Quote Originally Posted by Shogo View Post
On the genetic front, you could just flat out have fewer capsaicin receptors than other people. The less of these you have, the less you'll feel the burn even if you're someone who doesn't normally eat spicy foods. Conversely, people who are especially sensitive to spicy foods would have more of these receptors. (A related receptor is why mint can have a "cold" taste.)
There are hot foods that contain no capsaicin, it is perfectly possible to have a very hot sauce that contains none.

Horseradish (Armoracia rusticana, syn. Cochlearia armoracia) is a perennial plant of the family Brassicaceae (which also includes mustard, wasabi, broccoli, cabbage, and radish).

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The distinctive pungent taste of horseradish is from the compound allyl isothiocyanate.
https://en.wikipedia.org/wiki/Horseradish

Pepper gets its spicy heat mostly from piperine derived from both the outer fruit and the seed. Black pepper contains between 4.6 and 9.7% piperine by mass, and white pepper slightly more than that.
https://en.wikipedia.org/wiki/Black_pepper