The Real Reason You Should Always Use Pasta Water To Loosen Sauce

Perhaps you've watched this unfortunate kitchen scenario play out before your helpless eyes: You picked out a delectable pasta recipe to make for dinner, and you carefully followed each preparation step to a T, chopping garlic and measuring out olive oil and salting the water adequately and timing the pasta perfectly so it's al dente. You've prepared your sauce of choice, drained your pasta in a coriander and then ... you realize that you've forgotten to set aside a cup of the pasta water to add to the mix. 

Oops. You slap your forehead and desperate to stay on your pasta's schedule, you may take a bit of water from the tap and use it to loosen your sauce. Perhaps you think that water is a fine substitute for pasta water, but in fact there is a good reason why pasta water and only pasta water should be used to loosen your sauce.

The real reason that pasta water should be used to loosen sauce is because it has flavor, seasoning, and starch. It is the starch from the pasta that helps to not only thicken the sauce, but also creates a binding for the sauce to the pasta, according to Allrecipes. Using tap water will only dilute your sauce to become watery and worse, dull down the flavor of your final dish.

If you're really in a pinch and want to impress with your pasta prowess but have already thrown out the precious pasta water, luckily there are some substitutes that will do better than tap water. You can always create a slurry with cornstarch, salt, and water (you can also use flour instead of cornstarch), and Down in the Kitchen recommends combining corn flour with oil and salt or xanthan gum plus a little oil, if you happen to have it on hand. If not, when you make pasta it's best to make it a habit to always set aside a cup of the starchy liquid to better be safe than sorry and diluted.