Why does cooking oil stop water from boiling over?

[goldengrain]

Originally Posted by NCyank

How To Avoid Boil Over When Cooking Pasta

Personally, I don't like oil in my pasta. I just add the pasta to boiling water and then turn the heat down.

Me, too.
I have heard it said that the oil coats the pasta which prevents the sauce from clinging to it later.
My real reason is that there is just a lot of fat in my diet and I want to eliminate it where I can.

I have heard Rachel Ray say she put a bit of olive oil in the pot because that's going to be in the sauce, anyway.

The thing is, if you google it, olive oil seems more time than not to not actually contain actual olive oil, or even any oil that is good for you. I read an article that said 'they' are so tricky these days, that you can not detect the difference.

My husband says if you rest a wooden spoon across the top of the pot the water will not boil over. It breaks the surface tension of the bubbles. I don't know how reliable that is.

[goldengrain]

Originally Posted by GillyGx

To answer the actual question, rather than go on about whether or not you should put oil in your pasta, which you didn't ask.

The boiling point of water is 100 oC. The boiling point of oil is much much higher. In the case of certain oils as high as 270 oC and then it isn't exactly a boiling point as in boiling over, it's called a smoking point - the point where the oil starts to break down.

So, if you add oil to water, the boiling point of the contents of that pan have now been altered (increased) and the water will no longer boil over at 100 oC.

Thank you very much for this explanation. I have an electric range and some burners are hotter than others. When I switched from using oil to just salt in the water, it did seem as though the boil was more vigorous. I like to keep it at a rolling boil for the entire process. I just use a very big pot.

I thought it was just my imagination.

[maggie2101]

Why does laying a wooden spoon over the top of a boiling pot of pasta keep it from boiling over? I've never been able to figure out how that works, but it does.

[mrs.cool]

How do you keep the spoon from sinking?

[goldengrain]

It does not sink because you lay a big wooden spoon from one end of the lip of the pot to the other.

I think it must have something to do with interfering with the surface tension of the bubbles? Maybe the bubbles get that high and the spoon does this, or the steam gets somehow redirected?