Fresh Wasabi vs. Wasabi Paste: The Grated Rhizome and the Horseradish Tube Compared

That tube of wasabi paste probably isn’t wasabi. Most of it is European horseradish, mustard and green coloring, whether it comes from a tube or gets mixed from powder. Real wasabi is the rhizome of Eutrema japonicum, grated just before you eat it, and in the US it can cost as much as $100 a pound.¹ Both get their heat from the same kind of compound, which is why the imitation works at all. The differences are flavor balance, how fast the heat fades, texture and price.

Side by side

What’s actually in the tube

Most of what’s sold as wasabi outside Japan is horseradish, and the wasabi paste of Western restaurants is commonly made from it. Chowhound reports that the vast majority of commercial wasabi is European horseradish mixed with mustard and citric acid and colored green, and cites The Washington Post for an estimate that about 99% of the wasabi sold in North America isn’t real wasabi.¹ The Embassy of Japan’s magazine says some restaurants in Japan also use a cheaper mix of horseradish, mustard and food coloring.⁷

Labels show the range. The S&B tube above lists horseradish first and wasabi sixth, at 4.5%.² A foodservice wasabi powder in the same product database lists horseradish, mustard flour, tapioca starch, ascorbic acid and two synthetic colors, E102 and E133, and no wasabi at all.⁸ The front of a tube tells you little; read the ingredient list.

The paste is thicker and smoother than fresh-grated wasabi, and the S&B ingredient list shows why: potato starch, dextrin and a thickener (E415) alongside the horseradish.² Freshly grated rhizome is moister and a little coarse.

Same heat, different mix

Wasabi, horseradish and mustard make their heat the same way. Isothiocyanates are released when the plant’s cells are broken by cutting or grating. Allyl isothiocyanate is what gives horseradish its distinctive flavor, and related compounds turn up in mustard.⁴ In a Lincoln University (New Zealand) doctoral study of seven isothiocyanates in New Zealand-grown wasabi, allyl isothiocyanate made up 86% to 94% of the total. The overall mix differs, though: the same study found 2-phenylethyl isothiocyanate only in European horseradish.³ That’s a measured chemical difference. Nobody we found has tested how it changes the taste.

Which one is hotter? The sources disagree

You’ll often read that fresh wasabi is milder than paste. The two sources we found that describe the difference point in opposite directions, and neither one measured it.

We found no measurement of pungency across fresh wasabi, tube paste and prepared horseradish. The heat in any of them also depends on how recently it was grated or mixed (more on that below), so there may not be a single answer.

Why fresh wasabi is grated at the last minute

Fresh wasabi paste loses its pungency when it’s exposed to air, which is why the rhizome is grated just before serving, traditionally on a sharkskin or wooden grater. Chowhound puts the loss of flavor at about 15 minutes after grating.¹ The heat doesn’t vanish the second you grate it, but it fades fast.

Horseradish-based paste fades too. America’s Test Kitchen found that grated horseradish gets milder over time, and that vinegar keeps its heat by slowing the reaction; homemade prepared horseradish keeps its heat for up to two weeks in the fridge, by ATK’s account.⁵ The S&B tube lists brewing vinegar and an acid (E330).² We found no published figure for how long an opened tube stays hot.

Storing the rhizome. The Lincoln University study found that keeping rhizomes frozen at −10°C or colder for two months preserved their original levels of heat compounds.³

Why fresh wasabi costs so much

Chowhound puts genuine wasabi at up to $100 a pound in the US, against $3 to $5 for horseradish, about one-twentieth the price. Blame the growing. Wasabi’s specific growing needs limit where it can be cultivated. Chowhound says the plant needs a cool spot with its roots in clear running water and takes two years to harvest, against 140 to 160 days for horseradish.¹ The Embassy of Japan’s magazine says a rhizome can take up to three years to reach harvest size.⁷ Those figures describe different growers, so they don’t have to agree.

Wasabi isn’t confined to Nagano Prefecture, whatever you may have heard. Shizuoka Prefecture says it had Japan’s highest production volume of water wasabi rhizomes in 2022.⁶ Outside Japan, the main places it’s been grown successfully are China, Taiwan, Australia and New Zealand.

Can one stand in for the other?

Yes, and paste usually does. These are starting points; for more options, see wasabi substitutes.

Where these come from. The “smaller dab” follows Chowhound’s description of commercial paste as much harsher than fresh;¹ Tasting Table’s view that wasabi is more intense than horseradish points the other way,⁹ so taste before you add more. The powder instruction applies to one product only.⁸

When to use which

The Embassy of Japan’s magazine says wasabi is mainly paired with sushi and sashimi, where it removes fishy smells and brings out the fresh flavor of seafood.⁷ Fresh wasabi is worth the price where you can actually notice its sweetness and short-lived heat: good sashimi, nigiri and simple raw fish. Tube paste makes sense for everyday sushi, dressings, dips and anything where wasabi is one flavor among several. For cooking ideas, see cooking with wasabi.

What isn’t known

• We found no measured comparison of pungency between fresh wasabi and commercial paste.
• No published figure for how long an opened tube of paste keeps its heat.
• No source tested how 2-phenylethyl isothiocyanate changes the taste of horseradish-based paste.
• We didn’t survey how much wasabi other brands’ pastes contain; the S&B tube is one example.

Related

• Wasabi and horseradish, the full profiles
• Wasabi substitutes and horseradish substitutes
• Wasabi powder vs. paste and wasabi vs. horseradish
• Too much wasabi? and cooking with wasabi
• Mustard powder and Japanese spices