Unlike the zing of chilli peppers, the spiciness of wasabi is felt not just in the mouth, but also in the nose. This characteristic is shared with horseradish, which along with mustard is a member of the cruciferous plants belonging to the Brassicaceae family. However, wasabi grows like cabbage and the part of the plant used for human consumption is a vertical, leafy rootstock, from which the leaves are removed, making it appear like harvested Brussels sprouts.

Originally local to Japan, wasabi is now also grown in Korea, the USA (on the west coast of Oregon and the east of North Carolina) as well as New Zealand. Wasabi thrives best in clean, shallow bodies of flowing water (such as mountain streams) and in a climate that is not too warm and not to cool (8 to 20° C). Furthermore, wasabi does not like direct sunlight, which is why most of the time artificial shade is required. All of this limits possible areas for growing; this is one of the reasons why real wasabi is rare and expensive.

Like mustard and horseradish, wasabi owes its pungent spiciness to short-lived mustard oils called isothiocyanates; these in particular being glucocochlearin and sinigrin here. And this is what makes fresh wasabi so unique.

Wasabi isn’t just called “green horseradish”, the lion’s share of wasabi pastes and powders sold outside Japan actually consists of the considerably cheaper white horseradish, dyed green with artificial colouring agents (e.g. E 102 and E 133) and flavoured with mustard or mustard extract. A look at the list of ingredients will normally confirm this.

If powder is being used, it should be mixed with the same amount of water for 10 to 15 minutes before use to create a viscous paste.