The strange thing about that night was no one liked my mustard chicken. I could tell from the silence around the table. It was not a contented silence and I was frustrated, because mustard chicken is usually a hit in our house, and nothing was all that different this time. I used the same chicken, the same big spoonful of mustard in the sauce.
The mustard did come from a new jar, but it was the same brand I buy every time, Maille Dijon Originale. It’s luscious and smooth. Sometimes, I’ll eat a whole spoonful by itself.
Later, unable to help myself, I returned to the jar and had a taste. It was much, much stronger than usual. My cheeks flushed. My eyes watered.
For weeks afterward, whenever I opened the fridge, a question gnawed at me: Why is this mustard so spicy?
Eventually, I packed the jar in a cooler and went to see Elspeth Copeland, a professional taste tester and product developer I know in Toronto. She has the best palate I’ve encountered in 10 years of writing about the food industry. North American food brands call her when their product suddenly, inexplicably changes — a surprisingly common occurrence in food manufacturing — and she can usually identify the problem in the factory or the supply chain just by tasting the product. Once, I watched her eat a cherry and deduce that a cherry salesman likely left the fruit too long in the back seat of a car.
That morning in February, she brought me into her kitchen and handed me a plate. It was my job to set up the blind taste test, so she could compare my jar against a control sample from the same brand.
“Do a little dollop,” she said, then turned her back so I could do my work in secret.
I spooned the mustard from my jar onto a plate, and some from another jar of Maille I found in the grocery store that morning. She tried the sample from my jar first and sputtered a little.
“It’s quite spicy,” she said.
I asked her how much spicier it was than the control jar.
“Like, 10 times,” she said.
The other one produced no nasal burn, no watering eyes, no sputtering. Copeland was intrigued. Global consumer brands don’t normally tolerate major variances in the flavour profile of their products.
“This is significant,” she said, squinting at the mustard.
She poked at the samples on the plate, rubbed them between her fingers, compared the colour and read the expiry dates on the jars.
She took another taste of the spicy jar.
“Oooo,” she winced.
I left her house that morning certain that we were onto something. But at that moment, I did not realize just how deep it would go.
Copeland sent me to talk to Demet Güzey, who worked for seven years at Unilever, the global consumer products giant that owns Maille.
Güzey left Unilever in 2014 and has since published “Mustard: A Global History.”
I described my situation and she was skeptical that Maille would make such a spicy jar by mistake. Big food manufacturers set targets for spiciness. They have labs and conduct taste tests to make sure the product lands within the acceptable range.
“I’m guessing that they wanted it this way,” she said.
It wouldn’t be out of the ordinary for the same brand to taste different from region to region, or even store to store. Global brands switch up their recipes depending on regulations and preferences in each region. One brand of mayonnaise in one country might use whole eggs and sunflower oil, she said, but the same brand will use egg yolks and soybean oil in another country.
In some cases, brands change their recipe because a specific retailer asked them too. Costco is famous for this. Earlier this year, the food publication Delish found that Oreos from Costco were slightly different — less salt, more natural flavourings — than other Oreos from other stores in the U.S.
Jessica Jones, vice-president of supply chain at Kraft Heinz Canada, told me that Costco is known to ask for “slightly elevated” versions of products.
“They like unique formulas,” she said. “I don’t know if that is the case here.”
As she spoke, I started to shake.
My jar was from Costco.
I asked her how I would be able to tell if my jar was a special Costco variation.
“They don’t usually say ‘better than the others,’” she said. “It’s almost a little bit of a treasure hunt.”
The only real hint, she said, is usually hidden in the nutritional information, maybe just a few extra grams of protein.
When the call ended, I ran to the fridge, grabbed my jar of mustard and started comparing stats with a regular, non-Costco jar of Maille.
Calories: 5. The same.
Fat: 0.5 g. The same.
Protein: 0.4 g. The same.
Everything, the same.
It appeared I’d hit a dead end.
I needed to start at the beginning.
Maybe the freshness had something to do with the heat. But to find out when it was made, I had to crack a code printed in small type on the jar:
#23106 2027/APR/07 L52870D757 06:56
This type of code is meant to be indecipherable to the mustard-eating public, aside from the expiry date in the middle. But there was crucial information in it, including the exact time of production, to aid manufacturers in the event of a product recall.
Manufacturers use different formats, but if you’ve seen enough of them, you can venture an educated guess. I asked Copeland, who has spent 30 years in the food industry, for help. She focused on four digits near the middle: 5287.
The 5 probably indicated the year of production, 2025. And 287 would be the Julian date. That meant my mustard likely was made on Oct. 14 — the 287th day of 2025 — at 6:56 a.m.
So I had managed to get my hands on an incredibly fresh jar of mustard, still firmly in the spring of its life, just 127 days old when we conducted our tests in February. It was more than a year away from its expiry date. The control jar was almost twice as old.
“Mustard is hotter/spicier the fresher it is,” Copeland wrote to me after our tests.
In a way, it made sense. But it didn’t feel right. The mustard was just so spicy. I had a hunch something else was going on.
Then, a package arrived.
I’d been talking with Marc Désarménien, the head of one of the last mustard dynasties in France. His grandfather was Edmond Fallot, namesake to a prominent mustard brand in Burgundy. In photos, he has thick, salt-and-pepper hair and wears dark suits.
He runs La Moutarderie Edmond Fallot in Beaune, which is close enough to the city of Dijon to be counted as part of the classic mustard tradition. (My favourite fact about the city of Dijon: it is home to La Confrérie de la Moutarde de Dijon, or the Dijon Mustard Brotherhood. They wear medieval-style, yellow waistcoats and capes, and hold conferences and debates to defend and promote mustard, according to the brotherhood’s website.)
Désarménien told me something that changed the way I thought about mustard.
“We are not Heinz,” he said over the phone. “We are not Coca-Cola.”
He described mustard as a living thing. It comes from plants and like all living things, it changes.
“Man cannot control everything in a plant,” he said. “You have small differences. It’s not big differences. But that’s life, you know?”
I told Désarménien about my situation and he mailed me a jar of Edmond Fallot Dijon mustard, fresh from his factory, so I could test our freshness theory.
His brand is generally stronger than Maille, he said. And a fresh jar should be much stronger than my jar, that had been sitting in a fridge since Christmas.
“For me, a good Dijon mustard has to be strong,” he said over the phone one morning in July. “I love to eat strong Dijon. I prefer to eat it when it’s fresh.”
The Fallot mustard arrived by courier a few days later, wrapped in protective foam. It was less than two months old, produced in mid-June.
By comparison, my jar of Maille mustard was about 10 months old. It didn’t stand a chance, I thought.
I tried the new Fallot mustard and immediately felt a hot burst on my tongue. But it wasn’t painful, not even for me, with my admittedly feeble tolerance for heat. I took another spoonful, just for the fun of it.
I rinsed my mouth then turned to the old jar of Maille mustard. A flash of heat hit the front of my face. There was violence in my mouth. I blinked and blinked.
“Woah,” I said.
It looked like my hunch was right. Freshness was not the only factor at play.
Canada is the top exporter of mustard seeds in the world.
Most of it grows in Palliser’s Triangle, a vast region named after the British surveyor who thought no crops could thrive there. The triangle starts in the southwest corner of Manitoba, stretches up across the bottom half of Saskatchewan and swoops down into Alberta.
From the Prairies, the seeds are cleaned, graded and shipped to food manufacturers around the world. Unilever wouldn’t tell me where Maille sources its seeds, but industry insiders said most of the major French mustard producers, including Unilever, get at least some mustard seeds from Canada.
“They absolutely do,” said Dave Macfarlane, a mustard executive who chairs the Canadian Mustard Association, when I asked him if Unilever buys Canadian mustard seeds. “Without question.”
Canadian mustard ends up in a lot of things.
G.S. Dunn, one of the biggest mustard mills in the country, grinds mustard into powder at its facility in downtown Hamilton, Ont., to be added to barbecue sauce, mayonnaise and salad dressings. It can be used in batters and wasabi paste and as a binder in sausages and hot dogs.
I went there to visit Andrew Mansfield, G.S. Dunn’s technical director. He is a careful man who thinks deeply about his work, so much so that he keeps a close eye on online discussion boards dedicated to mustard.
“Mustard is like a weird secret society that no one knows anything about,” he said.
I explained my quest for answers about the jar of mustard, and he said he’d seen a similar complaint on Reddit.
Later, I found a post from around the same time I bought my jar at Costco. The post, to the r/CostcoCanada subreddit, was titled: “Anyone else find the Maille Dijon mustard much stronger than usual?”
The poster, jonf00, used the mustard from a new Maille jar from Costco in a salmon marinade, without tasting it first. “My toddler started crying and threw it all over the dining room,” they wrote. “It was almost like pure horseradish strong.”
As we entered the mustard mill, I asked if I should brace myself for the smell.
“I’m almost certain,” Mansfield said, “it’s not going to smell like what you’re expecting.”
I expected something acidic and mustardy, but it smelled sweet, like wet hay. The garbage cans were painted yellow, and the ladders, and the broom handles, and shovels and dust bins, as if management had surrendered to the thick yellow mustard dust that covers everything in the factory.
Staff at the plant need to be careful not to exert themselves too much. If they start to sweat, the moisture mixes with the dust and could cause serious burns on their skin.
“It’s like a sun burn,” said Joe Araujo, a miller at the plant for 35 years.
The skin burns come from glucosinolates. They’re thought to be the plant’s defence against predators. But glucosinolates are also what give Dijon its heat, what make arugula peppery and what give horseradish its kick.
Around 2020, Véronique Barthet noticed something was happening with glucosinolates. She works as a research scientist with the Canadian Grain Commission, the federal agency that monitors the quality of grain exports. There’d been studies out of Australia that looked at canola — another member of the Brassicaceae family — and found glucosinolate levels rose in hotter, drier growing conditions.
If that happened in Canada, it would be trouble. Canadian cattle eat a lot of canola meal, and they do not like it when glucosinolate levels rise. Barthet and her team in Winnipeg did their own tests and found the same trend was happening in Canada.
She decided the commission needed to keep a closer watch on glucosinolate levels. They analyzed more crop samples from around the Prairies, including mustard seeds.
Around the same time, the Palliser’s Triangle started getting hotter and drier. The drought dragged on for roughly five years, and during that time, Barthet and her team were watching the mustard closely.
This spring, the commission announced its findings: There has been a “notable increase” in the spiciness of the Canadian mustard crop.
“As summers on the Canadian Prairies get hotter and drier, the seeds used to make the mustard for our hot dogs, sandwiches and dressings are getting spicier,” the commission said.
In a LinkedIn post, the commission warned that glucosinolate levels could stay high as climate change makes hot, dry conditions more common.
“The taste of mustard seeds will be further affected,” the commission said, “and food manufacturers may need to adjust their recipes.”
But Dijon mustard is tough to adjust. It is only three main ingredients: brown mustard seeds, water, and wine or vinegar. If the seeds get spicier, there’s not many ways to bring the heat back down. Add more water and the mustard gets soupy. Add more vinegar and it gets tart. Some mustard makers can cook the mix longer to mellow the seeds, or reduce soaking times, or mix in seeds from milder regions. But sometimes, despite such efforts, the end product just gets hotter.
Barthet believes two things caused the extreme spiciness in my jar. First, it was very fresh when I tasted it. Second, the mustard was made from seeds with higher-than-usual glucosinolate levels, due to the recent growing conditions. This is not a uniquely Canadian problem. Higher temperatures would mean spicier seeds in other growing regions too.
Others in the industry had the same thought. But I still wanted hear from Unilever directly. For weeks, I tried to contact the company’s global press office in London and heard nothing.
I visited the Bloor Street headquarters of Unilever Canada. No one would talk.
“I beg you,” I wrote in one email. “Please find it in your heart to answer a few of my questions.”
Then it happened. I received a response from Brandon Collins, corporate executive chef for Unilever North America. On Instagram, Collins describes himself as a “Maille Mustard Sommelier.”
In his note, he confirmed my theory.
“Mustard is a naturally grown plant,” he said, “and like grapes used in winemaking, its flavour can vary from harvest to harvest.”
He acknowledged that temperature and drought can influence the seed, and said Maille manages the changes through the “mustard-making process and choice of ingredients.” But Maille doesn’t use additives to artificially standardize the flavour, so some variation happens.
“Those with particularly attuned palates may therefore notice subtle differences in flavour or intensity from one batch to another — part of the character of a product made from a living agricultural ingredient,” he wrote.
I finished reading, stood up from my desk and walked out into the street. It was warm and I felt a lightness. My mind wandered to non-mustard places. It was over. I was free.
