Popular Science Monthly/Volume 23/July 1883/The Chemistry of Cookery II
|THE CHEMISTRY OF COOKERY.|
IV.—ALBUMEN AND ITS CHANGES.
LET us now make practical application of the laws of albumen coagulation that were demonstrated in the test-tube experiment. The non-professional student may do this at the breakfast fireside. The apparatus required is a saucepan large enough for boiling a pint of water—the materials two eggs.
Cook the first in the orthodox manner by keeping it in boiling water three and a half minutes. Then place the second 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 scientific 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 minutes or more.
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 for half an hour; in fact, the perfection of cooking, according to my experience (I always cook my own eggs when I have the opportunity and can spare the time), is attained when kept at 160 about twenty minutes. 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 have just made the following experiment: At 10.30 p. m. I placed a new-laid egg in a covered stone-ware 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°, that 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 similar result as regards the state of the egg.
This brings out a fact hitherto unknown to either cooks or chemists, viz., 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 the action of the other constituents on the albumen, requires further research to determine.
When eggs are cooked in the ordinary way, the three and a half 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, etc., are cooked as the eggs were in my hat-case.
Albumen exists in flesh as one of its juices, rather than in a definitely organized condition. It is distributed between the fibers 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 Lilliput were not more definitely divided than are certain cookery authorities on this question in reference to fish. I refer to the two which are practically consulted in my own household, that by Mrs. Beeton, and some sheet tablets hanging in the kitchen. Mrs. Beeton says pour cold water on the fish, the tablets say immerse in hot water.
Confining our attention at present to the albumen, what must happen if the fish or flesh is put in cold water, which is gradually heated? Obviously a loss of albumen by exudation and diffusion through the water, especially in the case of sliced fish or of meat exposing much surface of fibers cut across. It is also evident that such loss of albumen will be shown by its coagulation when the water is sufficiently heated.
Practical readers will at once recognize in the "scum" which rises to the surface of the boiling water, and in the milkiness that is more or less diffused throughout it, the evidence of such loss of albumen. This loss indicates the desirability of plunging the fish or flesh at once into water hot enough to immediately coagulate the superficial albumen, and thereby plug the pores through which the inner albuminous juice otherwise exudes.
But this is not all. There are other juices besides the albumen, and these are the most important of the flavoring constituents, and, with the other constituents of animal food, have great nutritive value; so much so, that animal food is quite tasteless and almost worthless without them. I have laid especial emphasis on the above qualification, lest the reader should be led into an error originated by the bone-soup committee of the French Academy, and propagated widely by Liebig—that of regarding these juices as a concentrated nutriment when taken alone.
They constitute collectively the extraction carnis, which, with the addition of more or less of gelatine (the less the better), is commonly sold as Liebig's "Extract of Meat." It is prepared by simply mincing lean meat, exposing it to the action of cold water, and then evaporating down the solution of extract thus obtained.
I shall return to this on reaching the subjects of clear soups and beef-tea, at present merely adding, as evidence of the importance of retaining these juices in cooked meat, that the extracts of beef, mutton, and pork may be distinguished by their specific flavors. Some "Extract of Kangaroo," sent to me many years ago from Australia by the Ramornie Company, made a soup that was curiously different in flavor from the other extract similarly prepared by the same company. Epicures pronounced it very choice and "gamy." When these juices are removed from the meat, mutton, beef, pork, etc., the remaining solids are all alike, so far as the palate alone can distinguish.
Let us now apply these principles practically to the case of a leg of mutton. First, in order to seal the pores, the meat should be put into boiling water; the water should be kept boiling for five or ten minutes. A coating of firmly-coagulated albumen will thus envelop the joint. Now, instead of boiling or "simmering" the water, set the saucepan aside, where the water will retain a temperature of about 180°, or 32° below the boiling-point. Continue this about half as long again, or double the usual time given in the cookery-books for boiling a leg of mutton, and try the effect. It will be analogous to that of the egg cooked on the same principles, and appreciated accordingly.
The usual addition of salt to the water is very desirable. It has a threefold action: first, it directly acts on the superficial albumen with coagulating effect; second, it slightly raises the boiling-point of the water; and, third, by increasing the density of the water, the "exosmosis," or oozing out of the juices, is less active. These actions are slight, but all co-operate in keeping in the juices.
I should add that a leg of mutton for boiling should be fresh, and not "hung" as for roasting. The reasons for this hereafter.
"Please, mum, the fish would break to pieces," would be the probable reply of the unscientific cook, to whom her mistress had suggested the desirability of cooking fish in accordance with the principles expounded in my last. Many kinds of fish would thus break if the popular notions of "boiling" were carried out, and the fish suddenly immersed in water that was agitated by the act of ebullition. But this difficulty vanishes when the true theory of cookery is understood and practically applied by cooking the fish from beginning to end without ever boiling the water at all.
In the case of the leg of mutton, chosen as a previous example, the plunging in boiling water and maintenance of boiling-point for a few minutes was unobjectionable, as the most effectual means of obtaining the firm coagulation of a superficial layer of albumen; but, in the case of fragile fish, this advantage can only be obtained in a minor degree by using water just below the boiling-point, for the breaking of the fish by the agitation of the boiling water does more than merely disfigure it when served; it opens outlets to the juices, and thereby depreciates the flavor, besides sacrificing some of the nutritious albumen.
To demonstrate this experimentally, take two equal slices from the same salmon, cook one according to Mrs. Beeton and other orthodox authorities by putting it into cold water, or pouring cold water over it, then heating up to the boiling-point. Cook the other slice by putting it into water nearly boiling (about 200° Fahr.), and keeping it at about 180° to 200°, but never boiling at all. Then dish up, examine, and taste. The second will be found to have retained more of its proper salmon color and flavor, the first will be paler and more like cod, or other white fish, owing to the exosmosis or oozing out of its characteristic juices.
I was surprised, and at first considerably puzzled, at what I saw of salmon-cooking in Norway. As this fish is so abundant there (two cents per pound would be regarded as a high price in the Tellemark), I naturally supposed that large experience, operating by natural selection, would have evolved the best method of cooking it, but found that, not only in the farm-houses of the interior, but at such hotels as the Victoria, in Christiania, the usual cookery was effected by cutting the fish into small pieces and soddening it in water in such wise that it came to table almost colorless, and with merely a faint suggestion of what we prize as the rich flavor of salmon. A few months' experience and a little reflection solved the problem. Salmon is so rich, and has so special a flavor, that when daily eaten it soon palls on the palate. Everybody has heard the old story of the clause in the indentures of the Aberdeen apprentices, binding the masters not to feed the boys on salmon more frequently than twice a week. If the story is not true it ought to be, for salmon every day would have the same effect as the daily breakfasts of boiled fat pork and dumplings on the voracious hero of another story.
By boiling out the rich oil of the salmon, the Norwegian reduces it nearly to the condition of codfish, concerning which I learned a curious fact from the two old Doggerbank fishermen with whom I had a long sailing-cruise from the Golden Horn to the Thames. They agreed in stating that codfish is like bread, that they and all their mates lived upon it (and sea-biscuits) day after day for months together, and never tired, while richer fish ultimately became repulsive if eaten daily. This statement was elicited by an immediate experience. We were in the Mediterranean, where the bonetta was very abundant, and every morning and evening I amused myself by spearing them from the martingale of the schooner, and so successfully that all hands (or rather mouths) were abundantly supplied with this delicious, dark-fleshed, full-blooded, and high-flavored fish. I began by making three meals a day on it, and at the end of about a week was glad to return to the ordinary ship's fare of salt-junk and chickens.
This is not exactly a digression, seeing that the philosophy of the appetite is fundamental to that of cookery. A healthy, unvitiated appetite is an index to the requirements of nutrition. Other illustrations of this will be presented as we proceed.
Another important constituent of animal food is gelatin or gelatine. It constitutes a large proportion of the whole hulk of the animal; it is, in fact, the main constituent of the animal tissues, the walls of the cells of which animals are built up being composed of gelatin. I will not here discuss the question of whether Haller's remark, "Dimidiurn corporis kuniani gluten est" ("Half of the human body is gelatin"), should or should not now, as Lehmann says, "be modified to the assertion that half of the solid parts of the animal body are convertible, by boiling with water, into gelatin." Lehmann and others give the name of "glutin" to the component of the animal tissue as it exists there, and gelatin to it when acted upon by boiling water. Others indicate this difference by naming the first "gelatin," and the second "gelatine."
The difference upon which these distinctions are based is directly connected with my present subject, as it is just the difference between the raw and the cooked material, which, as we shall presently see, consists mainly in solubility.
Even the original or raw gelatine varies materially in this respect. There is a decidedly practical difference between the solubility of the cell-walls of a young chicken and those of an old hen. The pleasant fiction which describes all the pretty gelatine preparations of the table as "calf's-foot jelly," is founded on the greater solubility of the juvenile hoof, as compared with that of the adult ox or horse, or to the parings of hides about to be used by the tanner. All these produce gelatine by boiling, the calves' feet with comparatively little boiling.
Besides these differences there are decided varieties, or, I might say, species of gelatine, having slight differences of chemical composition and chemical relations. There is chondrine, or cartilage gelatine, which is obtained by boiling the cartilages of the ribs, larynx, or joints for eighteen or twenty hours in water. Then there is fibroine, obtained by boiling spiders' webs and the silk of silk-worms or other caterpillars. These exist as a liquid inside the animal, which solidifies on exposure. The fibers of sponge contain this modification of gelatine.
Another kind is chitine, which constituted the animal food of St. John the Baptist, when he fed upon locusts and wild honey. It is the basis of the bodily structure of insects; of the spiral tubes which permeate them throughout, and are so wonderfully displayed when we examine insect anatomy by aid of the microscope, also of their intestinal canal, their external skeleton, scales, hairs, etc. It similarly forms the true skeleton and bodily framework of crabs, lobsters, shrimps, and other Crustacea, bearing the same relation to their shells, muscles, etc., that ordinary gelatine does to the bones and softer tissues of the vertebrata; it is "the bone of their bones, and the flesh of their flesh." It is obtainable by boiling these creatures down, but is more difficult of solution than the ordinary gelatine of beef, mutton, fish, and poultry. To this difficulty of solution in the stomach is to be attributed, I suspect, the nightmare that follows lobster-suppers.
I once had an experience of the edibility of the shells of a crustacean. When traveling, I always continue the pursuit of knowledge in restaurants by ordering anything that appears on the bill of fare that I have never heard of before, or can not translate or pronounce. At a Neapolitan restaurant, I found "Gambers di mare" on the carta, which I translated "Leggy things of the sea," or sea-creepers, and ordered them accordingly. They proved to be shrimps fried in their shells, and were very delicious—like white-bait, but richer. The chitine of the shells was thus cooked to crispness, and no evil consequences followed. If reduced to locusts, I should, if possible, cook them in the same manner, and, as they have similar chemical composition, they would doubtless be equally good.
Should any epicurean reader desire to try this dish (the shrimps, I mean), he should fry them as they come from the sea, not as they are sold by the fishmonger, these being already boiled in salt-water (usually in sea-water) by the shrimpers who catch them, the chitin being indurated thereby.
The introduction of fried and tinned locust as an epicurean delicacy would be a boon to suffering humanity, by supplying industrial compensation to the inhabitants of districts subject to periodical plagues of locust invasion. The idea of eating them appears repulsive at first, so would that of eating such creepy-crawly things as shrimps, if no adventurous hero had made the first exemplary experiment. Chitine is chitine, whether elaborated on the land or secreted in the sea. The vegetarian locust and the cicala are free from the pungent essential oils of the really unpleasant cockchafer.
Those who are disposed to bow too implicitly to mere authority in scientific matters will do well to study the history and the treatment which gelatine has received from some of the highest of these authorities. Our grandmothers believed it to be highly nutritious, prepared it in the form of jellies for invalids, and estimated the nutritive value of their soups by the consistency of the jelly which they formed on cooling, which thickness is due to the gelatine they contain. Isinglass, which is simply the swim-bladder of the sturgeon and similar fishes cut into shreds, was especially esteemed, and sold at high prices. This is the purest natural form of gelatine.
Everybody believed that the callipash and callipee of the alderman's turtle-soup contributed largely to his proverbial girth, and those who could not afford to pay for the gelatine of the reptile made mock turtle from the gelatinous tissues of calves'-head and pigs'-feet. The delicacies of the Orient, the edible birds'-nests, the sea-slugs, etc., so highly esteemed for their nutritious properties, are varieties of gelatine.
About fifty or sixty years ago the French Academy of Sciences appointed a bone-soup commission, consisting of some of the most eminent savants of the period. They worked for above ten years upon the problem submitted to them, that of determining whether or not the soup made by boiling bones until only their mineral matter remained solid, is or is not a nutritious food for the inmates of hospitals, etc. In the voluminous report which they ultimately submitted to the Academy, they decided in the negative.
Baron Liebig became the popular exponent of their conclusions, and vigorously denounced gelatine, as not merely a worthless article of food, but as loading the system with material that demands wasteful effort for its removal.
The Academicians fed dogs on gelatine alone, and found that they speedily lost flesh, and ultimately died of starvation. A multitude of similar experiments showed that gelatine alone would not support animal life, and hence the conclusion that pure gelatine is worthless as an article of food, and that ordinary soups containing gelatine owed their nutritive value to their other constituents. According to the above named report and the statements of Liebig, the following, which I find on a wrapper of Liebig's "Extract of Meat," is justifiable: "This extract of meat differs essentially from the gelatinous product obtained from tendons and muscular fiber, inasmuch as it contains eighty per cent of nutritive matter, while the other contains four or five per cent." Here the four or five per cent allowed to exist in the "gelatinous product" (i. e., ordinary kitchen stock or glaze) is attributed to the constituents it contains over and above the pure gelatine.
Subsequent experiments, however, have refuted these conclusions. I must not be tempted to describe them in detail, but only to state the general results, which are, that while animals fed on gelatine-soup, formed into a soft paste with bread, lost flesh and strength rapidly, they recovered their original weight when to this same food only a very small quantity of the sapid and odorous principles of meat were added. Thus, in the experiments of Messrs. Edwards and Balzac, a young dog that had ceased growing, and had lost one fifth of its original weight when fed on the bread and gelatine for thirty days, was next supplied with the same food, but to which was added, twice a day, only two tablespoonfuls of soup made from horse-flesh. There was an increase of weight on the first day, and "in twenty-three days the dog had gained considerably more than its original weight, and was in the enjoyment of vigorous health and strength."
All this difference was due to the savory constituents of the four tablespoonfuls of meat-soup, which soup contained the juices of the flesh, to which, as already stated, its flavor is due.
The inferences drawn by M. Edwards from the whole of his experiments are the following: "1. That gelatine alone is insufficient for alimentation. 2. That, although insufficient, it is not unwholesome. 3. That gelatine contributes to alimentation, and is sufficient to sustain it when it is mixed with a due proportion of other products which would themselves prove insufficient if given alone. 4. That gelatine extracted from bones, being identical with that extracted from other parts—and bones being richer in gelatine than other tissues, and able to afford two thirds of their weight of it—there is an incontestable advantage in making them serve for nutrition in the form of soup, jellies, paste, etc., always, however, taking care to provide a proper admixture of the other principles in which the gelatine-soup is defective. 5. That to render gelatine-soup equal in nutritive and digestible qualities to that prepared from meat alone, it is sufficient to mix one fourth of meat-soup with three fourths of gelatine-soup; and that, in fact, no difference is perceptible between soup thus prepared and that made solely from meat. 6. That in preparing soup in this way, the great advantage remains that, while the soup itself is equally nourishing with meat-soup, three fourths of the meat which would be requisite for the latter by the common process of making soup are saved and made useful in another way—as by roasting, etc. 7. That jellies ought always to be associated with some other principles to render them both nutritive and digestible."
The reader may make a very simple experiment on himself by preparing first a pure gelatine-soup from isinglass, or the prepared gelatine commonly sold, and trying to make a meal of this with bread alone. Its insipidity will be evident with the first spoonful. If he perseveres, it will become not merely insipid, but positively repulsive; and, should he struggle through one meal and then another, without any other food between, he will find it, in the course of time (varying with constitution and previous alimentation), positively nauseous.
Let him now add to it some of Liebig's "Extract of Meat," and he will at once perceive the difference. Here the natural appetite foreshadows the result of continuing the experiment, and points the way to correcting the errors of the Academicians and Baron Liebig. The jellies that we take at evening parties, or the jujubes used as sweetmeats, are flavored with something positive. I have tasted "Blue Ribbon" jellies that were wretchedly insipid. This was not merely owing to the absence of alcohol, of which very little can remain in such preparations, but rather to the absence of the flavoring ingredients of the sherry. The Rahat Lakoum, or "lumps of delight," sold in the streets of Constantinople, is gelatine flavored with the unfermented juices of fruit. A privileged visit which I once made to the monster kitchen of the Old Seraglio of his Majesty the Sultan (at Stamboul) lives perpetually in my memory, so sweetly, so vividly, and so gratefully, that when I find myself defending the Turk against the Russian and all his other enemies, my conscience sometimes inquires whether those lumps of delight prepared for the Sultana by his Highness the Grand Confectioner, and presented to me by him as a sample of his masterpiece, may, or may not, have ever after influenced my politics. It was gelatine glorified, once tasted never to be forgotten.
It would seem that gelatine alone, although containing the elements required for nutrition, requires something more to render it digestible. We shall probably be not far from the truth if we picture it to the mind as something too smooth, too neutral, too inert, to set the digestive organs at work, and that it therefore requires the addition of a decidedly sapid something that shall make these organs act. I believe that the proper function of the palate is to determine our selection of such materials; that its activity is in direct sympathy with that of all the digestive organs; and that, if we carefully avoid the vitiation of our natural appetites, we have in our mouths, and the nervous apparatus connected therewith, a laboratory that is capable of supplying us with information concerning some of the chemical relations of food which is beyond the grasp of the analytical machinery of the ablest of our scientific chemists.
There is another element of flesh so intimately connected with gelatine and so much like it, that I must describe its properties before going further into the subject of practical cookery of animal food. I refer to fibrine, which will form the subject of my next paper.—Knowledge.
- London, "Nouveaux Élémens d'Hygiène," second edition, vol. ii, p. 73.