Tag Archives: allyl isothiocyanate

The Wasabi Kick

The freshly grated wasabi hides a secret known as the Wasabi Kick which produces a zingy heat when consumed with your favourite food. This pale green grated powder is known as Japanese horseradish, but this is not the same as the horseradish which complements your roast dinner. It is a distant cousin and is formally known as Wasabia japonica – a member of the Brassicaceae family. Wasabi is closely related to cabbage, cauliflower, broccoli and mustard.

Wasabi is cultivated in Japan alongside mountain stream beds enabling the production of a vast carpet of unique plants. They are long-stemmed with heart-shaped leaves and white flowers which branch from a knotted, thick, swollen stem, known as a rhizome.

The two main methods of growing wasabi involve the usage of semi-aquatic conditions to produce the sawa type (grown in water) and in fields to give oka wasabi (grown in soil). Usually, under sawa conditions larger rhizomes are formed than in oka grown wasabi. However, both give that extraordinary wasabi kick.

The wasabi plant is tough to cultivate and it flourishes best in mountain stream water.  At Wasabi Crop, we have developed expertise through continuous chemistry to generate wasabi rhizomes, leaves and stems for all our customers.

Real wasabi is expensive to cultivate and the majority is consumed in Japan: this is the major reason why most people have not tasted real wasabi. Most wasabi sold in supermarkets, sushi bars and restaurants is fake.  This fake wasabi usually consists of horseradish, mustard, starch and green food colouring.

Can you tell the difference between true wasabi and fake wasabi?

Yes, you can!

In most cases, when wasabi is ordered with your food, a squirt of ‘bright’ green toothpaste-like material is placed on your plate – and the customer is under an illusion because it is almost certainly fake wasabi!

Fake Wasabi

Fake Wasabi

Genuine wasabi is grated in front of the customer to produce the wasabi powder.  The best grater to use is the sharkskin paddle because it can finely grate the rhizomes. This grating process initiates chemical reactions through the mechanical damage of the cells inside the rhizome producing volatile compounds, rich in flavour.

Real Wasabi

Real Wasabi

The heat usually produced lasts for about 20 minutes and this is usually enough time to experience the wasabi kick.  This event does not happen with horseradish – which can retain its potency and sharp flavour for many days. The chemistry of horseradish and wasabi are similar but each have different amounts of naturally flavoured compounds to each their individual, unique flavour profile.  The central component in horseradish and wasabi rhizomes are glucose sulphur-containing organic compounds known as thio-glucosides.

During the grating and maceration of the rhizome, the cell walls break releasing the thio-glucosides and the enzyme called myrosinase.

What is the role of myrosinase?

Essentially, the main function of myrosinase is to break down the thioglucosides into glucose and by a chemical rearrangement called the Lossen Rearrangement generating varying amounts of isothiocyanate compounds.

So, during this process, the horseradish and wasabi will both produce different concentrations of the isothiocyanates.  Interestingly, horseradish generates about 10% less of the total isothiocyanates per kilogram of horseradish compared to wasabi.

The major isothiocyanate compound present in wasabi is called allyl isothiocyanate and this association is REAL WASABI producing a pungent zingy wasabi kick.  Another component is called 2-phenylethyl isothiocyanate and this is surprisingly found in horseradish. Other compounds include 6-methylthiohexyl isothiocyanate, 7-methylthioheptyl isothiocyanate and 8-methylthiooctyl isothiocyanate.

Studies have shown that isothiocyanates inhibit microbe growth and provide great benefits for preserving food against spoilage and suppressing oral bacterial growth.

More on allyl isothiocyanate!

The allyl isothiocyanate is responsible for the wasabi kick generating heat when consumed and this is different from that produced by chillies and peppers.

wasabi kick

wasabi kick chemistry

Hot peppers contain the compound capsaicin which stimulates the tongue. The heat created on the tongue can only be removed with oil based foods.  The experience that you will obtain from wasabi in your mouth is that of allyl isothiocyanate volatile vapours stimulating the nasal passages and this simply does not take place with capsaicin-containing foods.

In summary, the wasabi experience is related to the amount of allyl thiocyanate consumed. So, eat and enjoy plenty of freshly grated wasabi. The only solution if you can not manage the wasabi kick is just to control it with the consumption of food and/or beverages.

Real wasabi is expensive and the majority of it is consumed in Japan – here at Wasabi Crop we will give you the opportunity to buy wasabi varieties and let’s not forget the delicious leaves and stems for your stir fries and salads.

Enjoy your fresh wasabi – providing new foods for your table!

Sofia Kitson

Wasabi Crop Blog

Grating Fresh Wasabi Rhizomes


The secret of enjoying fresh wasabi lies in the grating of the rhizome to release the pungent zingy flavour. Fresh wasabi rhizomes are a rare and precious culinary commodity prized by sushi dining chefs. The best grater to use is the traditional Japanese ‘Samegawa-Oroshi’-Sharkskin Grater but these are quite expensive to purchase. However, you don’t have to worry as you can always use any fine grater available.

So, to begin the grating process you first wash the rhizome in cold running water and lightly trim off only the black bumps on the surface. This blackness is a result of a natural process due to air oxidation taking place at the surface of the rhizome.  Carefully, peel off the outer thin black layer on the rhizome, (if any) you find by using a potato peeler or something similar. Then begin grating from the thicker side a this section is fresher and yields a more zingy taste to give that beautiful pale green coloured wasabi paste.The freshly grated wasabi paste should not be stored in a metallic container, it is best to use an unsealed ceramic basin. During the grating process, a pinch of sugar can be placed on the grater to give the wasabi a milder flavour.
The remaining rhizome can be preserved for at least one month in a refrigerator by wrapping it up in a damp towel. Remember to replace the cloth every 2-3 days to keep the rhizome in good condition. If wanted, the whole rhizome can be grated all at once to produce small parcels of wasabi paste wrapped in ‘cling film’ and stored in the freezer until required.
Wasabi Japan

Freshly grated wasabi on a traditional Japanese Sharkshin

It is better to start grating the rhizome from its top end by swirling around the whole root to produce the best aroma and pungency as each part of the rhizome has slightly a different flavour profile and associated pungency. This approach will maximise the blend of the whole root. Once grated, the wasabi must be kept chilled in a refrigerator to preserve its pungency which dissipates within two hours or at room temperature the pungency will completely disappear in the space of 15 minutes. 

The wasabi rhizome should be maintained in a chilled state and not frozen otherwise its fibre will be damaged. If wishing to keep the grated wasabi paste for longer than one week, then the colour will darken and its pungency and smell will change due to the air oxidation of allyl isothiocyanate. It is better to grate the rhizome as and when required to eat immediately.

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Enjoy your fresh wasabi – providing new foods for your table!

Sofia Kitson

Wasabi Crop