A Guide to Fresh Wasabi

Did you know that a lot of the time the fiery, nose-wince-inducing, slightly-eye-watering wasabi that you eat with your sushi doesn’t actually contain much wasabi? The wasabi powders and pastes that you buy in the shops or which are used in many restaurants are usually a combination of mustard, horseradish, green food colouring and just a hint of wasabi, probably from the stem or leaves. Eating fresh wasabi is a completely different experience. And how hot is wasabi?

Growing Fresh Wasabi

Wasabi as a plant is similar to horseradish in that both belong to the Brassica family (which is quite a broad family as it also contains vegetables such as cabbage, broccoli and kale) and both have a fiery pungency but they are different species and offer very different flavours.

Horseradish is really easy to grow in the UK. It’s like a weed and grows rapidly in the wild. We regularly see horseradish growing by the roadside or in parks. (We would like to forage for it but although we could pick the leaves it’s against the law to dig up roots on land you don’t own.) It’s the long white root that provides the flavour. Wasabia Japonica’s flavour comes from its rhizome, which is kind of like a swollen stem.

Traditionally wasabi grows next to crystal clear gravelly mountain streams in rural Japan (a delightfully romantic image) but it is actually possible to grow wasabi in the UK (although our garden is significantly less romantic than a beautiful mountain region). Water grown wasabi is known as sawa- or mizu-wasabi, soil grown is known as hatake-wasabi.

Our soil grown wasabi needs a little love. It likes relatively cool conditions and much prefers the shade to the sunshine. We once had to move our wasabi into a sunny spot temporarily and it wilted like the Wicked Witch of the West. (It recovered 24 hours later when it was back in the shade.) It also needs to be well watered, although it doesn’t like to sit in water. A cool, rainy British summer is ideal. We grow it in pots close to the north facing wall of our house. It takes a while for the rhizome to grow – you need to be patient for a couple of years – but the result is worth it. The cat was very impressed with our attempts.

Eating Fresh Wasabi

The first time we ate fresh wasabi, it was a revelation. It did have that amazing familiar pungency but it also has a sweetness that you don’t expect.  One of the advantages of growing wasabi is that the other parts of the plant are all edible: the lovely heart shaped leaves can be used as a garnish (and eaten), the stems chopped up like herbs and even the delicate flowers, which are especially good in a tempura. The other parts are much more mild and, while they impart flavour, don’t have the pungency of the rhizome.

How To Prepare Fresh Wasabi

Wasabi rhizomes can grow up to 100g in size, although some can be bigger. You would have to have a big sushi party to get through that amount but it is possible to store it.

The pungency of the wasabi fades when it is exposed to air, so it is best to grate it just before serving. There are various graters you can buy. Traditionally, a shark skin grater is used, although it is usually made from a type of ray. Purists prefer this, claiming that this is the one that ensures that the wasabi has the best creamy consistency and brings out the best flavour. But you can also get other types, including a metallic grater or, our preference, a ceramic grater.

Using a vegetable peeler, we just scrape off a small amount of the rhizome’s outer layer, up to the length we wish to grate, then grate the wasabi in a circular motion.

One useful little implement is a bamboo brush which you can use to gather up the grated wasabi. The stiff bristles are much more efficient at negotiating the grater’s bumps than our fingers. Gather the grated wasabi up into a nice little ball and serve. It’s worth grating slightly less than you think you will need – you can always grate more.

Storing Wasabi

A fresh rhizome will store well in the fridge for a couple of weeks. We tend to keep it wrapped in damp kitchen paper and grate as much as we need. If we don’t get through an entire rhizome in that time, it tends to go a bit black, so the best thing to do is freeze it. The whole rhizome doesn’t freeze well but grated wasabi freezes brilliantly.

We tend to grate into portions and then store inside little plastic tubs – the sort you get sauces/dips in with a takeaway meal. Then we seal – in order to minimise exposure to the air and pop into the freezer. Take them out when you need them. The portions thaw in no time at all. Alternatively, you can wrap the grated wasabi into parcels of clingfilm.

So How Hot Is Wasabi?

Unlike chillies, which have the Scoville scale to measure their heat level, wasabi heat doesn’t really have a similar measurement system. The Scoville scale is based on dilution of the chemical capsaicin – how much water it takes before you can no longer detect the heat of the chilli. But wasabi is a root not a pepper and instead of releasing capsaicin, it contains allyl isothiocyanate, a compound which is also found in mustard, radish and horseradish. Its pungency is a result of its volatility – the gas it releases feels as though it goes straight up your nose rather than remaining on your tongue like the capsaicin of chilli.

People’s reactions to wasabi will differ quite widely. Some people can scoff the hottest of chillies but can’t take the heat of wasabi. But it is undoubtedly hot! Fresh wasabi has a milder pungency than the horseradish/mustard/green paste.

How To Eat Wasabi With Sushi

Wasabi and sushi go together like fish & chips, salt & pepper and gin & tonic. Wasabi was originally used with sushi in the Edo period in Japan and was thought not only to help mask any smells from the fish it was also considered to have properties that help prevent the growth of bacteria.

The best way to eat wasabi with sushi is to mix it with a small amount of soy sauce in a little dish. Never dip the rice part into the dish – the rice will soak up the soy sauce and all you’ll get is a mouthful of nose-wincing salt, losing the delicate flavour of the fish. Instead, turn the sushi upside down and dip the fish side into the sauce. (It’s absolutely fine to eat sushi with your fingers.) If you are having an omakase meal, where the chef prepares the sushi for you, it is likely that they will add exactly the correct amount of sauce and wasabi, so you won’t need to worry.

We love making chirashizushi – a bowl of seasoned rice with a layer of seafood atop – which we serve with our own fresh wasabi and garnished with the lovely heart-shaped wasabi leaves.

Related Posts You May Enjoy

• 
  Planning a Trip to Japan
• 
  The Makanai: Cooking for the Maiko House
• 
  Setsubun Food – Bean Throwing Day
• 
  The Gassho Farmhouses of Rural Japan
• 
  Recipe: Japanese Simmered Pork Belly – Buta no Kakuni
• 
  RECIPE: How to Make Umeboshi
• 
  Osaka Restaurants Japan – Kuidaore on Dotonbori
• 
  RECIPE: Japanese Fried Chicken Karaage
• 
  Visit Yakushima Island in Japan

• 
  Zero Waste Recipes Before Your Holiday
• 
  RECIPE: Vegetable Biryani Tamil Nadu Style
• 
  RECIPE: Vegan Wild Garlic Pesto
• 
  Recipe: Venetian Pasta Sauce
• 
  RECIPE: Biryani Raita Recipe
• 
  RECIPE: How to Make Costa Rica’s Gallo Pinto
• 
  Recipe: Japanese Simmered Pork Belly – Buta no Kakuni
• 
  RECIPE: How to Make Umeboshi
• 
  Recipe: Shopska Salad