a verb which indicates one of the fundamental cooking operations, familiar in every kitchen. Water, at sea level, boils at 100 °C (212 °F). That is not a coincidence. The centigrade scale was established by defining the freezing point of water as 0° and its boiling point, when it turns to steam, as 100°.
Nor is it a coincidence that the point at which water boils is easily recognized. When water turns to steam, the process is heralded by some bubbles coming to the surface and is accompanied, when in full swing, by rapid bubbling. So, cooks have no problem with an instruction such as ‘bring to the boil’. Even from the far side of the kitchen one can tell when this has been achieved.
This ease of recognition is a considerable convenience, and, taken in conjunction with the ready availability of water as a cooking medium, would go a long way towards explaining the popularity of boiling as a cookery technique. But there is still a fundamental question to be answered: what is it about this precise temperature which makes it suitable for cooking a wide range of comestibles? Might not 5° less or more, or even greater variations, be better?
On one level, the last question can be answered in the affirmative. It is frequently better to poach something, at a temperature just below boiling point; or to cook at a higher temperature. Since water turns to steam at 100 °C, the latter option requires using a different cooking medium (e.g. oil) or changing the water to a solution (e.g. of sugar in water, which will reach a far higher temperature) or altering the boiling point of the water by resorting to pressure cooking.
On another level, one could answer the question differently, pointing out that most foods consist mainly of water (the proportion is often more than 90%), and that it is therefore unsurprising that ‘bringing to the boil’ is an efficient way of cooking; it takes the main constituent of the foodstuff to as high a temperature as it can normally reach.
Vigorous, rapid boiling of water (or other liquid with the same characteristics) does not produce a higher temperature, but simply causes more commotion in the pot (normally pointless) and increases the rate at which water evaporates (useful if one is reducing the liquid). The point is brought out in this quotation from Accum (drawing on Count Rumford and thus uniting in one passage two of the greatest writers on the science of cookery):
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 by the bubbling up, or violent boiling, as it is called, that culinary operations are expedited.
When the cooking medium is something other than water, the situation is different; then there may well be situations in which vigorous boiling is required. See bouillabaisse for one, the point there being to create an emulsion of the water and oil. Jam recipes often call for rapid boiling at the end of the process, this being designed to promote evaporation and, by increasing the proportion of sugar in the sugar solution, to allow the jam to reach the relatively high temperature which will ensure a good set. Other examples could be given.
Finally, an interesting point from Tabitha Tickletooth in a book called The Dinner Question (1860). This extraordinary author, whose massive and matriarchal image on the cover of the book is generally supposed to represent the real male author in drag, holds forth on many topics, including potato cookery. Having established the need to choose the appropriate variety of potato for the dish being prepared, Tabitha goes on to give a cooking tip of importance. It is reproduced here with its explanatory footnote.
When [the potatoes] have boiled five minutes, pour off the hot water and replace it with cold* and half a tablespoonful of salt.
*The reason for this innovation on the general practice is, that the heart of the potato being peculiarly hard, the outside, in the ordinary course, is done long before it is softened. By chilling its exterior with cold water, the heat of the first boiling strikes to the centre of the vegetable, and as its force gradually increases when the water boils again, by the time the outside has recovered from its chilling, the equilibrium is restored, and the whole potato is evenly done.
Alan Davidson was a distinguished author and publisher, and one of the world's best-known writers on fish and fish cookery. In 1975 he retired early from the diplomatic service—after serving in, among other places, Washington, Egypt, Tunisia, and Laos, where he was British Ambassador—to pursue a fruitful second career as a food historian and food writer extraordinaire. Among his popular books are Seafood of South-East Asia, North Atlantic Seafood, and Mediterranean Seafood. In 2003, shortly before his death, he was awarded the Erasmus Prize for his contribution to European culture.
