The substance that makes them hot is called capsaicin, and it's mainly present in the pepper's inner veins (the tissue that holds the seeds together). As long as the pepper's crust doesn't break, it will stay inside. Maybe this chemical food stuff might interest @GopherTI make Thai soup with the same pepper phenomenon. As long as you don't slice them open, most of the heat stays inside the peppers. Even as a leftover after days in the fridge. Kind of surprising the heat doesn't diffuse more.



