Recipes often instruct you to remove the seeds from a spicy pepper if you want less heat, which seems to imply that the seeds are the source of the fire. But while removing the seeds might help a little, they're not the true producer of heat!
Kitchen Fact: A chile pepper's spicy heat comes from the pith and ribs of the pepper, not the seeds.
Capsaicin, which is the chemical compound that contains fiery heat, is actually concentrated in the inner white pith or rib of the chile pepper. While the seeds may be coated with some of the capsaicin since they're in contact with the rib, they themselves don't actually contain any heat.
This is a good reminder that if you want to take some of the heat out of the pepper, be sure to cut away and remove the pith and rib in addition to the seeds!
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(Image credits: Henry Chen)