How Is Pasta Made? Durum, Dies and Why the Shape Matters

Dried pasta is made from durum, Triticum durum, a hard wheat with a high protein content whose endosperm, when milled coarsely, gives a yellow semolina rather than a white flour. The hardness matters: durum's proteins form a strong, elastic gluten network when hydrated, which holds the starch in place as the pasta cooks so that it stays firm, al dente, and does not turn to mush, while soft bread wheat makes a pasta that goes sticky. Italian law requires dried pasta to be made from durum alone, and Italy imports much of it from Canada and Australia. Fresh pasta, the tagliatelle and ravioli of the north, is a different food, made from soft wheat flour and eggs, rolled and cut, and eaten within a day or two or frozen.

A pasta factory runs a sequence that has not changed in principle since the nineteenth century:

• •Mixing: semolina and about a third its weight of water are kneaded under vacuum into a stiff dough; the vacuum removes air bubbles that would leave white specks and weak points
• •Extrusion: the dough is forced by a screw through a die, a thick plate pierced with holes of the shape wanted, and cut by a rotating knife as it emerges; a bronze die drags on the dough and gives a rough, porous surface that holds sauce, a Teflon-lined die gives a smooth, shiny one and is cheaper and faster
• •Drying: the wet pasta is dried in chambers from 30 percent moisture to 12, over 6 to 24 hours; slow, cool drying at around 50 degrees preserves flavour and texture, fast drying at 80 to 100 sets the surface and is what most mass-market pasta gets
• •Cutting and packing: long shapes are hung over rods and cut to length, short shapes fall onto belts

The several hundred shapes are not decoration; each is engineered for a sauce. Long thin strands, spaghetti and linguine, suit sauces that coat, oil, tomato, clam; ribbons, tagliatelle and pappardelle, with their wide surface, take rich meat sauces; tubes, penne and rigatoni, ridged to hold sauce on the outside and hollow to trap it inside, suit chunky sauces; shells and orecchiette cup small pieces; and spirals, fusilli, hold thick sauces in their grooves. The regional pattern follows the wheat and the wealth, with egg pasta in the north where eggs were plentiful and dried durum pasta in the south, where the climate dried it and the poor could store it. A recipe's pairing of shape and sauce, which Italians treat as a matter of correctness, is a folk record of what sticks to what.

Cooking is hydration and the gelatinisation of starch: the pasta absorbs water, the starch granules swell and soften, and the gluten holds the structure, and the moment to stop is when the centre is just firm, since the pasta goes on cooking in the sauce. The physics explains the rules. Plenty of water and a rolling boil keep the pieces apart and the temperature up; salt in the water seasons the pasta from inside, since it will not take salt afterwards; oil in the water does nothing but coat the pasta so sauce slides off; and the starchy cooking water, which Italian cooks add to the sauce, is an emulsifier that binds oil and water into a coating. Al dente pasta also has a lower glycaemic index than soft-cooked, since the intact structure slows digestion, and pasta cooled and reheated has more resistant starch still.

The Etruscans and Romans made sheets of dough and cut them, a dish Horace and Cicero mention, and the Greek word for it, laganon, is the root of lasagne. Dried pasta, which needs durum and a dry climate, appears in the Arab Mediterranean, and the geographer al-Idrisi wrote in 1154 of itriyya, strings of dried dough, being made at Trabia in Sicily and shipped by the boatload. Naples industrialised it in the eighteenth century, with the dough kneaded by foot and dried in the sea breeze, and the mechanical press of the 1870s and the artificial dryer of 1917 made it the food of every kitchen; Italian emigrants took it to America, where the tomato sauce it is now inseparable from was standardised. Marco Polo's supposed introduction from China was printed in an American trade magazine in 1929, two years after the same magazine had published the Sicilian evidence, and the noodle of China is a separate and older invention, made of soft wheat and pulled or cut, that the two civilisations reached without each other's help.

Because gluten does so much of the work in ordinary pasta, making a version without it is a real engineering problem. Gluten-free pasta is usually made from rice, maize, buckwheat or legumes such as lentils and chickpeas, none of which forms that elastic protein network. Mixed with water and extruded like durum dough, these flours would give strands that crumble or dissolve into the cooking water. The manufacturer therefore has to find another way to hold the starch together before it ever reaches your pan.

The usual answer is to cook the starch partway during manufacture. The flour is steamed or heated and pressed so that the starch gelatinises, then extruded while hot and dried; as it cools, the starch molecules partly re-form into a firmer structure that acts as a scaffold, a process called retrogradation. Some makers add egg, extra protein or gums to help. Legume pastas bring more protein and fibre than wheat pasta, but tend to foam more and soften quickly if overcooked. That is why the cooking times on gluten-free packets deserve closer attention, and why the texture never quite matches durum's bite.

A common belief is that salt goes into pasta water to make it boil hotter. The chemistry says it does, but only just. Dissolved particles raise the boiling point of water in proportion to how many there are, and a generous dose of 10 grams of salt per litre raises it by less than a fifth of a degree, far too little to change the cooking time. Salt does not make water come to the boil faster either. The burst of bubbles you see when you tip it into very hot water comes from steam and dissolved gas forming on the grains, not from any change in temperature.

The rule about large pots is also less strict than it sounds. The food writer Harold McGee tested cooking dried pasta in a fraction of the usual water, and even starting it in cold water, and found that with some stirring in the first minutes, while the surface starch is sticky, the pieces did not clump and the texture was much the same. The method saves time and energy, and it leaves a cloudier, starchier cooking liquid that thickens a sauce more effectively. The main practical limit is shape: long strands such as spaghetti need a pan wide enough for them to lie flat once they soften.

In Italy, what can be sold as dried pasta is set by law. Since a law of 1967, dried pasta made in Italy must be made from durum wheat semolina and water, rather than from softer wheat flours, a rule intended to protect quality and the traditional product. Durum wheat's protein gives pasta its firmness and helps it hold its shape when cooked.

Fresh pasta and egg pasta follow their own rules, and some regional specialities, such as Gragnano pasta from near Naples, have protected status with additional requirements about where and how they are made, such as being extruded through bronze dies for a rougher surface that holds sauce. Pasta made elsewhere is not bound by Italian law, which is why cheaper brands in other countries sometimes use blends of wheat.

Dried pasta is durum wheat semolina and water, kneaded under vacuum, extruded through a bronze or Teflon die into one of several hundred shapes and dried slowly to twelve percent moisture, with the hard wheat's gluten holding the starch so that it cooks firm; fresh pasta is soft flour and egg, rolled and cut. The shapes are matched to sauces by how they hold them, the cooking rules follow from starch and gluten, and the food is Roman, Arab and Sicilian long before it was Neapolitan, and never Chinese.