Why do you add salt/oil to boiled water for pasta?

Boiled PastaThanks to how cheap dried pasta is, this is a staple in most homes. Introduced to us by the Chinese (and later the Italians) it always makes for a delicious meal.

Cooking it should seem simple enough, boil water, add pasta. Take out when done, rinse and eat! But then someone told you about adding salt and oil to the water… and you were all “huh”? After a quick search on the Google, it looks as if you’re not alone. Not many people actually understand why we do it!

Well after reading this post, you’ll know exactly why!


Most people will claim that you add salt or sodium chloride (NaCl) for taste reasons. Salt the pot, not the pasta. Though that is correct, without food science knowledge you wouldn’t know about the other reason! Boiling point elevation.

In the case of boiling pasta, the solute (NaCl) is dissolved in another substance known as a solvent (water) which does the dissolving. I say solvent and solute, to emphasis the point that this isn’t just a “water and salt” phenomenon. It can be gas in a liquid, like oxygen in water, gas in solids, like hydrogen in metals, or solid in liquid like it is here or also in the case of sugar in water.

When a solute is added to a solvent, the physical properties of the compound change. Such as boiling point and melting point. This together this all called colligative properties. Which I won’t get much more into, mostly because this was part of one the worst courses I was forced to take in university, Physical Chemistry.

Still with me? Good. So, if the temperature at which the water boils becomes higher this means that the salty boiling water will be able to cook your pasta faster! This is because salt interrupts water’s ability to enter its vapour (steam) stage; therefore, reducing its vapour pressure. This in turn forces water to “work harder” to boil. In turn, this creates a hotter boiling water. (Click HERE for a good visual on the explanation).


So great, we know why you add salt, but what about the oil? Pasta tends to stick together during cooking when its allowed to rest close to each other just after being added to the cooking water. This is due to the partly gelated starchy surface acting like glue. This can be minimized by adding oil (1-2 tbsp) OR by simply stirring the pot for the first few minutes of cooking. Oil will also reduce the likelihood of your pot from boiling over.

Some people claim that adding oil to the pot makes it harder for sauce to stick to the pasta later. Personally, I’ve never encountered that problem. But if this is an issue for you, then just remember to stir the pasta for the first minutes of cooking and come back to check on it regularly.

bowl of cooked pasta

So there you have it, mystery solved. No longer will you have that lingering question about salty/oily water when you cook your beloved pasta dish. Your welcome 🙂


About Adi

A baker, a food scientist and an overall lover of new food creations

One response to “Why do you add salt/oil to boiled water for pasta?

  1. I reckon something really interesting about your web site so I saved to fav.

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