Pasta Processing: Pasta production

Raw materials

There are six classes of wheat grown in the United States: Hard Red Spring, Hard Red Winter, Soft Red Winter, Durum, Hard White and Soft White. Each class has its own characteristics and recommended use. For example, Soft Red Winter Wheat is associated with low protein content, low water absorption, and is recommended for cakes and pastries⁷. Durum is the only wheat that has all the necessary qualities required to make pasta⁵.

Durum wheat produces kernels much harder than all other wheat. Durum is also the only wheat that has yellow pigments distributed throughout the entire endosperm rather than only the outer layers of the kernel¹. This means that milled durum produces yellow, granular semolina while all other wheat produce white, powdery flour. The gluten (wheat protein) found in durum is much more pliable than gluten in other wheat which leads to easier extrusion. Durum also has lower water absorption, an important factor in the pasta drying process. Pasta products made from durum hold their shape better and have a firmer texture when cooked.

It is important to remember that not all durum is created equal. Vitreousness is a key element of durum evaluation and grading. Vitreous kernels have a translucent or glass like appearance with a flinty texture. Starchy kernels are the opposite of vitreous; yellow, soft and possessing a crumbly texture. As the amount of vitreous kernels decrease, semolina extraction decreases, flour production increases and finished pasta quality decreases leading to inferior products. In the United States, durum is categorised into three subclasses: Hard Amber Durum (75 per cent or more vitreous kernels), Amber Durum (60 – 74 per cent vitreous kernels), and Durum (less than 60 per cent kernels). The best quality pasta is sourced from Hard Amber Durum.

Kernel structure and milling

A kernel of durum wheat has three components (Figure 1). The bran, or outer layers, constitutes 12 – 15 per cent of the kernel and is high in fibre and ash. The germ is the embryo of the plant. This is three to five per cent of the kernel and contains most of the lipids and other nutrients needed to uphold germination. The endosperm is 80 – 85 per cent of the kernel, and contains high amounts of starch and gluten.