Why Do Cooks Simmer Instead of Boil?

Step 1 of 5

Water stops getting hotter at its boiling point.

Once it reaches 100 degrees, extra heat goes into turning liquid into steam instead of raising the temperature. The thermometer simply stops.

Step 2 of 5

So a fierce boil only makes more steam.

A high flame produces bubbles faster and empties the pan quicker, but every part of the food is sitting in water at exactly the same temperature.

Step 3 of 5

The violence is what damages food.

Bubbles knock delicate things apart. Fish flakes, eggs toughen, and a stew's vegetables collapse into the sauce instead of staying whole.

Step 4 of 5

A simmer holds the heat steadier too.

A gentle pan keeps its lid's worth of heat with little evaporation, so the liquid level and the seasoning stay where the cook put them.

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Which is why recipes are fussy about the words.

A simmer shows a bubble every second or two. A rolling boil is a continuous churn. They cook at the same temperature but produce different food.

A pressure cooker is the exception — it raises the boiling point itself, so the water really does get hotter.