What Makes Jalapenos Hot?

Capsaicin, the chemical that gives chiles their heat, is concentrated around the seeds and in the ribs. The flesh of the chile that is closer to the seeds will be hotter than the flesh near the tip.

Do the seeds in a jalapeno make it hot?

Kitchen Fact: A chile pepper's spicy heat comes from the pith and ribs of the pepper, not the seeds. ... 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.

Why are some jalapenos hot and others are not?

Chili Pepper Madness notes that there are a range of factors that make some jalapenos hotter than others, include the age of the fruit; how thick the inner placenta that holds the seeds and pith might be; and the climate, soil, and moisture of the location where it was grown.