If you fully drain your pasta water in the sink you’re throwing away what Italians like to call “liquid gold” that could be put to very good use. When cooking pasta, the starch releases into the water. The water should not be discarded but used to thicken your sauce because all Italians know that runny sauce is not ideal.
If you’re wondering why your sauce is so runny, this may be due to several factors. Oil and water do not mix, so the oil and water from the sauce begin to separate. This is where the pasta water comes in handy. The starch from the pasta water is known as an emulsifying agent. This means that it is able to bind together the oil and liquids which creates a sauce with the perfect consistency.
Furthermore, the starch from the pasta water creates a nice coating which allows the sauce to cling to the pasta.
If you do wish to drain your pasta, you can put several cups to the side and then add it to your sauce. Save about one cup of water per pot of pasta. Another method is to use tongs to remove the pasta from the water and place it directly into the sauce. Be sure to never rinse the pasta because it will remove the starch coating.