Wasabia Japonica

Wasabi ワサビ (Wasabia japonica) is the 'King of Herbs' and only indigenous to Japan. The Honzo-wamyo (Japanese Names of Living Things) is a collection of 18 volumes of 1,025 types of plants including animals and minerals. This encyclopedia was written in the year 918 by Fukane Sukehito in the Heian period (794-1185) and describes wasabi as a medicinal plant which at the time was known as wild ginger. Wasabi cultivation in Japan has continued for over a thousand years.

During the Keicho period (1596-1615), the majority of wasabi cultivation was carried out on the Abe River in Shizuoka prefecture in central Japan. During this time wasabi was entirely consumed by the Japanese higher class and was governed by the Shogun Tokugawa Ieyasu (1543-1616). The distribution of wasabi in Japan ranges from Sakhalin Island, a large Russian island in the North Pacific Ocean to the most northerly region of Japan called Hokkaido and extending to Kyushu. 

The area of Japan which produces the highest yields of wasabi rhizomes is the Shimane prefecture.  Outside Japan, wasabi rhizomes are grown in New Zealand, Iceland, Taiwan, Korea, Israel, Brazil, Thailand, Columbia, Canada, USA, England and Northern Ireland.

Wasabi is a member of the Brassicaceae (Cruciferae) family of crops and mainly consists of brussels sprouts, broccoli, cauliflower, cabbage, watercress, bok choy, horseradish and the seeds of black mustard

Wasabi Varieties

During the two year growth cycle of wasabi a swollen stem known as a rhizome will be produced. The rhizome connects to several petioles producing deep green heart shaped leaves and these contain some of the pungent taste associated with wasabi. Today, Japan produces several types of rhizomes and they include Midori, Sanpoo, Takai, Shimane, Izawa, Medeka, Mazuma and Daruma. These wasabi varieties are a product from the Shizuoka and Shimane prefectures including Nagano Japan. In addition Hangen wasabi is cultivated from the Kanagawa prefecture. 

Wasabi Chemistry

The pungent taste of wasabi is the result of volatile naturally occurring organosulphur compounds called isothiocyanates (ITCs). These volatile ITCs are released when the plant tissues undergo mechanical damage resuting from cutting, grating and mastication. Subsequently, ITCs are not present in the plant but are a product from Sinigrin (glucosinolates) present within the cell vacuoles of all Brassicaceae plants.

When sinigrin-containing plant tissue is crushed or damaged, the enzyme myrosinase degrades sinigrin to produce allyl isothiocyanate (AITC), which is responsible for the pungent taste of wasabi. Sinigrin is also known to be allelopathic. However, myrosinase is a member of the glycoside hydrolase family and is the only enzyme that occurs in nature which as the ability to cleave a thio-linked glucose. The biological function of this enzyme is to catalyze the hydrolysis of a class of compounds called glucosinolates.

Consequently, the mechanical disruption of the plant tissues releases myrosinases from the cell wall and in the presence of water hydrolyses the glucosinolates to produce glucose and an aglucone. The aglucone is unstable and rearranges to produce sulphate and several other products. The ITCs are produced from Sinigrin under neutral and alkaline conditions.  The allyl isothiocyanate (AITC) has the main effect on the overall taste of wasabi due to high concentrations found in the rhizome part of the plant.  However, 6-methylthiohexyl-ITC and 7-methylthioheptyl-ITC both contribute to the characteristic fresh greenish flavour of wasabi. A combination of ITCs are present in different amounts and each has the ability to contribute to the overall wasabi kick.

Wasabi kick

The wasabi receptors are predominant in the nasal passages.  They are known as TRPA1 which belong to a group of receptors called the transient receptor potential (TRP) ion channels. TRPA1 is a cousin of TRV1 and is referred to as the capsaicin receptor. The role of capsaicin TRV1 receptors is to respond to exothermic heat generated from hot chilli peppers. These wasabia TRPA1 receptors have a more diverse scope than capsaicin receptors especially in the range of pungent foods. So, freshly grated wasabi releases volatile allyl isocyanates up the nose causing an activation of the TRPA1 to give The Wasabi Kick.  Remember wasabi and horseradish are not the same and give a different taste profile. Horseradish contains 2-phenylethyl isothiocyanate and this compound is not present in wasabia.

The wasabi kick is the result of a short reaction time between the myrosinase acting on sinigrin to give aglycone. The aglycone undergoes a Lossen rearrangement to give the amount of volatile allyl isothiocyanate (AITC) in the mouth. After 20 minutes the wasabi kick starts to diminish at room temperature due to the deactivation of myrosinase enzymes in wasabi. To partly revive the kick reactivate the myrosinase enzymes in wasabi using lemon juice.

Medicinal Properties of Wasabi

The research into the various isothiocyanates (AITCs) present in wasabi have indicated potential medicinal properties in certain disease states including application in cancer research. In addition, ITCs have demonstrated anticoagulant properties and may have applications in reducing heart attacks. The allyl-ITCs have indicated anti-asthmatic effects and may play a role in the pathogenesis of bronchial asthma due to the inhibition of inflammatory processes. Wasabi has had a long association with sushi due to the anti-bacterial properties to limit food poisoning and limiting the spread of Escherichia coli and Staphylococcus aureus.  In addition, wasabi can neutralise fish odour during food preparation. Wasabi continues to play an important role in Japanese culture and especially in food, medicine and its associated antibacterial properties.

Disclaimer

The information presented on this website is not intended to be used in conjunction to prescribe or to give any medical advice regarding the diagnosis of disease states. Wasabi facts and health benefits