Meat often gets tough from boiling while if it's simmered it gets tender. I'm sure someone has a scientific reason. Also, sauces that need a long cook time may burn if they boil all along, but not if they simmer.

When boiling, proteins denature and contract, meat gets tough, stocks get cloudy, and connective tissue turns to rubber bands instead of adding to the mouthfeel of the sauce.

Cooking gently just below boiling is generally better.

Dairy products (milk, cream and the like) may also require simmering rather than a boil.

Boiling can also change the flavors in foods with natural oils. Anson Mills recommends that their grits and polenta be cooked in a slow cooker to preserve the taste which is carried, in part, by the natural oils in the corn.

If you're making a sauce which relies on eggs for emulsification, boiling will raise the temperature past the point at which the eggs can hold other ingredients in an emulsion. You end up with scrambled eggs instead of the bearnaise or custard you were trying to make.

Cheryl

If you can't get a true simmer on the lowest setting, you may wish to invest in a 'flame tamer'--there are lots of types, but the one at the link is typical.

It just raises the pot a little higher off the flame and makes the flame a little less efficient at heating the pot.

Here is a link that might be useful: flame tamer

Simmer is important, although I don't have a special burner, I have to turn mine down as low as possible. I simmer eggs when I boil them so they don't get knocked around and broken during cooking, I simmer stock for a long time for flavor and I simmer braises and soups like chili on the stove top, to develop flavor and tenderize the meat while thickening the stock and avoiding scorching.

Puddings and sauces often need a simmer to avoid eggs or diary overcooking and curdling and if you boil cornstarch you'll lose the thickening action that you're looking for.

You definitely need to simmer, not everything can be cooked at full heat or roiling boil.

Annie

My cooktop came with a simmer plate (heat diffuser), to put on top of the grid to distribute the heat for a true simmer. I've used it, but rarely, because my burner simmers pretty well without it

You can buy one.

RyseRyse, You might check your manual or with the manufacturer. There might be a way to adjust the burner.

~Ann

Excellent answers, everyone!

I sort of knew much of this but you have made it all clear and concise.

Jim

I also use a heat diffuser, purchased at Williams Sonoma, really helps keep things at a simmer. Sometimes I think good quality cookware and good quality appliances are almost too good.

Ryse, mine won't either. I should probably clean the burner holes; I'm sure the gas not coming out evenly has something to do with the flame putting itself out when the gas is turned low. Do you have a slow cooker? I find them to be more useful now than when I had an electric stove. Sometimes I pour boiling water in mine to speed up the process.

I have one of the diffusers that I used a lot on my old stove. Used it primarily when I was done but wanted to keep things warm, turn off the burner, put the diffuser under it and all was well. For a gas stove an easier trick than that is to just take a grate from another burner, put it on top of the one you're cooking on. It'll lift it higher, be nice and stable and accomplish the same thing without extra expense or another gadget to store. If it's too much so it's not warm enough, simply turn up the heat a bit.

I was going to buy a flame tamer not too long ago.....but procrastinated, as usual.
And several days later I was cleaning a kitchen cabinet and found one that was my mother's.....it is really old but works well.
(My mom died in 1969, just to give you an idea of how old it is.)

As long as water is boiling, it makes no difference to the food if it's boiling quickly or slowly, it is going to be 212 F.

Therefore if your intention is to simmer, make sure it is not boiling slowly. With the cover on the pot, it actually does not take much fire to be boiling and not simmering.

dcarch

dcarch,

It took a minute or two for me to get your point but I think I understand it now. I think you are saying that boiling slowly is not the same as simmering. A simmer must not boil at all. Right?

Now I am wondering how much variation in temperature can be achieved at a simmer.

Jim

Jim, boiling is 212F, no higher, no lower. Simmer boiling has the advantage of your not having to add water to the pot all the time. To the food, it is 212F.

I simmer more than most people. That is what sous vide should have been called, "controlled simmering".

Sous vide simmers at exact temperatures (+ - one degree F) below boiling point.

I have a pork shouder being simmered now, at 152F for 24 hours.

dcarch

Thanks dcarch. The picture gets clearer. I'm getting a deeper understanding of the importance of controlling cooking temperature, whether by sous vide or more primitive methods.

Jim

Thanks, Cynic! I'll give that a try.