Cooks can improve their pasta in many ways, from using the right amount of water to being liberal with their seasoning. But one of the easiest ways to make a restaurant-quality bowl of spaghetti is to skip a step altogether. According to Food & Wine, you should never rinse your pasta after cooking it—except when making a specific type of recipe.
When noodles boil, they release starch. Most people don't notice it, but it's an essential ingredient in many classic pasta dishes. Cloudy, starchy water is better at thickening and binding sauces than plain water from the tap, which is why many recipes will tell you to reserve a cup of your cooking liquid.
Starch also will help sauce cling to a strand of bucatini or a rigatoni tube. Strained pasta is covered in a layer of starchy film. When you add that cooked pasta to a pan or pot with sauce, the sauce will adhere to the starchy coating. Without that coating, the sauce will slide right off. This is why you should never rinse your pasta: Washing the starch off with water will leave you with naked, flavorless noodles sitting in a pool of sauce instead of an integrated dish.
There is one exception to the never-rinse rule, and that's pasta salad. Pasta that's meant to be eaten cold has different requirements than a hot dish. Starch congeals as it cools, resulting in an unpleasant, gummy texture. Rinsing the product as soon as it's done cooking prevents this issue, and it also gets rid of any residual heat that may overcook your noodles.
If you know what you're doing, it's easy to elevate a pasta dish into a gourmet meal. The recipe doesn't have to be complicated: This simple pasta sauce requires three ingredients, and it's been hailed as one of the world's best.
[h/t Food & Wine]