The Chemistry of Cookery

by W. Mattieu Williams

Cook one in the orthodox manner by keeping it in boiling water three-and-a-half minutes. Then place the other in this same boiling water; but, instead of keeping the saucepan over the fire, place it on the hearth and leave it there, with the egg in it, about ten minutes or more. A still better way of making the comparative experiment is to use, for the second egg, a water-bath, or bain-marie of the French cook—a vessel immersed in boiling, or nearly boiling water, like a glue-pot, and therefore not quite so hot as its source of heat. In this case a thermometer should be used, and the water surrounding the egg be kept at or near 180° Fahr. Time of immersion about ten or twelve minutes.

A comparison of results will show that the egg that has been cooked at a temperature of more than 30° below the boiling-point of water is tender and delicate, evenly so throughout, no part being hard while another part is semi-raw and slimy.

I said ‘ten minutes or more,’ because, when thus cooked, a prolonged exposure to the hot water does no mischief; if the temperature of 160° is not exceeded, it may remain twice as long without hardening. The 180° is above-named because the rising of the temperature of the egg itself is due to the difference between its own temperature and that of the water, and when that difference is very small, this takes place very slowly, besides which the temperature of the water is, of course, lowered in raising that of the cold egg.

In order to test this principle severely, I made the following experiment. At 10.30 P.M. I placed a new-laid egg in a covered stoneware jar, of about one-pint capacity, and filled this with boiling water; then wrapped the jar in many folds of flannel—so many that, with the egg, they filled a hat-case, in which I placed the bundle and left it there until breakfast-time next morning, ten hours later. On unrolling, I found the water cooled down to 95°; the yolk of the egg was hard, but the white only just solidified and much softer than the yolk. On repeating the experiment, and leaving the egg in its flannel coating for four hours, the temperature of the water was 123° and the egg in similar condition—the white cooked in perfection, delicately tender, but the yolk too hard. A third experiment of twelve hours, water at 200° on starting, gave a similar result as regards the state of the egg.

I thus found that the yolk coagulates firmly at a lower temperature than the white. Whether this is due to a different condition of the albumen itself or to the action of the other constituents on the albumen, requires further research to determine. The albumen of the yolk has received the name of ‘vitellin,’ and is usually described as another variety differing from that of the white, as it is differently affected by chemical reagents; but Lehmann[4] regards it as a mixture of albumen and casein, and describes experiments which justify his conclusion. The difference of the temperature of coagulation does not appear to have been observed, and I cannot understand how the admixture of casein can effect it.

When eggs are cooked in the ordinary way, the 3½ minutes’ immersion is insufficient to allow the heat to pass fully to the middle of the egg, and therefore the white is subjected to a higher temperature than the yolk. In my experiment there was time for a practically uniform diffusion of the heat throughout.

I shall describe hereafter what is called the ‘Norwegian’ cooking apparatus, wherein fowls, &c., are cooked as the eggs were in my hat-case.

Albumen exists in flesh as one of its juices, rather than in a definitely-organised condition. It is distributed between the fibres of the lean (i.e. the muscles), and it lubricates the tissues generally, besides being an important constituent of the blood itself—of that portion of the blood which remains liquid when the blood is dead—i.e. the serum. As blood is not an ordinary article of food, excepting in the form of ‘black puddings,’ its albumen need not be here considered, nor the debated question of whether its albumen is identical with the albumen of the flesh.

Existing thus in a liquid state in our ordinary flesh meats, it is liable to be wasted in the course of cookery, especially if the cook has only received the customary technical education and remains in technological ignorance.

To illustrate this, let us suppose that a leg of mutton, a slice of cod, or a piece of salmon is to be cooked in water, ‘boiled,’ as the cook says. Keeping in mind the results of the previously-described experiments on the egg-albumen, and also the fact that in its liquid state albumen is diffusible in water, the reader may now stand as scientific umpire in answering the question whether the fish or the flesh should be put in hot water at once, or in cold water, and be gradually heated. The ‘big-endians’ and the ‘little-endians’ of Liliput were not more definitely divided than are certain cookery authorities on this question in reference to fish. Referring at random to the cookery-books that come first to hand, I find them about equally divided on the question.