Most of the flour you’ll find in grocery stores is made from “soft wheat,” which accounts for about 80 percent of the world’s total wheat crop, according to a major flour brand. Bob’s red mill. While soft wheat is perfect for many baked goods, pasta makers need something with more protein. The protein content of flour is very important because protein equals gluten, and gluten is what gives dough structure. Dough should contain a variety of unique shapes without turning to goo when it boils, so you need high gluten flour. Durum wheat is an extremely tough form of wheat (durum means “hard” in Latin) that requires enormous force to grind, but contains an extremely high level of protein, which makes it perfect for pasta, for example. Food52.
But choosing durum wheat is not specific enough, because America’s Test Kitchen explains that there are two general types of durum flour: durum flour, which is finely ground like all-purpose flour, and durum semolina, which is more coarsely ground, like fine grains of sand. The Test Kitchen warns that regular durum wheat flour can result in a gummy dough, so it’s best to choose durum wheat semolina. Bob’s Red Mill explains that durum wheat semolina contains 13% or more protein, compared to only 8-11% protein in all-purpose flour, concrete proof of the superior strength of durum wheat. This strength translates into the delicious chewiness we love from pasta, so while semolina may be a bit more expensive, it’s worth it.