THE CHEMISTEY OF COOKEKY.

Tuapeka Times, Issue 851, 30 June 1883, Page 2 (Supplement)

THE CHEMISTEY OF COOKEKY.

BY W. MATTEATJ WILLIAMS. in. — Cooking Under Water.

Next to the boiling of water for its own sake, as treated in my last, comes the boiling of water as a medium for the cooking of other things. Here, at the outset, I have to correct an error of language whioh, as too often happens, leads by continual suggestion to false ideas. When we speak of " boiled beef," " boiled mutton," " boiled eggs," " boiled potatoes," we talk nonsense ; we are not merely using an, elliptical expression, as when we say " the kettle boils," which we all understand to mean the contents of the kettle, but we are expounding a false theory of what ha 3 happened to the beef, &c— as false as though we should describe the material of the kettle that has held boiling water as boiled copper or boiled iron. No boiling of the food takes place in any such cases as the abovenamed—it is merely heated by impression in boiling water ; the changes that actually take place in the food are essentially different from those of ebullition. Even the water contained in the meat is not boiled in ordinary cases, as its boiling point is higher than that of the surrounding water, owing to the salts it holds in solution.

Thus, as a matter of chemical fact, a " boiled leg of mutton" is one that has been cooked, but not boiled ; while a roasted leg of mutton is one that has been partially boiled. Much of the constituent water of flesh is boiled out, fairly driven away as vapour during roasting or baking, and the fat on its surface is also boiled, and, more or less, dissociated into its chemical elements, carbon and water, as shown by the browning, due to the separated carbon.

As I shall presently show, this verbal explanation is no mere verbal quibble, but it involves important practical applications. An enormous waste of precious fuel is perpetrated every day, throughout the whole length and breadth of Britain and other countries where English cookery prevails, on account of the almost universal ignorance of the philosophy of the so-called boiling of food. When it is fairly understood that the meat is not to be boiled, but is merely to be warmed by immersion in water raised to a maximum temperature of 212 deg, and when it is further understood Jthat water cannot (under ordinary atmospheric pressure) be raised to a higher temperature than 212 deg by any amount of violent boiling, the popular distinction between " simmering" and boiling, which is so obstinately maintained as a kitchen superstition, is demolished.

The experiment described in my last showed that immediately the bubbles of steam reach the surface of the water and break there— that is, when simmering commences— the thermometer reaches the boiling point, and that however violently the boiling may afterwards occur, the thermometer rises no higher. Therefore, as a medium for heating the substances to be cooked, simmering water is just as effective as " walloping" water. There are exceptional operations of cookery, to be described hereafter, wherein useful mechanical work is done by violent boiling : but in all ordinary cookery, simmering is just as effective. The heat that is applied to do more than the smallest degree of simmering is simply wasted in converting water into useless steam. The amount of such waste may be easily estimated. To raise a given quantity of water from the freezing to the boiling point demands an amount of heat represented by 180 deg in Fahrenheit's thermometer, or 100 deg Centigrade. To convert this into steam, 990 deg Fah. or 559 deg Cent, is necessaryjust five and a-half times as much.

On a properly-constructed hot-plate or sand-bath, a dozen saucepans may be kept at the true cooking temperature, with an expenditure of fuel commonly employed in England to " boil " one saucepan. In the great majority of so-called boiling operations, even simmering is unnecessary. Not only is a " boiled leg of mutton" not itself boiled, but even the water in which it is cooked should not be kept boiling, as we shall presently see. In order to illustrate some of the changes which take place in the cooking of animal food, I will first take the simple case of cooking an egg by means of hot water. These changes are in this case easily visible and very simple, although the egg itself contains all the materials of a complete animal. Bones, muscles, viscera, brain, nerves, and feathers of the chicken— all are produced within the shell, nothing being added, and little or nothing taken away.

When we open a raw egg, we find, enveloped in a stoutish membrane, a quantity of glairy, slimy, viscous, colourless fluid, which, as everybody now knows, is called albumen, a Latin translation of its common name, " tlie lohite." Within the white of the egg is the yolk, largely composed of that same albumen, but with other constituents added — notably a peculiar oil. At present I will only consider the changes which cookery effects on the main constituent of the egg, merely adding that this same albumen is one of the most important, if not the, one most material of animal food, and is represented by a corresponding nutritious constituent in vegetables.

We all know that when an egg has been immersed during a few minutes in boiling water, the colourless, slimy liquid is converted into the white solid to which it owes its name. This coagulation of albumen is one of the most decided and best understood changes effected by cookery, and therefore demands especial study.

Place some fresh, raw white of egg in a test-tube or other suitable glass vessel, and in the midst of it immerse the bulb of a thermometer. (Cylindrical thermometers, with the degrees marked on the glass stem, are made for such laboratory purposes.) Place thejtube containing the albumen in a vessel of water, and gradually heat this. When the albumen attains a temperature of about 134 deg Fahr., white fibres will begin to appear within it ; these will increase until about 160 deg is attained, when the whole mass will become white and nearly opaque. It is now coagulated, and may be called solid. Now examine some of the result, and you will find that the albumen thus only just coagulated is a tender, delicate, jelly-like substance, having every appearance to sight, touch, and taste of being easily digestible. This is the case.

Having^ settled these points, proceed with the experiment by heating the remainder of the albumen (or a new sample) up to 212 deg. and keeping it for awhile at this temperature. It will dry, shrink, and become horny. If the heat is carried a little further, it becomes converted into a substance which is so hard and tough that a valuable cement is obtained by simply smearing the edges of the article to be cemented with white of egg, and then heating it to a little above 212 deg. *

* "Egg-cement," made by thickening white of egg with finely-powdered quicklime, has long been used for mending alabaster, marble, &c. For joining fragments of fossils and mineralogical specimens, it will be found very useful. White of egg alone may be used, if carefully heated afterwards.

This simple experiment teaches a great deal of what is but little known concerning the philosophy, of cookery. It shows in the first place thai, "so far as the coagulation of the albumen', is concerned, the cooking temperature is not 212 deft, or that of boiling water, but IGO,' *i.c. _. 52 i|eg below it. Everybody knows the difference between a tender," juicy steak, rounded or plumed- out in the middle, and a tough, leathery abomination, that has been so cooked as to shrivel and curl 1 up. The contraction, .drying up, and hornifying of the albumen in the test-tube represents the albumen of the latter, while the tender, delicate, trembling, semi-solid that was coagulated at 160 deg, represents the albumen in the first.

But this is a digression, or rather anticipation, seeing that the grilling of a beefsteak is a problem of profound complexity that we cannot solve until we have mastered the rudiments. We have not yet determined how to practically apply the laws of albumen coagulation as discovered by ourtest-tubo experiment to the cooking of a breakfast egg.