Why do radishes taste spicy?

Crisp and refreshing, a radish can pack a little kick. If your palate is sensitive, you may perceive its similarities to mustard, horseradish, and wasabi, which are fellow members of the family Brassicaceae. That’s because all of these plants contain natural chemical compounds called glucosinolates, which become potent thanks to some cool biochemistry. When a radish is cut, bitten, or crushed, its cells are damaged, triggering an enzyme called myrosinase to break down the glucosinolates into various metabolites, including pungent compounds known as isothiocyanates. The same process occurs in the radish’s spicier cousins, and the resulting chemicals are thought to help deter herbivores and pests.

In humans and other animals the isothiocyanates stimulate sensory receptors in the mouth and nose, resulting in a peppery, pungent flavor that is often described as sharp rather than fiery. The sensation tends to affect the nasal passages and can sometimes seem stronger than the heat of some peppers. Interestingly, the burning sensation caused by chili peppers comes from capsaicin, which works differently from the isothiocyanates in radishes.

The intensity of a radish’s flavor depends on its variety and growing conditions. Cool weather and consistent moisture generally produce milder roots, while hot temperatures, drought stress, or delayed harvesting can increase the concentration of pungent compounds. Young, freshly harvested radishes are often mildly peppery, whereas older or stressed plants may develop a noticeably stronger, spicier taste.