You Can Ferment That: Mustard

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homemade mustard in a jar

This article was originally published in the July/August 2023 Zymurgy magazine. Access the Zymurgy online digital archive.

By Dave Carpenter

When it comes to Belgian cities, Bruges consistently takes the top spot for Instagrammable charm. With its winding canals, well-preserved medieval architecture, and pubs lurking around every corner, Bruges’s romance and charm are undeniable. As Harry observed in In Bruges, it is a “fairytale f***ing town.”

I like Bruges, but if I only had one day in the area, I would choose Ghent. For one thing, Ghent is slightly less crowded. Ghent also has Gravensteen castle, a well-preserved heap of medieval stones that features Europe’s most entertaining audio tour. There’s also plenty of excellent beer to be had at such venerable haunts as Dulle Griet, Het Waterhuis aan de Bierkant, and other equally impossible-to-spell venues.

My preference for Ghent, though, is largely so I can hand over fistfuls of money to the condiment clerks at Yves Tierenteyn-Verlent, who produce what has been called the finest mustard in the world. Ghent’s famous mustard firmly but respectfully punches the nasal cavity before yielding to a smooth flavor that leaves one pining for more. Tierenteyn-Verlent mustard is only for sale in the company’s Ghent shop at Groentenmarkt 3 and at certain retailers in Belgium and The Netherlands.

If a trip to Belgium is in your future and you enjoy mustard, do yourself a favor and pick up some of this world-famous condiment while you’re in Ghent. If, however, you are like me and unsure when your next European vacation might be, you can do the next best thing and make your own mustard.

Now, I don’t even begin to suggest we can clone Tierenteyn-Verlent’s mustard any more than we could clone a Magritte. We can aim for something close, but ultimately, ceci n’est pas la moutarde. However, homemade mustard can satisfy our own personal tastes much better than anything sitting on the grocery shelves right now.

Mustard Varieties

The two types of mustard seed you’ll most commonly encounter are white mustard (Sinapis alba) and brown mustard (Brassica juncea). Black mustard (Brassica nigra) is less ubiquitous in North America but is an essential component of Indian cuisine. White mustard is the mildest, brown is considerably more pungent, and black can be downright punishing if you’re not careful.

Prepared mustard, the condiment, can come in any number of forms and is infinitely adaptable. Here are a few of the most common varieties you might come across in your local supermarket.

  • American yellow mustard: This is the stuff you grew up with. It probably comes in a yellow squeeze bottle, and it is the only valid condiment for ballpark hot dogs. The bright yellow color comes from generous additions of turmeric.
  • American “deli” mustard: This is the stuff you might generically call brown mustard. It’s spicier than the standard-issue stuff and complements deli meats very well, hence the appellation.
  • Whole-grain mustard: This is the stuff that features whole seeds suspended in its mustardy matrix. The presence of whole mustard seeds isn’t necessarily an indication of pungency, but in general, these tend to be middle of the road, not too hot, not too mild.
  • Dijon mustard: This is the stuff you ask for when your Rolls-Royce pulls up next to another Rolls-Royce at a traffic light in the 1980s. Its signature acidity comes from the addition of white wine or, historically, verjuice. Its signature snob appeal comes from marketing executives.
  • Chinese mustard: This is the stuff that comes in the little packets that accompany egg rolls and crab wontons from your favorite takeout spot. It’s powerfully hot and, if done right, can make your eyes roll back in your head.
  • English mustard: This is the stuff that you serve with English roast beef. Like Chinese mustard, it packs quite a punch. Jacob Marley might have been a blot of it.
  • Bavarian sweet mustard: This is the stuff that accompanies the Weisswurst, pretzel, and Weissbier in a traditional Bavarian breakfast. Like the Bavarians themselves, this mustard is sweet but not spicy.
  • Düsseldorfer mustard: This is the stuff that comes in a miniature beer mug at World Market. It’s not as powerful as Chinese mustard, but it’s considerably more pungent than plain American yellow.

These are what I consider “foundational” mustards, any lineage of which can be further bifurcated with honey, spirits, beer (!), spices, and so on to head in whatever direction you want to take it. Note the absence of a Ghent-style mustard. That’s because there isn’t one. Ghent-style mustard is just easier to say than Tierenteyn-Verlent.

Tips for Preparing and Fermenting Mustard

You can certainly make a great mustard using water or vinegar alone, but as this is Zymurgy, we’re going to ferment ours. It’s not terribly difficult. You need only prepare a brine of sufficient salinity to discourage growth of mold and spoiling bacteria. Mix crushed mustard seeds in said brine and allow it to sit at room temperature for a week or more.

Mustard seeds are less likely than vegetables to grow mold and other nasties, but it’s still worth considering a fermentation weight to keep all the seeds submerged during fermentation.

Mustard seeds on their own don’t have much pungency. Even grinding them into powder won’t get you there. It’s when mustard seeds come into contact with liquid that the enzyme myrosinase begins its work, revealing the sinus-clearing magic within. It takes about 10 minutes to reach peak pungency. For the spiciest of mustards, hydrate crushed seeds or powder only with cold water, as heat renders myrosinase less effective.

Hydrating with acidic liquid such as vinegar or white wine tempers enzymatic activity and, thus, the final pungency. It also helps stabilize the product, which is why prepared mustard almost always includes an acidic component.

Fermentation gets you a little bit of both worlds. Initially hydrating with a cold brine activates myrosinase. As fermentation progresses and lactic-acid bacteria render the environment increasingly acidic, the resulting acidity serves to naturally stabilize the heat and flavor.

Fermenting mustard has the potential to smell like rotten eggs. Storing it in your bedroom is, of course, ill-advised, but even keeping it in your kitchen may yield some aromatic surprises when you come home from work. You could always use a charcoal-filter airlock hack (, but since the smell only lasts a couple of days, it’s easiest just to find some out-of-the-way corner in which to hide it until the worst is behind you.

Once you’ve determined that your fermentation is complete, it’s time to blend, season, and adjust for texture. This is where you can really steer your fermented mustard in a direction that pleases your palate and tickles your nasal cavity.

This is less about adding specific amounts of any one ingredient than it is about taste, adjust, and repeat. Do it a few times and you’ll get the hang of it.

First assess what nature has given you. How salty is it? How acidic? Is there enough spicy heat or do you need more? These elements are adjusted with additions of salt, water or vinegar, and dry mustard powder.

I recommend starting by blending your lacto-fermented mustard to your desired level of smoothness. Unless you want an incredibly thick product, you’re going to need to add some liquid to thin it out. This is where you choose to thin with water, vinegar (I like white wine vinegar), or a blend of the two. Choose vinegar to gain more acidity, or choose water to temper the acid that’s already there. There may be some back and forth until you hit the texture you want.

Now season with additional salt if desired, and add dry mustard powder if you want more bite. Remember to wait about 10 minutes between dry mustard additions, as it takes about that amount of time for the enzymes to work their magic and fully express the level of heat.

If you’ve yet to tackle any of the other beer-adjacent ferments in Zymurgy, might I suggest you give mustard a try. Whatever you end up with is guaranteed to be a cut above.

Homemade Fermented Mustard Recipe

Recipe by Gabe Toth, reprinted from The Fermentation Kitchen.

This is not the yellow mustard you might be used to. The ground mustard seed (Colman’s is a commonly available brand) packs some punch, similar to the spice that horseradish has.


  • 50 g whole mustard seed (yellow, brown, black, or a combination)
  • 60 g ground mustard seed
  • 7.8 g salt
  • 150 g water
  • Herbs, garlic, chiles, or chile powder (all optional)


Pound the mustard seeds lightly in a mortar and pestle, just to break them open. Mix all ingredients in a pint jar. Cover jar with a lid and let ferment for a couple of weeks, then put into the fridge.

Dave Carpenter is editor-in-chief of Zymurgy.

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