The heat of chilies is concentrated in the seeds and white membrane inside. By removing all or some of them, the heat is lessened.
But why not just use less amount of chilies for less heat?
Because, contrary to popular belief, flavors of chilies vary. Some are sweet, some are smoky, some are even slightly bitter. The spiciness varies too. There are times when we add chilies in our dishes not so much for added spice but to capture other flavors. There are times too when we add them for color. In these instances, we want a lot of chilies but we do not want to be overwhelmed by the heat. While some people swear that spiciness makes a dish more appetizing, there are also studies that say too much spice and the tongue loses its ability to savor other flavors.
So what do we do when we want all those reds and greens in our dishes but not the corresponding spiciness? Like I said, scrape off the seeds and the white membrane. An invaluable tip from Nigella Lawson. Slit the pepper lengthwise and scrape off the seeds and membranes with a knife or a teaspoon.
Then proceed to cut the chilies to the desired coarseness of fineness. A mezzaluna works best but a nicely curved knife will do the trick too.
Now, if there is one thing I learned from all the years of cutting and chopping chilies, it is never to touch your face, especially around the eyes, or any sensitive part of your body without washing you hands thoroughly after handling chilies. The heat of chilies is not something that can be tasted by the mouth exclusively. Don’t believe me? Try it. Don’t say I didn’t warn you. :)