The Past, Present and Future of the Wasabia japonica (Japanese Horseradish) Industry
Compiled by The Wasabi Reviewer & edited by The Wasabi Maestro
Wasabi, Japanese Horseradish (Wasabia japonica) is a perennial plant native to Japan, although China is now also claiming it as a native. It has been cultivated in Japan for more than a thousand years and is now being grown in a number of other countries including New Zealand, China, Vietnam, Canada, and Australia as interest in Japanese cuisine expands, and the health benefits of consuming Wasabia japonica become better known.
Wasabia japonica can be grown in a number of ways, in water (Sawa wasabi) or in soil (Oka wasabi). The unique flavour of Wasabia japonica comes from isothiocyanates (ITCs) which are produced by the action of water on a mixture of precursor Glucosinolates and the enzyme myrosinase when the tissue is disrupted. ITCs found in Wasabia japonica are volatile, possess strong pungent smells and are toxic at very high intakes [Allyl ITC is the infamous Mustard Gas of WWI]. The overall flavour of Wasabi japonica depends on the mixture of individual ITCs. Allyl ITC is found in the highest concentration in all tissues, ranging from 86-92% of the total ITC content. Apart from flavouring sauces and foods, the three unique Wasabia japonica Isothiocyanates (ITCs) have significant anticancer effects. ITCs can also counter inflammatory conditions like asthma and anaphylaxis. ITCs have also been shown to inhibit platelet aggregation in the blood.
Wasabia japonica is a valuable crop that can be processed into a tasty condiment, and as a useful dietary supplement. Its production and consumption will increase as it becomes more appreciated in Western cuisine and health circles.
Wasabia japonica, known as Japanese Horseradish (Wasabia japonica) is a native condiment crop of Japan. It is not known when Wasabia japonica was first brought into cultivation but Japanese historical records indicate that Wasabia japonica, known originally as wild ginger, was introduced as a medicinal plant by Sukahito Fukae. The first Japanese medical encyclopaedia called “Honzo-wamyo” was published in A.D. 918 and it states that “wild ginger” (Wasabia japonica) had been grown in Japan for at least a thousand years (1). During 1596-1615 A.D. Wasabia japonica cultivation began on the upper reaches of the Abe River in Shizuoka prefecture. Its use, however, was restricted to the ruling class by order of the Shogun Iieyasu Tokugawa (2). At present, the natural distribution of Wasabia japonica in Japan ranges from Russia’s Sakhalin island, north of Hokkaido (the most northern Japanese island) to Kyushu (the southernmost major Japanese island) (3). However, the Shimane region is the largest area of Wasabia japonica production and breeding research in Japan at present.
Wasabia japonica is now being grown in many countries in the world including New Zealand, Taiwan, Korea, Israel, Brazil, Thailand, Canada and USA. In New Zealand, the Ministry of Agriculture and Fisheries introduced Wasabia japonica for experimental cultivation in 1982 (4). Agronomic investigation of this crop was stimulated by commercial interest in 1986 (5,6). New Zealand Wasabi Limited started commercial development of a hydroponic growing system for wasabi in 1990, with their first commercial sales in 1994. This company has now grown into the largest supplier of Sawa (water grown) wasabi in the Southern hemisphere (49). The majority of their products are used in Nutraceutical products due to its high level of active constituents. Preliminary assessment of the growth and plant yield of soil-grown Wasabi japonica was carried out at Lincoln in 1995 (7). Yields of flavour compounds, as affected by fertilizer treatment, were carried out in 1997 (8, 9). Further research has been performed at Lincoln University to develop an understanding of Wasabia japonica growing in New Zealand, especially the agronomy, cultivation methods, ITC variation and stability (10).
Botany of wasabi
Wasabia japonica is a member of the Cruciferae family which also includes cabbage, cauliflower, broccoli, sprouts, water cress, radish, mustard and horseradish. The European horseradish (Armoracia rusticana) is a distant cousin of Wasabia japonica and is often coloured and mixed with mustard and other ingredients to produce a “fake” wasabi (50). The genus Wasabia consists of two species, Wasabia tenuis (an uncultivated species) and Wasabia japonica (the cultivated species). These two species are distinguished primarily by their cytology, stem size, colour, leaf size and shape (3).
Wasabia japonica is a glabrous, perennial herb that grows about 450 mm high, producing leaves on long petioles from the crown of the plant. As the plant ages the rhizomes start to form and, at maturity after 18 months, the Wasabia japonica plant has a distinctive thickened stem (or rhizome) connected to the heart shaped leaves by long, thin petioles (Figure 1).
Rhizomes are the most favoured plant part of Wasabia japonica. Dependent upon the variety, the plants have one or more main rhizomes and can have a number of secondary stems (7).
The lengths and weights of rhizomes vary widely between variety e.g. for Daruma – the single rhizome length ranges from 50 to 200 mm long and weighs 4 to 120gm. [New Zealand Wasabi has exhibited Daruma rhizomes over 600mm long and weighing 1.2 Kg at a number of International Trade Shows]. Wasabia japonica leaves are simple, cordate-reniform, undulate-toothed and 80-250 mm in diameter. Petioles are vertical to oblique, 300–500 mm long, basally flattened and surround the rhizome. Whole fresh plants can weigh up to 3.4 kg (3).
Wasabia japonica flowers are white, bracteate, arranged on racemes, with ascending sepal, cruciform and obovate petals, perfect septum, elongate styles and simple stigma (3). Fertilisation is mainly by cross pollination, and insects. Seeds must be stored in a cool moist environment, since dry storage will result in desiccation and loss of viability of the seed. Fresh seed is naturally dormant until it is vernalised by storing at a low temperature (5). Fresh seed is notoriously difficult to germinate, and methods are closely guarded by growers.
Wasabia japonica cultivars
In Japan a cultivar is usually named after its region of cultivation and, thus, Wasabia japonica cultivars are considered regionally specific in Japan. Seventeen Wasabia japonica cultivars have been developed and each has a strict cultivation and climate requirement that limits major cultivation to distinct areas (3). Specific regions and individual farmers produce their own unique cultivars as a result of persistent inbreeding and selection. According to some Japanese farmers Wasabia japonica has eight well-known cultivars which are Mazuma, Daruma, Takai, Shimane, Midori, Sanpoo, Izawa Daruma and Medeka. These cultivars were developed in the Shizuoka and Shimane prefectures. Another important cultivar ‘Hangen’ comes from the Kanagawa prefecture.
Daruma is the most popular variety, known to grow well under marginal environmental conditions, such as warmer temperatures. It was developed by plant breeders based in the Shimane Research Station. This variety produces a single rhizome and can be stored longer than most of the other varieties. It also contains a lower amount of ITCs and is used mainly as a table vegetable, being freshly grated when required. A large amount is also used for processing purposes.
For poor quality locations the Shimane Wasabi Research Station developed Fuji Daruma, Izawa Daruma, Ozawa Daruma and Sanpoo in Shimane. However, all Shimane cultivars produce high quality rhizomes. Mazuma was developed in Shizuoka (but was originally grown in Wakayama and Okutama) and overseas research suggests that it has more heat tolerance than the Daruma cultivars although no published data can be found to verify this. In New Zealand, Daruma is the main commercial cultivar of Wasabia japonica.
New Zealand Wasabi has trialled all available varieties in their hydroponic operations and selected the best variety for their own use.
Cultivation of Wasabi japonica
In Japan, Wasabia japonica sometimes grows naturally in the gravel beds of mountain streams and is highly adapted to this environment. For commercial Wasabia japonica growing two types of cultivation methods are used. These are soil grown wasabi (Oka) and water grown wasabi (Sawa). Japanese growers select the method depending on where they live and the particular end use of the plants after harvest. Most wasabi farms are kept in the family and the last wasabi bed was reputed to be built alongside a mountain stream some 200 years ago. Due to the effects of acid rain and the weather in the mountains of Japan, a number of family farms are now being abandoned as younger members of the family immigrate to the cities.
Wasabia japonica plants grown in the soil require large amounts of organic fertiliser added to the soil before planting, and also require ongoing herbicides and pesticides used to maintain the health of the plants. Being a member of the cabbage family it is susceptible to the diseases of that family. The ground also needs to be kept damp at all times as the plant is regarded as semi-aquatic in its growth characteristics. It is regarded as good practice that the growing plot be abandoned after three harvests and not returned to for at least ten years.
If Wasabi japonica is grown in running water then less fertilisation needs to be used, although it is known that some Japanese and Chinese farmers will put sacks of chicken manure or blood and bone upstream from their farms to make the wasabi grow faster. Less pesticides and herbicides are used with this growing method, although the environmental impact is just as great.
All parts of the plant can be used for a number of products. The rhizome is the preferred part of the plant as it has the most active ingredients, but the petiole, roots and leaves are also used.
Most of the plant is used in food products, although now more and more of the rhizome is being used for Nutraceutical purposes. This was not the case in 1993 when the rhizome only was used for food products (3). The leaf and stem were pickled and only available in Japan.
The general concensus is that water grown Wasabia japonica (Sawa) produces larger rhizomes with more active ingredients, and for that reason is highly sought after and, therefore, command higher prices.
Soil-grown Wasabi japonica
Wasabia japonica requires specific environmental conditions to thrive. Soil-grown wasabi requires an air temperature from 6-20°C with 8-18°C considered optimal. Soils containing well rotted organic material with a pH 6-7 are considered best. It is most often grown on well-drained soil under mulberry or plum trees in Japan, whereas in New Zealand and China soil-grown Wasabia japonica is usually grown in shade houses rather than under trees.
Water grown Wasabia japonica
Water grown Wasabia japonica requires air temperatures ranging from 8-18°C. However, a narrower range of temperatures (12-15°C) is considered ideal. An air temperature of less than 8°C inhibits plant growth and at less than 5°C plant growth ceases. Other environmental factors can have an effect on the growth of Wasabia japonica and need to be considered carefully e.g. light levels, stable water temperature, good nutrient supply, and well aerated, neutral or slightly acidic pH water containing a high dissolved oxygen level and a large supply of water to maintain consistent flow (this particularly depends upon the growing system being used).
Rainfall accumulation is also important, with an even distribution desirable to stabilize the water supply and temperature (3). Spring water is considered best because of its clarity, stable temperatures and high level of oxygen. At warmer temperatures the dissolved oxygen in the water decreases, which inhibits the growth of plants.
Silty or muddy water is undesirable as it may contain insufficient oxygen, but some silt in the water is considered beneficial as a source of nutrients. In Japan, Wasabia japonica grows on the wet banks of cool mountain streams and springs in specially built growing beds. Overall, construction and establishment of a traditional growing bed is expensive and labour intensive.
Water grown Wasabia japonica is produced in 42 prefectures, and soil grown Wasabia japonica in 21, out of 47 prefectures in Japan, which indicates that flooded cultivation is popular and is considered to produce a high quality product.
The unique environmental requirements and shortage of cultivatable lands limit Wasabia japonica production areas to 880 hectares in Japan (11) and 400 hectares in Taiwan, but demand for Wasabia japonica condiments is spreading from Japanese cuisine to modern western food. The increasing interest in Wasabia japonica and the inability to expand production in Japan has seen prices rise steadily since 1970 (3). High prices have stimulated research into soil production methods and the investigation of production areas outside Japan. The Japanese have invested heavily in soil-grown wasabi farms in China.
In 1982, the cultivation of Wasabia japonica was trialled in New Zealand (6) because of New Zealand’s climate (appropriate air temperature range, high quality water, long sunlight hours), which meets the ideal requirements for growing quality Wasabia japonica outside Japan. However, the area of soil grown Wasabia japonica is increasing in Taiwan, China, Vietnam, Colombia, Canada, Korea, Thailand and USA. The expansion in soil-grown Wasabia japonica is mainly to reduce the high initial cost of water-grown wasabi establishment and associated high labour costs. Although long term the costs are consistent with each other, with a higher return being obtained for the Sawa Wasabia japonica, the better long term investment is in becoming a Sawa Wasabi Grower.
In 2010 the number of New Zealand growers has fallen to the point where there is one major grower, processor and marketer (49), with a few smaller growers growing under contract. The regulatory environment in New Zealand stifles the expansion of the industry there, even though the water growing systems developed lead the world (49). It is anticipated that within the next decade the New Zealand production of high quality wasabi will cease and the fledgling industry will vanish, although the technology is being licensed worldwide.
Uses of Wasabia japonica
Wasabia japonica adds a unique flavour, heat and greenish colour to foods and, thus, it is a highly valued plant in Japanese cuisine. Wasabia japonica is described as having ‘a sharp hot taste with a pungent smell’ but the heat component in Wasabia japonica is different from chillies, and the hotness quickly dissipates in the mouth leaving an extremely pleasant mild sweet vegetable taste, with no burning sensation at all. Wasabia japonica adds aesthetic and culinary appeal to many foods and is considered a staple condiment in the Japanese diet. Recently, it has found widespread appeal in western cuisine due to its ability to change an ordinary dish to an extra special one by improving the taste (with addition of a spicy flavour) and eye appeal i.e. by decorative contrast of the light green colour. As a result, it has become a new culinary flavour for the rest of the world.
All the plant parts of Wasabia japonica possess some flavour but vary in the sharpness they deliver (8,12) and are, therefore, used for different purposes. Basically, Wasabia japonica can be used in four ways. Three of these relate to food, and the fourth relates to health.The food uses are as a condiment on the side of a dish, as a spice or herb in a dish and as Wasabia japonica flavour in processed foods. Rhizomes are grated using a fine grater (such as sharkskin) to prepare fresh paste to be placed in a mound on a dish next to sliced raw fish (sashimi), spread on the raw fish in sushi preparations, or served on a small dish to accompany a bowl of cooked noodles (3). Sometimes grated Wasabia japonica is mixed with other ingredients like soya sauce and vinegar to prepare a dip for use with raw fish or other dishes, according to individuals’ choice. Tofu (soybean curd) is often decorated with grated Wasabia japonica.
Wasabia japonica petioles and leaves are pickled in sake brine or soya sauce and are popular accompaniments for white rice. Sometimes fresh leaves are used in salads and dried leaves are used to flavour cheese, salad dressings or crackers. Wasabi petioles and leaves are also used in cosmetics and for Nutraceutical use for various ailments.
A Wasabia japonica wine is sold in some Japanese specialty stores. A high alcohol content Wasabia japonica spirit was released in London in May 2010 to high acclaim. This product which was developed in New Zealand is now being sold in the European Union (51) and worldwide.
All grades and parts of the Wasabia japonica plant are commonly mixed with European horseradish (Armoracia rusticana) powder, mustard and food colour to produce ‘fake wasabi’ paste in tubes or to sell as fake wasabi powder. Around the world, a variety of genuine Wasabia japonica flavoured quality products e.g. sauces, pastes and mayonnaise have been developed to add to snacks and foods, as well as being sold in their own right.
Genuine Wasabia japonica products contain only Wasabia japonica and are not diluted with European horseradish, beet extracts or mustard. If possible avoid wasabi products that are highly coloured with artificial additives (either bright green, blue or yellow) as many of these products also contain other sources of taste which interfere with the clean taste of 100% Pure Wasabia japonica, and are known carcinogens. There are now a number of websites that review products that purport to be wasabi or contain wasabi (50, 52).
There is an interesting story of the arrival of wasabi into the Western diet on the http://www.worldwasabicouncil.com/info.html website.
Wasabi paste preparation using fresh wasabi rhizome
In traditional Japanese cuisine, Wasabia japonica is prepared by grating the fresh stem against a rough surface, such as a ginger grater, in much the same way as horseradish is prepared (3). The traditional method in Japan is to use sharkskin or “oroshi” as a tool for grating Wasabi japonica rhizome and is still regarded as the preferred method of obtaining the best flavour, texture and consistency in freshly ground Wasabia japonica.
Using a sharkskin grater and keeping the rhizome at a 90° angle to the grating surface is reported to minimize the volatiles’ exposure to the air. It is also stated that, in this way, the volatile compounds are allowed to develop with minimal dissipation.
In Japan and the rest of the world, wasabi paste is commercially prepared using mincers to finely grind the rhizomes and other parts of the plant, and then it is mixed with other ingredients depending on the end use of the paste (50).
Flavour constituents of Wasabia japonica
Isothiocyanates (ITCs) are a group of naturally occurring sulphur compounds responsible for the characteristic flavour of Wasabia japonica (13-15). The compounds are volatile in nature and are evolved from plant tissues when they are disrupted, e.g. in the preparation of food, grating, cutting, chewing etc.
However, plant tissues do not contain ITCs, but contain Glucosinolates which are the precursors of ITCs. Glucosinolates (GSL) are a group of glucosides, (i.e. they contain glucose in the structure), stored within the cell vacuoles of all Crucifereae plants (14).
Glucosinolates are a complex group of _-D thioglucose compounds synthesised from amino acids (8). They contain a sulphonic group which is usually bound to sodium or potassium, making then anionic (16, 17, 18). The sulphate in the sulphonic group is attached through a C=N bond and different side groups (R) give a wide range of related glucosinolates. Each one has its own characteristic odour or taste (Table 1). Due to the presence of the glucose in the molecule glucosinolates are hydrophilic, non volatile compounds (17).
When plant tissues are mechanically disrupted or injured (eg. by chewing, crushing or grating in the preparation of food or insect attack), the myrosinase is released from the cell wall and in the presence of adequate moisture, myrosinase rapidly hydrolyses the GSLs to yield glucose and a aglucone. Some of the intermediate steps have not been fully described (19, 20). The organic aglucone is unstable and undergoes Lossen Rearrangement (21) to produce sulphate and a variety of other products.
The nature of the products is dependent on the number of factors, including the structure of the GSL side chain, the reaction conditions (e.g. pH), the presence of cofactors (e.g. metal ions, specific proteins), temperature and duration as well as the age and condition of the plant tissues.
Isothiocyanates (ITCs) are formed from GSLs under neutral and alkaline conditions. However, GSLs that contain a _-hydroxyl group in their side chain, give rise to ITCs that spontaneously cyclize to form oxazolidinethiones. Some aromatic and heterocyclic GSLs produce ITCs which are unstable at pH 7 or higher and break down to release the corresponding alcohol and inorganic thiocyanate ions.
However, once formed, ITCs are more stable under acidic conditions. In weakly acidic pH or in the presence of Fe+2 and/or endogenous nitrile factor, nitriles are produced from aglucone by autolysis instead of ITC, with the liberation of elemental sulphur (20). The relative proportion of ITC to nitriles can vary widely depending upon the conditions of autolysis (20).
Thiocyanate formation is believed to involve a cofactor, which may also be a protein, since it has been shown to be labile to both heat and polar organic solvents. Most of the sulphur containing end products formed by the enzymatic and non-enzymatic reactions of GSLs are volatile (14).
Several ITCs have been reported from previous investigations into Wasabia japonica and each ITC has a specific flavour profile (8, 15) with the complete taste of Wasabia japonica being derived from the combined tastes and odours of all the ITCs present. A summary of different ITCs reported from previous investigations into the ITC content of Wasabia japonica tissue is listed in Table 1.
Allyl ITC has the main effect on the overall taste of Wasabia japonica because it is the ITC found in highest concentration in the rhizomes and other plant tissues (9). Allyl ITC is also found in the highest concentration in horseradish (12). While Allyl ITC is the main flavour component of Wasabia japonica due to its pungency, other ITCs, e.g. 6-methylthiohexyl ITC and 7-methylthioheptyl ITC, by giving their characteristic fresh greenish flavour, do contribute significantly to the total taste profile of Wasabia japonica (15, 24).
Medicinal properties of Isothiocyanates
The medicinal value of chemicals extracted from Wasabia japonica were first documented in the Japanese medicinal encyclopaedia during the 10th century (24). Recently, medical research interest in ITCs has become more intense because of their potential to have a wide variety of medicinal, pharmacological or industrial applications. These exciting applications are at an early stage of investigation, most likely because of Wasabia japonica’s high present commercial value and scarcity. Because of this scarcity and the fact that the useful ITCs are natural (and can’t therefore be patented), more effort is being put into trying to synthesize the ITCs for commercial gain instead of increasing the natural levels found in the wasabi plant.
An interesting use developed to date is the SaWasabi® Manuka Honey and Wasabi Soap that has been developed to assist those people suffering from psoriasis and similar skin problems. Originally, developed for a family member, it is now available over the Internet.
Medicinally, the most important feature of ITCs is evidence that they have a chemopreventive effect on cancer at a variety of organ sites including lung, mammary glands, liver, oesophagus, bladder, pancreas, colon and prostrate (25). A case-control study in Los Angeles (26) showed that high consumption of Cruciferae vegetables containing ITCs reduced the risk of developing colon cancer (27-31).
Tests have been carried out on tumours in rats and it has been reported that some ITCs have a protective role against breast, stomach and colon cancers in rats (32, 33). Several mechanisms have been proposed and investigated for tumour inhibition by ITCs, for instance Sulforaphane (SFN) and phenylethyl ITC (PEITC) are reported as potent inducers of the phase II enzymes involved in detoxification of carcinogens (34). The inhibition of chemically induced lung tumorigenesis by PEITC was mediated primarily by the inhibition of metabolism which resulted in a decrease in O methylguanine in lung DNA, indicating that ITC targets cytochrome P450s (35, 36). Results from recent bioassays in A/J mice appear to support the mechanism of induction of apoptosis in lung by PEITC and butyl ITC (BITC) (37). Extensive research on ITCs commonly found in cruciferous vegetables such as watercress, broccoli, radish and cabbage have been linked to the reduced risk of certain human cancers (27, 28).
While PEITC is not found in wasabi, the long chain methyl ITCs that are ONLY found in wasabi have been found to be 40 times more effective as anticancer agents (54, 55, 56, 57, 58) compared to the next best (Sulforaphane) which is found in broccoli and the use of which is controlled by John Hopkins University for commercial gain after the research was funded from the public purse.
From the chemoprevention point of view it is important to know whether the beneficial effects come, at least in part, from ITCs in the diet. In a cohort study it was clearly shown that individuals with detectable levels of ITCs in the urine were less likely to develop lung cancer (38). It has been suggested that normal dietary levels of ITCs derived from Wasabia japonica or other fresh cruciferous vegetables eaten regularly can protect against the low levels of carcinogens encountered in everyday life (25). As a result, the American Cancer Society recommends that cruciferous vegetables should be part of every person’s daily diet to reduce the risk of several cancers.
Effects of isothiocyanates on blood
The ITCs in Wasabia japonica have been tested for inhibition of platelet aggregation mediated by arachidonic acid (39), and for deaggregation. ITCs showed a ten times higher response than is reported for aspirin. In the case of heart attacks, where aspirin is commonly prescribed, ITCs have been shown to have a more rapid action at low levels than the thirty minutes for aspirin.
In this regard, the most potent ITCs reported are -methylthioalkyl ITCs, especially 6-methylthiohexyl followed by 7-methylthioheptyl and 5-methylthiopentyl ITCs. The anticoagulant property of ITCs could be used in the treatment of elderly people and during surgery where preventing platelet aggregation is vital for the well being of the patient. The mechanism by which the ITCs inhibit platelet aggregation from occurring has not been precisely determined but may be through a specific inhibition of the arachidonic acid cascade (40). This therefore raises the possibility of using ITCs to limit inflammation in tissues, as anecdotal evidence describes relief for arthritis sufferers.
Anti-asthmatic and anti-inflammatory properties
Benzyl and Allyl ITCs from onion extracts showed anti-asthmatic effects when studied by Dorsch et al. (41). Thromboxanes (generated by lung tissue and by aggregating platelets during lung anaphylaxis) and prostaglandins (generated by mast cells during activation) are known to cause bronchial obstruction and generally play a role in the pathogenesis of bronchial asthma.
The isothiocyanates prevented bronchial obstruction caused by subsequent inhalation of ovalbumin but did not prevent obstruction caused by inhalation of histamine acetylcholine. This indicates that the anti-asthmatic effect of ITCs are not due to an anti-histamine effect but act by inhibiting the inflammatory process at an earlier stage, possibly the production or action of other inflammatory molecules such as thromboxanes or prostaglandins. Thus, ITCs could potentially be used to counter inflammatory conditions such as asthma or even anaphylaxis.
Traditionally, horseradish and mustard have been used as a remedy for clogged sinuses, relief of congestion, muscular pain and inflamed joints (40).
There has been a great deal of work done on the ability of ITCs contained in Wasabia japonica to stimulate and assist the liver into detoxifying the body.
Unique compounds within Wasabia japonica induce Phase I and Phase II detoxification systems in the liver.These compounds have been found to be 40 times more effective than other similar compounds. Toxins acted upon by these systems are converted to more water-soluble forms, which the body eliminates through urine or stool.
A healthy liver is important to enjoy a healthy lifestyle. Wasabia japonica also exhibits antioxidant and free radical scavenging activities.
Coupled with a healthy liver you have the best means of enabling the natural defenses of the body to combat the toxins and other stresses imposed by today’s lifestyle. (53)
Masuda (42) has suggested that Wasabi japonica could contribute to a healthy smile by inhibiting the growth of the bacteria on teeth and gums in the mouth. Streptococcus mutans is known to cause dental caries and the consumption of Wasabia japonica can reduce bacterial activity. This was explained by Wasabia japonica’s ability to interfere with the sucrose-dependent adherence of cells to the surface of teeth and gums.
Nutraceutical grade 100% Pure Wasabia japonica powder complete with certificates of Analysis (both micro and active ingredient levels) is now available on a worldwide basis. It is expected that this use will overtake the food sector as the general public and medical practitioners realise the health benefits that consuming the true Wasabia japonica products can bring. (53)
Other industrial applications
ITCs extracted from Wasabia japonica can be used to make antibiotics, fungicides, insecticides, nematocides and as wood preservatives (43). ITCs are said to act as an antidote to food poisoning bacteria, one factor that has led to the use of Wasabia japonica with raw fish dishes in Japan (44-46). It is also reported that ITCs may have a role in protecting against diarrhoea (47).
ITCs have also been used as antifouling compounds to stop seaweed growing on ships’ hulls.
Recently it has been shown that Wasabia japonica contains anti-fungal metabolites that can render plants resistant to virulent isolates of the blackleg fungus (48). This fungus can devastate commercially important crops such as the oilseed plants rapeseed and canola. There is a potential to develop a natural fungicide using Wasabia japonica extracts.
Wasabia japonica is a valuable crop that can be made into a tasty condiment. In Japanese cuisine freshly ground Wasabia japonica is used to add a clean spicy flavour directly to foods. Wasabia japonica is also made into a paste which is stabilised by the addition of a number of other ingredients. In Western cuisine where hot spicy tastes are a recent addition to the diet, milder sauces and mayonnaises containing Wasabia japonica are more often appreciated. The problem arises in the fact that the consumer finds it difficult to tell the difference between true Wasabia japonica products and those made from the “fake wasabi” mixture of European horseradish, mustard, and artificial colours and flavours. Unless pressure can be brought to bear upon Government to enforce the various labelling and consumer guarantee laws that abound to stop “fake wasabi” products being called Wasabi, then wasabi will always remain a niche product for the connoisseurs.
While the previous main reason for consuming Wasabia japonica was the unique taste, it is interesting to note that the active components, the Isothiocyanates appear to have some positive anti-cancer and health benefits in the body. This will lead to increased production and consumption of this interesting perennial crop, but as a Nutraceutical (health food) – not as a food flavour. This will require a lot more growers who are prepared to use the Sawa growing method. More information can be obtained here on becoming a Sawa Wasabi Grower.
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Naturally Occuring Glucosinolates (116 different R groups)
Table 1. Glucosinolate structure, Radical Name, Trivial Name
The structure formulas and radical names are links to the datasheet of the individual glucosinolate. Each datasheet contains: structural formula, name of the radical, molecular formula of the radical, molecular mass of the radical the name according to Chemical Abstracts, the CAS Registry Number, trivial name, molecular formula, molecular mass, the plant species in which it has been identified and the literature reference.
|No||R||Radical name||Trivial Name|
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