Wasabi: Real vs Fake, and What You Have Actually Been Eating

The green paste that arrives beside a plate of sushi is, more often than not, not wasabi. That is not a hot take or a piece of gatekeeping — it is a manufacturing fact, and once you know what the real thing is and how it behaves, the substitute stops being a scandal and starts being a slightly sad convenience.

Here is the plant, the chemistry, the reason it costs what it costs, and the honest position on what is in the two dishes on our own menu that print the word.

It is not a root, and it is not a horseradish relative by accident

Wasabi is Eutrema japonicum, of the family Brassicaceae — the mustard and cabbage family. That family membership is the whole story of how it tastes, because the pungency mechanism it uses is the mustard family’s mechanism, not the chilli family’s.

The part used for the paste is commonly called the root. It has been more accurately characterised as the rhizome, or the stem, or — most precisely and least conveniently — the rhizome plus the base part of the stem.

What is in the tube instead

Outside Japan, the standard replacement is a mixture of horseradish, mustard, starch, and green food colouring or spinach powder. Packages are often labelled as wasabi while the ingredients include no part of the wasabi plant at all.

You will see a widely repeated statistic about what percentage of wasabi sold worldwide is fake. We are not going to give you that number, because we could not find it in a source we trust. What is documented is the substitute’s recipe and the labelling practice, which is enough to go on.

The heat is a chemical reaction, and you start it by grating

This is the part that explains everything else.

The pungent compound is allyl isothiocyanate, which is produced by hydrolysis of allyl glucosinolate. The reaction is catalysed by an enzyme, myrosinase, and it happens when the enzyme is released on cell rupture — that is, when the tissue is crushed.

The heat does not sit in the rhizome waiting. The grating is the cooking. You are not preparing an ingredient, you are running a reaction, and the clock starts the moment you do.

Which is why the traditional tool is not a knife or a blender. The fresh rhizome is grated into a paste and eaten in small amounts at a time; traditionally on coarse sharkskin, and in modern kitchens on metal graters called oroshigane. And it is why fresh wasabi paste loses its flavour quickly if left uncovered, and why some high-end restaurants grate it at the moment of service rather than in advance.

A tube does not have this problem, because a tube has nothing to lose.

Why it burns differently from chilli, and what to do about it

Wasabi heat goes up the nose and vanishes. Chilli heat sits on the tongue and stays. That is not a matter of intensity; it is a matter of solubility.

Because the burning sensations of wasabi are not oil-based, they are short-lived compared with the effects of capsaicin in chilli peppers, and they are washed away with more food or liquid. The practical instruction follows directly: if wasabi has got you, keep eating. If chilli has got you, water will not help and you have a longer wait.

This also explains why it works as a seasoning rather than a challenge. A chilli heat has to be budgeted across a dish because it accumulates. A wasabi hit resets between mouthfuls, so a kitchen can put it in a sauce and rely on it landing the same way every time.

Why the real thing is expensive

Not scarcity theatre. Agriculture.

Wasabi favours growing conditions that restrict its wide cultivation. It is quite intolerant of direct sunlight. It wants an air temperature between 8 and 20°C, and high humidity in summer. Where it is grown in water, the optimal water temperature is 10 to 13°C. Singapore, for the avoidance of doubt, is none of those things on any day of the year.

In Japan the named growing areas include the Izu Peninsula in Shizuoka Prefecture, Nagano Prefecture — including the Daio Wasabi Farm at Azumino — Iwate and Shimane. It is also cultivated in Western Canada, Oregon, North Carolina, Tennessee, Iceland, the Netherlands, Hungary and the UK, which is a list of cold, wet places and no coincidence at all.

What the sushi counter is telling you

Sushi chefs usually put the wasabi between the fish and the rice, in order to cover it and preserve its flavour.

That single habit is the best evidence for everything above. If the flavour were stable, its position would not matter. It is placed where it is protected, because it is volatile and it is on a clock. Whatever you have been told about the etiquette of soy sauce, the chef’s own hands are making the argument: this stuff degrades, so it goes where it will last longest.

It is on our menu twice, and nowhere near a fish

We are a Japanese–Middle Eastern grill, not a sushi counter, and the two places the word appears on our card are both places nobody would expect it. Printed as the menu prints them:

• KIBBEH NAYYEH — margra lamb tartare, shio kombu, wheat, wasabi ponzu vinaigrette, crispy things, salted cambodian black pepper.
• MANGALICA PORK COLLAR CHOP & BEANS — fennel spice, wasabi & butter bean mash, charred vinegared radicchio, tonkotsu jus.

Both are the same idea, applied to fat. Raw lamb and a fatty pork collar have the same problem: richness with nothing to interrupt it. A heat that arrives high in the nose and then clears is a very precise tool for that, in a way a chilli heat is not, because chilli would still be there on the fourth mouthful when what you wanted was a clean start.

The lamb dish is a Levantine raw preparation with a Japanese vinaigrette on it, which is the whole restaurant in one plate — and it raises its own questions, which we answered in the piece on serving raw meat properly. The pork chop is written up separately. Our Haji Lane sibling also runs a wasabi mayo, on the jujeh chicken wings.

The thing we are not going to claim

Our menu prints the word “wasabi”. It does not say which kind, and neither does our website.

So we are not going to tell you on a blog what the kitchen has not said on the menu. We would rather flag that plainly than have you take a claim from us that we cannot point at a source for — which is the same position we take about the fuel in our own grill, and for the same reason. If that changes, it will change on the menu first.

What we will say is that the distinction in this post is worth carrying around. If you are eating something that has been grated in front of you, you are eating a reaction that started seconds ago. If you are eating something out of a tube, you are eating horseradish and colouring, and it is fine, and it is not the same plant.

The same “what is this actually made of” question is worth asking of the beige paste on the other half of our menu — tahini — and of the garlic sauce that carries our Lebanese charcoal chicken.

Sources

The botanical name and family, the rhizome-versus-root characterisation, the substitute’s composition and labelling, the allyl isothiocyanate and myrosinase mechanism, the sharkskin and oroshigane graters, the degradation note, the non-oil-based comparison with capsaicin, the cultivation temperatures, the named growing regions and the between-fish-and-rice placement are all from Wikipedia’s article on wasabi, read on 10 September 2026. Our two menu lines were re-extracted from the live food-menu PDF the same day and are quoted exactly as printed.

If the rest of the Japanese vocabulary on our card is doing this to you, the dish guide beyond sushi is the wider version, the roe guide sorts out the three orange things, and the dips get told apart here. The full map is our guide to Japanese food in Singapore.

We are at 29 Hamilton Road, Singapore 209198, in Jalan Besar — Tuesday to Sunday 5pm to 11pm, brunch Saturday and Sunday 11am to 2.30pm. We serve pork and alcohol and are not halal. See the room, or book a table.