Despite a popular belief that adding oil to pasta water keeps the noodles from sticking together, Laura Schenone, author of The Lost Ravioli Recipes of Hoboken, says that adding oil does nothing to prevent pasta from clumping.
“Oil in pasta water just floats on top, and when you drain the pasta, most of it will go down the drain,” she explains. “But you’ll also get some of it on your pasta.” This coating of oil makes it harder for the pasta to absorb any sauce added later. The only instance when oil might be useful is with filled pasta; it makes the filled bits less likely to open as they collide in the boiling water. Otherwise, you’re just wasting good oil.
If you don’t want your pasta to stick together while it’s cooking, Giuliano Hazan, best-selling Italian cookbook author and cooking instructor, says to follow these steps:
1. Use a large pot and add a good amount of water so the pasta has plenty of space to move, which helps it cook evenly. Use at least six quarts of water for each pound of pasta.
2. Keep the water at a rolling boil, and cover the pot after putting the pasta in to bring the water back to a boil more quickly. Once the water is boiling again, remove the lid to prevent the water from boiling over. A rapid boil will keep the pasta moving.
3. Periodically stir the pasta while it’s cooking, especially in the first two to three minutes, because that’s when it’s at its stickiest.