why put salt in boiling water for pasta
There are few ingredients in your kitchen pantry that serve the myriad functions that salt fulfills. In most cases, we use salt в some conservatively, others more liberally в to enhance the flavors of our food. Why that is, exactly в well thatвs a question for another day. Perhaps one of the more confounding questions revolves around the use of salt in the kitchen for two specific, yet seemingly opposing tasks. When we make pasta or boil potatoes, we always know to first salt our water. Why does water boil? All liquids, including water, have an innate tendency to evaporate when left exposed to the open air, and while the rate of evaporation varies from liquid to liquid, the process of evaporation remains the same. Liquids, like solids and even gases, contain molecules that move at variable speeds through the substance depending on its state; molecules in a solid, such as ice, move much slower than those in a gas, such as steam. When it comes to boiling water, these molecules collide and transfer energy to one another, sometimes transferring enough to cause water particles to escape from the surface в this is evaporation. As more heat is added to the water, the more intense and faster these collisions become and the more particles will escape as a result. Once the water has reached a certain temperature в in this case
212F degrees в there is so much energy held in the liquid that the tendency for particles to evaporate is greater than the tendency to stay in liquid form. At this point, known as the boiling point, the vapor pressure of the water is equal to atmospheric pressure (pressure of the air around us). So why should you add salt to boiling water?
The strange but scientifically proven phenomenon that occurs when adding salt to water is known as boiling point elevation. By elevation, I mean that the boiling point is higher than it would be in the absence of salt. This in no way means that your water will boil faster, however, which is a common misconception among cooks. On the contrary, this simply means that salted water will become hotter, and your potatoes or pasta will ultimately cook faster will make your food taste better. You could, in theory, make water boil faster by adding more salt, but it d probably make for inedible noodles or spuds: you d need 3 tablespoons of salt in 1 quart of water to increase the boiling point by 1F degree. Remember, no one likes al dente pasta that tastes like a salt lick. Pasta dishes can be so wonderfulвincredibly light, unbelievably flavorfulвbut they can also be dense, stuck-together disappointments. You can help your pasta dish be its bestвwhether it s a baked lasagne, a pasta salad, or a slap-dash plate of spaghetti and pestoвby knowing a few of the hows and whys of cooking the pasta itself. When you drop pasta into a pot of boiling water, the starch granules on the surface of the pasta instantly swell up to their maximum volume and then pop. The starch rushes out and, for a brief time, the pasta s surface is sticky with this exuded starch. Eventually, most of this surface starch dissolves in the water and washes away, and the pasta surface becomes a soft solid. Many pasta recipes begin like this: Bring a large pot of water, 4 to 5 quarts, to a rapid boil. Do you really need this much water?
Well, if you re only boiling a small amount of pasta (less than half a pound), you don t need so much, but a generous pot of rapidly boiling water is helpful for several reasons: it comes back to a boil faster when you add the pasta; it makes it easier to submerge long, rigid pastas like spaghetti; and it helps to reduce sticking slightly by quickly washing away the exuding starch from the pasta surface. To keep pasta from sticking, stir during the first minute or two of cooking. This is the crucial time when the pasta surface is coated with sticky, glue-like starch. If you don t stir, pieces of pasta that are touching one another literally cook together. Add salt, but not oil You may have heard that you can avoid sticky pasta by adding oil to the pasta water. This can prevent sticking, but at a great price. Pasta that s cooked in oily water will become oily itself and, as a result, the sauce slides off, doesn t get absorbed, and you have flavorless pasta. Adding oil may keep the pasta water from bubbling up and boiling over the rim, but this can also be achieved by making sure you use a large pot and also by reducing the heat a little (but still maintaining a boil). This is a much better solution than greasing your pasta and sacrificing flavor. Salted water flavors the pasta. A generous amount of salt in the water seasons the pasta internally as it absorbs liquid and swells. The pasta dish may even require less salt overall. For a more complex, interesting flavor, I add 1 to 2 tablespoons sea salt to a large pot of rapidly boiling water. By the way, the claim that salted water cooks food faster (because of its higher boiling temperature) is exaggerated; you re not adding enough salt to raise the temperature more than about 1ВF. Behind every great pasta is a great sauce.
And it s not just the flavor of the sauce that matters, but when and how the sauce and the pasta get combined. Toss hot pasta with hot sauce quicklyвwithout rinsing itвso the pasta absorbs more sauce and flavor. As it cools, the swollen starch in the pasta crystallizes and becomes insoluble, and the pasta won t absorb as much sauce. Just so there s no delay, I always prepare the sauce first in a large skillet, even if it s simply olive oil, garlic, and pepper flakes. The second the pasta is done (I like it just a breath beyond al dente), I scoop it out of the water with a big Chinese ladle-type strainer or spider. I let the pasta drain over the pot for a few seconds, and then I dump it into the hot sauce, stir well, and set a lid on the skillet. I let the pasta sit, covered, to absorb the sauce for a minute or two, and then I remove the lid, stir again, and serve instantly. Rinsing the pasta after cooking is a bad idea for a couple of reasons. It can cool the pasta and prevent absorption of a sauce, and it can wash away any remaining surface starch, which at this point in the cooking can work to your advantage. The small amount of starch left on the pasta by the cooking water can thicken your sauce slightly. For pasta sauces that include egg, like carbonara, it s a good idea to reserve a bit of the pasta cooking water to stir into the sauce. In this case, the starch-enriched water not only thickens the sauce a bit, but it also helps prevent the egg from curdling when it meets the hot pasta.
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