the condiment-filled jars we know and some of us love today?

GRABER: Before we clear your sinuses with some strong Dijon, we have a sponsor to tell you about.

(MID-ROLL)

GRABER: To get to France, first we have to go back to ancient Egypt.

LEVENSON: We also know that the ancient Egyptians would chew mustard seeds along with their meats and that would flavor it. But they would just take the seeds, because mustard seeds themselves are inert.

TWILLEY: There’s actually a chemical trick to mustard. So: the glucosinolates in mustard seeds—they’re slightly different compounds in black vs. yellow vs. brown mustard seeds but they work the same way. Which is that they they react with a particular plant enzyme in the presence of cold water to produce that fiery essential oil of mustard. This multi-step trigger process is another way that the plant holds fire until the caterpillar actually crunches into it and sets off that reaction.

LEVENSON: It’s only when combined with some liquid do they release their heat and their pungency. As a result, that’s what the Egyptians would do. They’d say, okay, have some meat and chew on some mustard seeds.

GRABER: Then the Romans decided to turn mustard into a sauce.

LEVENSON: We know that the Romans were using mustard seeds in some of their sauces and then that migrated into the Roman Empire, specifically into the area now known as Dijon, where the monks were making pretty much what we know as mustard today back in the 12th and 13th centuries.

TWILLEY: The first reference to mustard in the Dijon archives occurs in 1336—it’s a record of a whole cask of mustard being consumed at a banquet. So mustard was already a big deal. The first ordinance specifying how to make Dijon came at the end of that century. Basically, soak the seeds, crush the seeds, and then add vinegar to the paste. To go back to our chemistry for a minute, using an acidic liquid like vinegar puts a brake on the reaction, which gives the resulting mustard a long-lasting, slow burn—as opposed to the quick, pungent hit of mixing it with water.

GRABER: Dijon mustard got super popular in 1756. That’s when a major mustard maker in Dijon changed his recipe from vinegar to verjus—it’s a juice made from unripe grapes, and it’s not quite as acidic as vinegar. Today, if you buy Dijon mustard, it doesn’t usually have verjus, but the makers still try to make it taste like the recipe that made it famous. They’ll often use a combination of white wine and vinegar.

TWILLEY: Technically, Dijon is supposed to only be made with either black mustard or brown mustard seeds. But basically nobody uses black mustard commercially because the seed heads are so fragile that you have to harvest it by hand.

GRABER: Seventy to eighty percent of the mustard seed exported to make condiments comes from industrial fields in Canada, which happens to be the world’s mustard basket. And Barry says a lot of those mustard seeds go to France.

LEVENSON: France, of course, is known for mustard. The per capita consumption of mustard in France is greater than any other country.

TWILLEY: Since the 1800s, Dijon has been found at tables throughout France. In my home country, though, we developed a rival: Tewkesbury mustard, which is mustard mixed with its close cousin, horseradish, for a little extra something something. This mustard was sold and transported dry in balls, known as Tewkesbury fire balls. They were a staple in English kitchens in the 1600s.

LEVENSON: Shakespeare loved mustard and wrote about mustard in several of his plays.

GRABER: Shakespeare even used this famous Tewkesbury mustard in one his slightly less famous plays, King Henry IV Part 2. He wrote, “His wit’s as thick as Tewkesbury mustard.”

TWILLEY: This is not a compliment.

GRABER: Barry has his own favorite Shakespearean mustard quote.

Barry: “What say you to a piece of beef and mustard? Aye, a dish I do love to feed upon,” from Taming of the Shrew.

TWILLEY: Here’s the Shakespeare mustard reference I found surprising though: eye of newt, which is one of the things the witches stir into their cauldron in Macbeth—”eye of newt and and toe of frog, wool of bat and tongue of dog,” etcetera, etcetera. So eye of newt—I always thought that was the eye of a newt. But it isn’t! It’s an old name for a mustard seed.

GRABER: Rose, the rabbit holes you’ve sent us down! But Shakespeare’s Tewkesbury isn’t the most famous British mustard today.

LEVENSON: That would be Colman’s. The classic hot, just good, strong mustard that just kind of goes right up in the nose.

TWILLEY: Colman’s in the yellow tin—it’s *the* British mustard.

LEVENSON: Yeah, Colman’s dry is kind of the gold standard.

TWILLEY: The thing about Colman’s is, as Barry points out, it was originally a dry mustard—and you can still buy it that way today. I have two tins of Colman’s mustard powder in my kitchen as we speak. But grinding and selling dry mustard as a powder—that actually wasn’t Jeremiah Colman’s idea.

GRABER: The inventor of powdered, dry mustard is lost to history. The only record comes from an article published in 1807, in the Gentleman’s Magazine. And the author wrote that, in 1720, quote, “it occurred to an old woman of the name of Clements, resident at Durham, to grind the seed in a mill and to pass the meal through the various processes which are resorted to to make flour from wheat.”

TWILLEY: Ms. Clements’ mustard flour was a huge hit. Even George the First gave it the thumbs up. But she kept the secret to herself for many years. Jeremiah Colman was originally a flour miller, with a mill of his own. He didn’t turn to mustard until nearly 100 years after Ms Clements’ big breakthrough. But then he conquered the British mustard market, with a special blend of locally grown white and brown mustard seeds ground to a fine powder.

LEVENSON: Colman’s mustard was just dry mustard for the first 60 or 70 years before someone decided at Colman’s, well, why don’t we actually make the mustard condiment?

GRABER: So while Dijon is made from brown mustard seed, Colman’s is a blend of white mustard and brown mustard seeds. Brown seeds, like the ones used in Dijon mustard, they give you more of a horseradish-y, sinus hit.

LEVENSON: It gives you more of that nose hit as opposed to the yellow seed, which is more pungent just on the tongue.

TWILLEY: So France has its favorite mustard, Dijon, England has Colman’s, but in America, it’s all about French’s. So what’s that?

LEVENSON: That came about a little over 100 years ago, when Mr. French decided that even though there were European mustards, they weren’t all that popular. What this country needed was a brightly colored, happy mustard and that’s what French’s mustard has been.

GRABER:  Actually French’s mustard—it first came out at the turn of the last century—it was originally called “French’s Cream Salad Brand.” Not only was it bright yellow because Mr. R. T. French added turmeric to the recipe, but it was also creamier and sweeter. And it was a huge, huge hit almost instantly in America.

LEVENSON: It is generally made with the yellow seed, so it is going to have a very different kind of flavor profile. And that’s the kind of thing that when you go to the ballpark, I think you’ve got to have yellow mustard at least on that first dog. Because you hold up the hotdog, you know, and you see the blue sky, the green grass, the brown base paths and there’s just something about that yellow squiggle of mustard that makes life so worth living that day.

GRABER: Oh Barry.

TWILLEY: People have strong feelings about mustard.

MADHUR JAFFREY: It’s very important and it’s an ancient seed that we’ve had forever.

GRABER: Madhur Jaffrey is an actress and food writer. She’s probably the most famous writer of Indian cookbooks—she’s the person whose cookbooks helped popularize Indian cooking at home in the West.

TWILLEY: We’ve been stuck in Europe and America so far this episode, but mustard is global. And India has its own serious, long-term mustard thing going on. It’s not a condiment-based relationship, but it’s central to Indian cuisine

JAFFREY: It’s been amongst our two hot spices that originated in India. We started out thousands of years ago with mustard seed and black pepper. Those are native to the region and those were the only spices we had that were hot, and chiles of course came much later. So for many centuries, they were even more important than they are today, but they’re still very important today, because one of the oils that we cook with, which is very important, is mustard oil.

GRABER: Mustard seed and, even more importantly, mustard oil is found in kitchens throughout the Indian subcontinent.

JAFFREY: It’s used for cooking a lot of food in several states. Bengal cooks a lot with mustard oil. Kashmir cooks a lot with mustard oil. So these are two states where it’s almost the state oil. And there are certain dishes that would be cooked always with mustard oil. If you’re steaming a fish, you will definitely use some mustard oil. In Bengal, if you are making this muri, which is puffed rice, you’ve puffed it and then you want to dress it quickly with different things, you’ll put, among other things, mustard oil on it and have it for breakfast.

TWILLEY: So but here’s what’s weird. Mustard oil is banned in the U.S. as a food. It has been since the 1990s.

JAFFREY: When I buy mustard seed oil, it says on top: “Use for external purposes only.” People in India eat it and survive and nothing happens to them and they live long lives. We put it on babies, we—you know — but externally we put it on babies. But I keep reading it and ignoring it. It’s just like what they used to say with coconut oil. “Don’t cook with coconut oil.” And people go through fashions and suddenly now everybody is cooking with coconut oil as if it’s the best thing in the world.

GRABER: You might think that maybe the U.S. government was afraid of those pungent, insect-fighting glucosinolates. But no. The FDA thinks the problem comes from a fatty acid that’s found in the seed. Apparently tests on rats show that in high doses this particular fatty acid can cause heart lesions. But frankly, as Madhur says, literally billions of people have been cooking with mustard seed oil for thousands of years.

JAFFREY: I wouldn’t give it up. No. It is in a lot of things that I cook. I cook everything from all over India and I use it all the time.

TWILLEY: For Madhur, the magic of mustard is in the way you can manipulate its heat.

JAFFREY: It’s like a Jekyll and Hyde of both spices and oils. If you use it plain, it’s quite pungent. So when we want that pungent flavor, we use it plain. But if you heat the oil or if you pop the mustard seeds, they turn sweet and nutty. So it depends on what we want. It can change its shape, as it were.

GRABER: So in India, cooks know that cooking heat tames the fieriness of mustard seeds and oil. But Barry says condiment markers can use other tools to manipulate that heat, too.

LEVENSON: Which seed you use, how much water, how much vinegar is going to be used. There are all kinds of ways that mustard makers are able to change the heat of the final product.

TWILLEY: In fact, mustard is surprisingly nuanced. You think of it as this blast of heat on a sandwich, but, depending on how you make it or how you pair it with food, mustard doesn’t have to steal the show—it can fade into the background and just make everything else taste better.

GRABER: I never really had strong feelings about mustard one way or the other, unlike all of our guests this episode, but the bagel shop near me uses mustard butter on their bagel-egg sandwich and it’s mind-blowing. So I also started using a layer of mustard in my savory galettes—these are free-form pies—and it totally ups the game.

TWILLEY: Whole-grain mustard smeared inside the pastry shell of a quiche, before you add the filling: unreal. And mustard powder is my secret ingredient in cheese straws. But Barry and Rose have taken this pairing game a little further.

LEVENSON: It’s something that you can also use in brownies because it accentuates the flavor of chocolate.

EVELETH: This is going to sound disgusting to a lot of people but I think it’s delicious: a little bit of mustard on Oreos is extremely good.

GRABER: Wow, that is an unusual one.

TWILLEY: Wait, wait, wait so are we talking like French’s here or what are you doing? Like, how is that?

EVELETH: Like you sort of dip a double-stuffed Oreo into like, a little bit of mustard, in Dijon mustard.

GRABER: And what does that do for the Oreo?

EVELETH: Well, because the Oreos are so sweet, right? Like, you’ve got the chocolate cookie and then you’ve got that, like, really saccharin middle chemical bit—like, I don’t know what it is—

GRABER: The white part.

EVELETH: The white part—it’s so sweet that just a little bit of like spiciness or that little bit of, like, mustard flavor is really a good foil to the Oreo. It’s delicious. I know everyone listening is going to be, like, you’re a psychopath. But I love it.

GRABER: I totally want to try this.

EVELETH: It’s really good.

TWILLEY: I might skip mustard Oreos. But I’m much more into Rose’s most recent mustard revelation.

EVELETH: I have been really into making Bloody Marys recently, and I put a little bit of mustard in my Bloody Mary mix.

TWILLEY: Wait, the spread or the powder?

EVELETH: So I’ve been experimenting with both. So I will put a little bit of powder in the ring, like, the ring that you put on the glass.

TWILLEY: Oh yes, that does sound really good.

EVELETH: And then a tiny bit of it in. Yeah, it’s super good. You have to be careful because you could definitely overdo it with mustard powder particular. But I also put a little bit of Dijon in the actual sort of concoction, the tomato paste concoction that I used to make Bloody Marys. I’ll make you Bloody Marys any time, they’re my favorite drink and I’m really into making them.

GRABER: I’m so there!

TWILLEY: And that’s it for today’s episode because we have somewhere to be! There is a mustard Bloody Mary calling my name.

(MUSIC)

GRABER: Thanks this episode to Rose Eveleth. She is the host of a fascinating podcast called Flash Forward—it’s all about possible and not so possible futures. She had a recent one on a future where we’re all telepathic, and another scary and possible one about what happens if the census goes haywire.

TWILLEY: Thanks also to Patrick Edger of Michigan State University, Hayley Saul of Western Sydney University, and Madhur Jaffrey, legendary food writer and actress. We have links to their work on our website, gastropod.com. And, finally, thanks to Barry Levenson of the National Mustard Museum in Middleton, Wisconsin.

GRABER: We’ve got some more fascinating mustard stories involving mustard gas, mustard plasters, and mustard sounds saved for our special sustaining supporters newsletter: if you’re able to donate $9 a month on our website or $5 per episode on Patreon, you too could enjoy some more mustardy goodness!

(POST-ROLL)

GRABER: We’re back in two weeks with a few famous friends. Yep, we’re hanging with Nigella and Yotam and we’re name-dropping like we just don’t care!