By Harold McGee
When pasta is cooked in water, the protein network and starch granules absorb water and expand, the outer protein layer is ruptured, and the dissolving starch escapes into the cooking water. Deeper within the noodle there’s less water available, so the starch granules aren’t completely disrupted: the center of the noodle therefore stays more intact than the surface. Cooking pasta al dente means stopping the cooking when the center of the noodle still remains slightly underdone and offers some resistance to chewing; at this point, the noodle surface is 80–90% water, the center 40–60% (somewhat moister than freshly baked bread). Pasta is sometimes cooked just short of this point and then finished in the sauce that will dress it.