If you add vinegar to grated daikon radish, the spiciness does not come out.

The reason why grated radish is difficult is that glucosinolate reacts with the enzyme myrosinase to generate isothiacyanate.

Adding vinegar stops the enzyme action and reduces the spiciness. In addition, even if heat is applied, the action of the enzyme stops, so the spiciness can be suppressed.

Conversely, if you grate it slowly with a fine grater, the pungency will be stronger. This is because the enzyme reacts more and isothiacyanate is generated.

These reactions also occur with wasabi.

Shark skin (a file used by attaching shark skin to wood) is used for graters because of its fine grain. This is because the wasabi enzyme reacts and makes it more spicy.