That spicy kick that some like to add to their sushi is actually not what most people think it is. It's called wasabi, but in reality, it's just horseradish, hot mustard and green dye. Why is that? The actual wasabi plant is grown in only Japan and a few other select areas. It's extremely difficult to grow and very costly to import. One small piece of the plant that real wasabi is made from would cost approximately $50 and it would only yield about an ounce of the spicy condiment.
True wasabi is chemically similar to the horseradish paste served in most restaurants because they both get their flavor from a group of compounds called isothiocyanates. In the wasabi plant however, these compounds are bound to sugar molecules. The grating of the plant produces enzymes that release the sugar molecules, so in addition to the spicy kick, there's also a bit of sweet flavor. The ratios of the isothiocyanates in horseradish and wasabi differ just enough to make each produce a different taste, even though some believe they are the same substance.
