Most home cooks know that the trick for tempering the heat of a chili pepper is to remove the seeds. The reason why it often works: Conventional wisdom holds that a pepper’s power is concentrated in the placenta—the central core of the fruit that contains the seeds, otherwise known as the pith—and the thick veins that attach the placenta to the pepper wall. Removing the seeds, then, usually results in removing the placenta and veins, thus cooling the fruit’s heat.
Another trick: Sometimes it’s possible to determine the heat of a pepper just by looking. Because capsaicin, the substance that makes chilis hot, is a yellowish liquid in its pure form, yellow veins often indicate more spice.
“If you go to the grocery store, and, say, pick six jalapenos up, and cut them open and look at those veins, the more yellow you see, the hotter the jalapeno,” said Paul Bosland, a professor of horticulture and director of the Chile Pepper Institute at New Mexico State University.
Even when all those pieces are removed, though, some peppers—de-veined, de-seeded, and not yellow—still have a heat that just won’t chill, befuddling casual cooks and researchers alike.
For example, the ghost pepper, which doesn’t have many veins or appear particularly yellow, shouldn’t pack such a punch. But in 2007, Guinness World Records certified the ghost pepper as the world’s hottest chile pepper—some 400 times hotter than Tabasco sauce. (Pepper heat is measured in Scovilles, a unit based on the number of heat-producing alkaloids a pepper contains.)