Al dente means "to the tooth" or "to the bite" in Italian. It refers to the need to apply sufficient pressure while masticating so that firmness can be felt.
While the expression is most commonly used to describe pasta that has been served at this degree of firmness – generally considered to be the the most widely preferred – it can be used to describe any food for which the al dente sensation is particular, such as rice and tender-crisp vegetables.
The expression al dente should be considered laudatory, and in no way refers to foods being underdone or too hard.
Serving pasta al dente
Pasta is most widely known as a shaped, dehydrated, raw, enriched wheat durum semolina dough and the following deals in the preparation of such. As the pasta enters boiling water, it hydrates and wheat proteins and starches form coherent structures under the influence of heat. The process occurring from the outside-in, the pasta is allowed to retain its shape and the al dente sensation is most often and wrongly procured, in dehydrated pasta, by a slightly less hydrated peripheral core.
The amount of water to bring to a boil greatly varies. While it's possible to cook 500 g of pasta in about 4 L of water, the water will become viscous from the starch that is lost from dissolution and mechanical action of the steam pockets rising from the heat source. The residual starch, at the origin of the viscosity, affects the final dish in its composition, as it contributes to the adhesion of other ingredients – such as spices – to the pasta. This layer of residual starch also absorbs liquids in a superficial manner while partially dissolving into sauces, thereby perceptually blending the taste of the pasta and that of the added liquid ingredients.
Certain dishes, such as pasta pomodoro, will benefit from more residual starch while others, like pasta salads, will benefit from less.
The addition of salt to the pasta's boiling has two effects: the first is that is increases the boiling temperature, and the second is that the salt will permeate the pasta, imparting it its taste. The use of salt in the boiling water greatly affects overall dish composition; while certain prefer to use a salted sauce over unsalted pasta, others prefer to not salt their sauces – where the addition of sodium would affect consistency, for instance – and to salt the pasta's boiling water. In domestic and in some professional settings, it is also not uncommon for both, the water and the dressing, to be salted.
The boiling temperature, in turn, affects overall pasta density. A lower boiling temperature means more dough is hydrated before it has cooked and is able to exert pressure on the hydrating and cooking core. It is then possible to imagine that al dente pasta should be partially cooked in water containing a fair amount of salt and then finished in a more solute bath, this, to achieve a high density and avoid a sticky, undercooked core that people sometimes mistake for al dente.
Cooking instructions for dry pasta sometimes call for the addition of oil to the water, most often under the pretext that is prevents pasta from sticking together. The statement is obviously fallacious, as oil's density is lesser than that of water and therefore floats. The addition of oil to the boiling pot may, however, control "boil-overs", this, in being mechanically emulsified by the surfacing bubbles and then affecting the surface tension of air pockets formed under the starchy water's surface, preventing their accumulation.
To prevent boil-overs, it is generally considered more efficient – energetically and in labor – to control temperature than to add oil or surfactants to the water.
Addition of Pasta
Once the water bath has reached its maximum temperature – when it boils – pasta should be added and stirred so as to prevent the individual hydrating dough parts from superficially merging. Once the water returns to boiling temperature, heat should be lowered to maintain the bath at simmering temperature, so as to benefit from the mechanical action of the rising steam pockets while avoiding boil-overs.
Drainage should occur slightly before the pasta is considered al dente, this, to allow for continued hydration and cooking during the process, during further processing – such as after adding the pasta to a sauce – and during transition.
In certain dishes – such as cold pasta salads – the pasta does not often benefit from a starch coating and a lighter, fluffier texture is preferred. It then becomes efficient to rinse pasta, to free it of its residual starch and cool it. It is also possible to rinse with hot water to, likewise, control the amount of residual starch and the temperature of the pasta.
Al dente pasta is pasta that is served in this manner and which remains so throughout the meal. It should be firm, without being sticky so as to provide a pleasant experience nor should it be underhydrated, so as to favor proper digestion.
Quality control should occur at the plating level, when the pasta is ready to be served. If the pasta has the proper density and if the dish is served at the right temperature, the pasta should remain edible throughout the entire course.