Archaeological evidence shows the ancient Japanese were eating wasabi as early as 14,000B.C. By the 16th century cultivation had spread, but use was restricted to the Japanese ruling class. Production increased with the rise in popularity of sushi, when wasabi became the preferred flavouring and was prized for its ability to counteract food poisoning.
Wasabia japonica is a member of the Brassica family, which includes cabbages, horseradish and mustard. Large, heart shaped leaves grow on 60cm long stems from the crown of the plant. The wasabi stem, or rhizome, is formed at the base of the plant and grows upwards above ground taking up to two years to reach maturity. It is this stem which is grated to produce wasabi paste. It is a common misconception to refer to the wasabi stem as a root or rhizome when it in fact it is neither. The term rhizome is so often used it is an acceptable name for the stem that is formed as leaves die back, much like a palm tree trunk is formed. The colour of the stem varies from a very light green to a darker green depending on variety, time of year and which part of the stem is grated. The greenest wasabi is found under the leaf stems. A purple ring formed by naturally occurring anthocyanins is often seen running through the wasabi stem. Clusters of delicate white flowers appear on long stems rising high above the plant in late winter signalling an emergence from dormancy and return to growth. All parts of the wasabi plant are edible and each carries the distinctive wasabi flavour although the strength of flavour and pungency varies considerably.
Natural defence against predators
The pungent heat produced by wasabi when eaten is a natural defence mechanism to warn off predators who would like to eat the plant. An evolutionary arms race spanning hundreds of millions of years between caterpillars and brassica plants is responsible for the characteristic heat of wasabi and other plants like horseradish and mustard. Ironically this flavour is exactly why humans consume these plants today.
Real wasabi vs. imitation wasabi
Wasabi is notoriously difficult and expensive to cultivate, as a result pastes and powders purporting to be wasabi contain very little actual wasabi. Check the ingredients and you will see horseradish, mustard powders, sweeteners, colourings and other additives make up most of the ingredients and real wasabi makes up just a few per cent. Some products masquerading as wasabi contain NO real wasabi. Try the fresh and find out what you´ve been missing. Just be aware that fresh wasabi is a beautiful pale green colour when grated and ready to eat. There’s nothing wrong with it because it isn’t lurid green, on the contrary, it’s just how nature intended it to be.
Fresh wasabi heat
The pungent heat of wasabi differs from chilli. It develops quickly and rises up the sinuses rather than holding in the mouth, then quickly dissipates. We think fresh wasabi has a very clean heat. You’ll see what we mean when you try it.
The flavour of fresh wasabi is produced when the individual cell walls inside the rhizome are broken down by grating the stems to a very fine paste. This instigates a chemical reaction between myrosinase enzymes and glucosinolates to form the all important isothiocyanates that provide wasabi’s unique pungent heat. The flavour and pungency of the fresh paste will peak after 3-5 mins and hold for 20 mins before dissipating.
It is the isothiocyanates (ITCs) produced when wasabi is grated that led to wasabi’s ancient reputation as a healthy food. Anti-microbial, anti-bacterial and anti-parasitic qualities inherent in these ITCs are very likely the source of wasabi cultivation in ancient Japanese societies. The diet often contained raw fish and wasabi was used to counter the effect of food poisoning by killing bacteria and parasites in the fish.
Along with other famously healthy members of the brassica family that produce ITCs, like broccoli and watercress, wasabi has recently become an important tool in research into cancer prevention and treatment.
Wasabi is very low in cholesterol and sodium and a source of dietary fibre and vitamin C. It is also a good source of Vitamin B6, calcium, magnesium, potassium & manganese. It is unclear how much and how often you should be eating fresh wasabi to encourage all of these benefits but research continues.