The right way to cook pasta.
ANYONE WHO PUTS SPAGHETTI IN HOT WATER for ten minutes or so and expects a good result is bound to be disappointed. Simple though it is, the cooking of pasta raises a number of questions. The first has to do with salt: Must it be added to the cooking water and, if so, why? Is it really necessary to add oil to the cooking water? How can pasta be prevented from sticking?
At home one can quickly make good pasta from scratch by mixing flour (usually made from wheat, but corn or chestnut flour may also be used), a bit of salt, water, oil, and eggs. Long kneading gives body to the pasta, which is then rolled and cut up before being cooked for three to six minutes. During cooking the starch granules absorb water and expand, and the proteins in the egg and flour form an insoluble network that binds the starch granules tightly together, limiting the extent to which they are washed into the cooking water.
Cooks can prevent homemade pasta from sticking by increasing the proportion of egg. If the protein network is formed before the starch swells up, the pasta remains firm during cooking and doesn’t stick; if the starch swells up before the protein network forms and the pasta is cooked, part of the starch (chiefly one of two types of molecule called amylose) has time to diffuse in the cooking water, so that the surface of the pasta is coated with the other type of molecule (amylopectin) and its strands stick together. After straining, a chunk of butter or a bit of olive oil will keep the hot pasta from sticking on the plate.
To improve commercial manufacturing techniques, Pierre Feillet, Joël Abecassis, Jean-Claude Autran, and their colleagues at the Institut National de la Recherche Agronomique (INRA) Laboratoire de Technologie des Céréales in Montpellier sought to determine which proteins give pasta its distinctive culinary qualities.
Hard-Grain Wheat Gluten
Commercial producers make pasta from hard-grain wheat. In the absence of egg the protein network is formed by proteins in the wheat and, more precisely, in its gluten. If one takes the mass obtained after kneading flour and water for a long time and then rinses it under a stream of running water, the elastic matter that remains is composed of gluten proteins. Because this substance is more abundant in hard wheats than soft ones, laboratories such as the one in Montpellier are interested in the composition and genetic variability of hard-wheat proteins and in methods of making of pasta that favor the formation of a protein network.
The quality of a good commercial pasta is judged by its yellow-amber color and its culinary properties, which is to say the likelihood that it will not stick after cooking (or even after being slightly overcooked). Plant geneticists therefore have looked to develop hard wheats with firm and elastic gluten. The INRA biochemists showed that this latter characteristic is associated with the presence of a particular protein, gamma-45 gliadin, common to varieties of hard wheat that are rich in glutenins of low molecular mass.
The Montpellier team also investigated the optimal conditions for making pasta and showed that drying it at a high temperature (about 90°C [194°F]) assists the formation of a network of proteins that is more rapidly insolubilized during cooking. This heat must be applied at the end of the drying process in order not to damage the starch granules. Kneading the dough and pulling it through an extrusion press with the aid of an Archimedean screw must also be done in such a way that these granules are preserved. The application of high temperatures acts on the color because it inactivates both lipoxygenases (enzymes that destroy yellow pigments) and peroxidases (enzymes that darken organic material).
Oil, Water, and Acidity
How, then, should pasta be cooked? The first thing to keep in mind is that the proportion of proteins must be high. If hard wheat is not used then one must add eggs to develop the gluten network or else patiently work the dough and carefully roll it out, using enough water to hydrate the proteins so that they are able to bind together. Whatever its composition, pasta must be put into boiling water so that cooking time is reduced and loss of starch content minimized.
Is there any reason to add oil to the cooking water? Batches of spaghetti that have been overcooked, either with or without the addition of oil, show no differences with regard to stickiness as long as the pasta does not pass through the surface layer of oil at the end. Oil is useful mainly because it coats the pasta when it is removed from the water, after cooking. Adding a knob of butter or a squirt of olive oil to the dish at the table produces the same result.
Finally, the cooking water has its own role to play. Jacques Lefebvre at the INRA station in Nantes has shown that the more proteins the water contains, the less amylose the starch loses during cooking. Therefore pasta should be cooked in a rich broth. Moreover, the Montpellier team demonstrated that cooking pasta in mineral water increases the loss of starch content and therefore stickiness as well, whereas pasta cooked in slightly acidified water (through the addition of a tablespoon of vinegar or lemon juice, for example) preserves a satisfactory surface state, even after overcooking. Proteins in water with a pH of 6 have an electrically neutral form, allowing them to combine more easily and form a network that efficiently traps the starch.