Boiling and Simmering: Convection

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Boiling is cooking food in water that is boiling at 100oC (212oF). The only way to change the boiling point is by adding salt or sugar which will increase the boiling point by a few degrees, or increasing the pressure as in a pressure cooker. In contrast, the boiling point falls when the pressure is reduced, so at a higher altitude your kettle boils quicker and the temperature of your tea will be lower.

Boiling is perhaps the most popular cooking technique, because water is readily available as a cooking medium and it is very easy to see when water is boiling. But whereas boiling sterilises your food and so is recommended by food agencies around the world, it is often not the best for your food or drink. For example, tea must be boiled according to regulations in Canada and Germany, for example, but making delicate teas is best at cooler temperatures. Then for ingredients, boiling water is too high for the protein in fish or meat, but not high enough for those vegetables - a quick blast of higher temperature for vegetables preserves their colour and vitamins better. If higher temperatures are needed, then you can use a different cooking medium (e.g. oil, or increase the pressure for pressure cooking, or add another ingredient to the water, e.g. sugar, to increase its boiling point.

Nuances on boiling include simmering and stewing:

  • Simmering is cooking just below boiling point, with the liquid on just trembling. The usual simmering temperature is 96 - 98oC (205 - 209oF), but for meats is lower as in stewing, so 82 - 87oC (180 - 189oF). But the temperatures used in simmering are imprecise and relate more to the temperature to coagulate the proteins, kill harmful microbes, or soften the tissues for easier digestion. A good of rule of thumb, though, is that cooks generally use too high a heat, so reduce the simmering temperature will generally improve their food!
  • Stewing is generally used to cook meat on a hob; stewing is not boiling and should be done in a pot with a tightly-fitting lid and at a temperature below boiling point, i.e. it is effectively the same as simmering. This enables the proteins in meat to coagulate at the necessary lower temperature than boiling point that spoils the texture of a stew - meat proteins cook at below 90oC (194oF). You should use little liquid should be used as possible to enable the gravy to become as thick as possible.

Finally, once your cooking water is boiling, it will heat no further, so it is sensible to reduce the heat to a gentle boil rather than a roiling boil. As Accum wrote:

"Count Rumford has taken much pains to impress on the minds of those who exercise the culinary art, the following simple but practical, important fact, namely; that when water begins only to be agitated by the heat of the fire, it is incapable of being made hotter, and that the violent ebullition is nothing more than an unprofitable dissipation of the water, in the form of steam...it is not the bubbling up, or violent boiling, as it is called, that culinary operations are expedited."

Further Reading

  • Davidson, A. (1999) The Oxford Companion to Food, Oxford University Press. ISBN 0192115790.
  • Stobart, T. (1981) The Cook's Encyclopedia: ingredients & processes, Harper & Row. ISBN 0060141271.