What does vigorously boiling water do?

[LoveKnowledge]

IF I am cooking something like potatoes, vigorously boiling water won't reduce my cooking time. What does it do then?

 

[Upisoft]

IF I am cooking something like potatoes, vigorously boiling water won't reduce my cooking time. What does it do then?

Its transforming the water into steam. Faster...

 

[pallidin]

Actually, there is more to it.
Vigorous boiling opens the cells of the material, allowing a more ready infusion of both water and extra ingredients, such as spices.
As boiling water has a higher temp than non-boiling water cooking time is, in fact, reduced.

 

[Danger]

As boiling water has a higher temp than non-boiling water cooking time is, in fact, reduced.

But rigorous boiling is no hotter than a simmer. All that is does is waste input heat. Water cannot exceed 100° and remain in the pot.

 

[pallidin]

Ok, that makes sense.

 

[D H]

But rigorous boiling is no hotter than a simmer. All that is does is waste input heat.

The term is vigorous, not rigorous. A vigorous boil (aka a rolling boil or a roiling boil) does a lot more than wasting heat. You don't want to use a rolling boil for something delicate such as eggs or cauliflower heads because if you do the eggs will break from all the bouncing that goes on while the cauliflower heads will be torn to shreds. You do want to use a rolling boil for something like spaghetti because if you don't you will end up with an inedible lump of pasta.

Water in a gentle boil is at 100 C, as is the water in a rolling boil. The difference between the two lies in the amount of motion and commotion going on.

 

[gmax137]

The difference between the two lies in the amount of motion and commotion going on.

I always figured that the increased 'motion & commotion' also increases the heat transfer coefficient between the liquid and the 'food' such that the food is being heated faster.

Also, if the water is just barely simmering, it is probably hotter down at the bottom of the pot (the water near the top may not be boiling). In a true rolling boil, the water is well mixed and boiling throughout.

 

[Danger]

The term is vigorous, not rigorous.

That was a typo on my part. Right finger; wrong movement. I went up to the left instead of down to the right, which tends to happen when one has no spatial sense.
I have had no success with either pasta or rice, which your post might explain. If I can find a clean pot somewhere (I've already used the 11 that I'm aware of), I might give it a try. Still, though, a vigorous boil tends to just force water out of the pot and mess up the burner. A "rolling boil", on the other hand, is just slightly above a simmer and doesn't cause an unnecessary mess.

edit: I wasn't ignoring you, Gmax; you posted that while I was composing mine, so I didn't notice it.

 

[D H]

A "rolling boil", on the other hand, is just slightly above a simmer and doesn't cause an unnecessary mess.

This might explain your problem with cooking spaghetti. You do not want the water just slightly above a simmer. That water needs to be moving so as to avoid having clumps of glued-together spaghetti noodles at the end. The resultant splatter is to some extent an inevitable byproduct of the process. You can cut down on the splatter by using a tall pot and not filling the pot full of water. Leaving quite a few inches between the top of the pot and the top of the water will keep most of the splatter in the pot.

 

[Danger]

You can cut down on the splatter by using a tall pot and not filling the pot full of water. Leaving quite a few inches between the top of the pot and the top of the water will keep most of the splatter in the pot.

Aha! If I ever again buy spaghetti noodles, I'll try that. I've always used a pot that was just large enough to hold what I was cooking, so as to avoid wasting energy heating up excess water. That still begs the question of where I might find a new pot. If it means that I'll have to start washing the old ones, I'll be very ticked off.

 

[D H]

If it means that I'll have to start washing the old ones, I'll be very ticked off.

There are some disadvantages to cooking with technicolor unwashed pots. Food cooked in those biology-experiment-run-wild pots can have deleterious affects.

For example, some people end up looking like this after eating such a meal:[PLAIN]https://www.physicsforums.com/customavatars/avatar24024_1.gif.

Some solutions:
1. After cooking, swirl the pot with water, wipe off most of the scum, and call it "camp clean".
1. After cooking, put the pot on the ground. Call Rover.
2. After cooking, put the pot outside next to a fire ant mound. Don't call Rover.

 

[D H]

Regarding your problem with rice, just follow the directions. Some Americans and Canadians think rice is supposed to be fluffy. Where they got that idea, who knows? Rice is supposed to be sticky (but not wet). Sticky rice has many qualities that fluffy American rice lacks. You can eat it with chopsticks. You can wrap it with raw fish and eat it with your fingers. You can even use it to glue bricks together: http://news.xinhuanet.com/english/2005-02/27/content_2626135.htm

"Thus we can conclude that the sticky material [glutinous rice porridge] was in the mortar," Qin said. The use of this sticky material, Qin said, helps explain why many ancient Chinese brick structures are still standing.​

 

[gmax137]

A "rolling boil", on the other hand, is just slightly above a simmer and doesn't cause an unnecessary mess.

My scoutmaster told me a rolling boil is when it keeps boiling even if you stir it with a big spoon. I think rolling boil is way above a simmer.

This might explain your problem with cooking spaghetti. You do not want the water just slightly above a simmer. That water needs to be moving so as to avoid having clumps of glued-together spaghetti noodles at the end.

My Italian aunts-in-law say to add the pasta to the rolling boil (this way the boiling doesn't stop while the pasta is going in). But then they said to turn it down a bit. You can see the pasta circulating so it doesn't stick together, but not boiling so hard that it breaks up (more likely with 'edgy' shapes like rotini).

Aha! If I ever again buy spaghetti noodles, I'll try that. I've always used a pot that was just large enough to hold what I was cooking, so as to avoid wasting energy heating up excess water.

using a big pot with the same amount of water shouldn't waste any energy. and since you don't clean your pots, the extra amount of pot to clean won't bother you.

 

[Danger]

Some of you people are starting to make sense. That scares me.

 

[Barwick]

I always just put olive oil in the water when I cook spaghetti... no lumps :)

But to answer the question: a vigorous boil should in theory cook faster than a slow boil because, as long as the object being cooked is at less than 100C, it is constantly absorbing energy from the water around it. This creates a localized area of say 99C (or maybe 91C, or whatever) around the object that somewhat insulates the object being cooked.

I guess, kinda think of it like Wind Chill... It's really only -5C outside, but when the wind's blowing, it *feels* like -15C.

 

[MagnetDave]

The motion of a rolling boil has a lot of effect on the food. The beating of the chunks of food against each other can radically change the final product, both in texture and in taste. For instant, roasted potatoes I want to rough up, to produce a starchy paste on the outside. Spaghetti is different - i want to keep its integrity. The rolling boil also transmits heat better, as Barwick explains just above.

The functional difference is the temperature of the pot - a hotter pot will produce a more vigorous boil, because it is NOT in equilibrium with the water. The hotter the pot, the more vigorous the boil, until the Leidenfrost effect kicks in.

 

[pallidin]

Some of you people are starting to make sense. That scares me.

That's OK Danger.
I am now confident that should you ever invite me over for dinner, spaghetti is now a menu option.
Uh... i'll bring the cooking pot.

 

[Danger]

Uh... i'll bring the cooking pot.

That's cool; I still have Lucy's supper dish. I'll have to nuke the food, though, because it's made out of plastic. (I hope that you don't mind the taste of left-over Purina.)

 

[pallidin]