What’s the difference between a simmer and a rolling boil?

To the eye, a simmer is a gently bubbling liquid that comes from a relatively small amount of heat being used. By comparison, a rolling boil is a vigorous, bubbling boil with a sort of churning, active motion that comes from using a high amount of heat.

Other than when cooking pasta or blanching vegetables, there are few times when you need to cook something with a heavy rolling boil. Cooking with that level of heat breaks apart food instead of gently cooking it, changing the texture of the food in the liquid. The rolling motion of a heavy boil jostles and bumps the food around, knocking bits off the longer it cooks.
Typically, a liquid can be brought to a boil to begin with using a high level of heat, but once the cooking begins the heat should be reduced to allow the ingredients to simmer unless the recipe says otherwise.
Last updated on January 22, 2019