Molecular chemistry debunks a flawed pasta cooking technique

If you boil your oil pasta, stop. At present. Seriously.

Perhaps you’ve come across a cookbook or site that advises you to pour olive or canola oil into the pot of boiling water that cooks your rigatoni. Maybe you have a family member who swears by this method, claiming it keeps water from overflowing and pasta from sticking together.

Adding olive oil to a pot of simmering tomatoes can do your sauce a lot of good, but adding oil to boiling water can seriously mess up your spaghetti. If you don’t trust me, trust the chef and restaurant owner Lidia Bastianich, who would have said, “Do not add – I repeat, do not add oil to your pasta cooking water!” And that’s an order! And if you don’t trust any of us, here’s the science.

Adding olive oil to a pot of simmering tomatoes can do your sauce a lot of good, but adding oil to boiling water can seriously mess up your spaghetti.Shutterstock

Does adding oil to pasta water work?

The idea behind oil preventing water from boiling on the pan comes from the fact that since oil and water don’t mix, the oil will coat the top and prevent any spillage. Let’s unbox this.

First of all, why does the water sometimes overflow when cooking pasta? Well, part of the answer is simply that by adding pasta to the pot, you leave less room for water. The other part has to do with surface tension.

Water molecules have a positively charged end and a negatively charged end. Opposites attract, and so the composition of water creates an invisible network of molecules aligned end to end. This net makes it more difficult for objects to penetrate through the surface, which is why some materials can float without falling. When it comes to boiling, the water itself does not foam when heated because the surface tension created by the invisible net prevents the bubbles from breaking through.

It’s only when pasta, which contains protein, gluten and other organic substances, mixes with water molecules. Some components of pastes dissolve while others do not. The parts which dissolve, called polar, gather on the surface and mesh with the molecules; the parts not soluble in water, qualified as hydrocarbons, stick directly. These components disrupt the tight, invisible net created by water molecules, leaving more room for the surface to expand into bubbles – and, of course, overflow.

But when you add oil, things change. Oil does not mix with water. It visibly disperses into smaller droplets throughout the liquid. Droplets on the surface interfere with bubble formation. When a bubble of foam begins to form, it comes into contact with a droplet of oil. The simple difference in surface tension of water versus oil causes the bubble to burst, preventing the water from foaming on the surface.

The idea behind oil preventing water from boiling on the pan comes from the fact that since oil and water don’t mix, the oil will coat the top and prevent any spillage. Shutterstock

So why shouldn’t I do it?

Even though the oil interrupts the surface tension of the water, it can prevent the sauce from sticking properly and coating the pasta. Although the oil covers the surface of the water, this means that when the pasta is drained, it breaks through the top oily layer.

Rest assured that the same effect does not come with oil-based sauces. Add olive oil to the tomato sauce as much as you want.

And if you want to prevent the pan from overflowing, you have several options. You can watch and stir the pot whenever it seems about to boil over, you can cook the pasta without a lid, or you can open the lid with a wooden spoon to release the steam that builds up.

How to cook pasta better?

Give the boiling water a good salt. While it’s true that salt can lower the boiling point of water, theoretically causing your pasta water to boil sooner, the amount of salt that would do the trick would also likely be too much for your palate. But, a generous pinch of salt will flavor the water and your pasta.

Save the pasta water and add it to sauces as needed. Starchy water will help sauces coat the pasta better and will also thicken the sauce.

Do not rinse the pasta after draining it; which will also rinse away surface starches that help other substances coat and stick to it.

Drain the pasta a few minutes before it is al dente. Then, toss it in a heated skillet with your sauce of choice to finish cooking while bathed in flavor.

What if you don’t trust Lidia Bastianich? Trust genuine Barilla pasta brandwho just wants you to have the best plate of pasta possible.

PLEASE CHECK is a Reverse series that uses biology, chemistry and physics to debunk the biggest food myths and hypotheses.

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