PRESERVATION OF FOOD.

The greater part of those substances used for food can be had fresh and cheap during a short period in the year only. Commercial intercourse by land and sea, emigration, sea voyages, and expeditions for scientific purposes, the necessity of providing a supply of provisions against times of war and want-all these causes make it desirable and necessary to lay up food in store and in such a condition as will insure its preservation.

All organized substances when deprived of life undergo chemical change, by which they are in a greater or less time returned to the original chemical elements. The oxygen of the atmosphere is the first and chief cause of this dissolution, but its chemical action requires the presence of water, the temperature of which must be between 30° and 40°.

The various means in use for the artificial preservation of food, consist in the removing, either entirely or in part, the conditions which are favorable to a change. If all the methods in use in ancient or modern times, be reduced to physiological principles, it seems that the object to be attained, is either the seclusion of atmospheric air, or the r. moval of water, by drying, or keeping the substance in a temperature lower than that required for chemical change. Those articles whose preservation has bec me a matter of great importance, are meat, eggs, milk and vegetables.

PRESERVATION OF MEAT.

The surest method of preserving meat is a perfect seclusion of the air. Inclosing meat, after the method of Appent, in tin boxes, has been proved by many experiments as perfectly accomplishing the object. This method is as follows: Animal substances which have been well cooked are put in cylindrical tin boxes, which are filled almost to the brim; the lid, which has a small hole in it, is then soldered on. Through the hole in the lid the remainder of the can is filled with broth, and then this hole is closed. The boxes are now heated in a bath of salt water above the boiling point. If the box is not perfectly tight, the small bubbles will escape, thus indicating the defective spots, which are immediately closed. The boiling is continued for half an hour to one hour, according to the size of the boxes, and by it the oxygen remaining in the can is formed by combination into carbonic acid, and thus rendered harmless. After this process, the meat is not likely to spoil. It is, however, subjected to still another test, by being heated to a temperature of 30° R. for some time. If by this, decomposition takes place, it is

known by the development of gas, in consequence of which the bottom will become a little convex, while on the other hand the pressure of the outside air should make it a litle concave. Having passed through this test, no further danger of decomposition need be apprehended

Long sea voyages have proved this method of Appert's to be a very excellent one; and the preparation of animal food by this method has become an extensive branch of business. The firm of Gamble & Co., of London, presented at the World's Fair, in 1851, some boxes of food prepared in 1813, the contents of which were perfectly preserved. A portion of the boxes preserved at that time, which contained boiled mutton, taken by the Expedition to the Polar Regions in 1824, were thrown into the sea from the wreck of the Fury, in Prince Regent's Bay, 72° 47' N. Lat., 19° 40′ W. Long., and found in a state of perfect preservation by Capt. J. Ross in 1849.

The top of the box is fastened by a rim of tin which is easily torn off, thus facilitating the opening of the box which might otherwise be difficult.

In this connection we may state that all sea voyagers who had occasion to test this food preserved by Appert's method, assert that this food became unpleasant, having the taste of "medicine," and that this at length became so disgustful that they returned to salted meat.

The methods of preserving animal food, based on Appert's principle, adopted by Fastier and Willanmez, have attracted much attention of late years on account of the interest manifested in them by the Emperor Napoleon and the French government. From the reports of the commissioners appointed by the Imperial Department of the Navy and by the Admiralty of Great Britain, to investigate the conserves of Fastier, we learn that boxes which had been filled a year or more, opened in Brazil, on the Senegal, and other points, proved perfectly fresh and excellent in every respect. In general, Fastier's method resembles Apper's, but he contrives to exper all the air, even from boxes containing 100 lbs. of meat; while by Appert's method, some air may easily remain, especially in the hollow bones of poultry. Fastier proceeds in the following manner: When the meat has been put into the box, a lid having a small hole is soldered on; through this hole the vapors escape by boiling. While the vapor is still escaping, the hole is quickly closed and soldered. The box is then sprinkled with cold water, which causes the vapor contained to condense, thus creating a vacuum into which whatever air may yet be contained in the bones and meat, escapes. After some time the lid is removed, and the boiling repeated until the last particle of air and vapor is expelled, and the aperture again closed. Thick tin should be used in manufacturing the boxes, especially large ones.

More recently, Nasmyth has modified Appert's method in the following manner: The meat is placed in boxes in the usual manner, but through the lid a small tube is inserted; through this tube a small quantity of alcohol is put into every box. The boxes are then heated as before, and the vapor of alcohol expels the air from the boxes. This process is continued till the vapor from the tube will ignite by contact with a flame, and then the boxes are shut. We can

not decide upon the merits of this process. It is possible that the vapor of alcohol remaining in the box may unite with the remaining oxygen, to form aldehyde, a very interesting compound, discovered by Prof. Liebig, about twenty-five years ago. Baron Dumas, the greatest living French chemist, said, more than ten years since: "It is very possible that aldehyde is destined to be the important agent in preserving food. It absorbs oxygen and changes to vinegar, and thus acts doubly as a preservative." This significant remark has hitherto failed to attract the attention of scientific experimenters, but from the above method we find that it may have been accidentally employed. Chemistry teaches that most of the volatile oils found in the vegetable kingdom, consists either of peculiar aldehydes, or substances which, like aldehydes, are capable of combining with oxygen. When poultry are preserved for a distant market by elderberries, we may consider this but a modification of Dumas' proposition, as the etherial oil of elderberries, in the form of aldehyde, combines with the oxyen.

The process of Willanmez differs from the above by the use of glass vessels, a trio dilator, and the manner of inserting the corks. The dilator is a strip of tin bent in the shape of a spout, which is inserted into the mouth of the vessel while the operation of filling is going on, and which serves the purpose of the tin tube of the former method. The food is placed in the jar, and the superfices filled with broth or salt water. The bottles are then placed on a perforated wooden shelf, which is fixed in a kettle. This kettle is filled with a mixture of ten parts water, two parts kitchen salt, and two parts syrup. This mixture does not boil until heated to a temperature of 108 C. This is heated to boiling, and in this bath the bottles remain for an hour, when the corks, made air-tight with wax, are inserted. The bottles are then placed in the corking-press, the dilator removed, the corks pressed firmly in, and the bottles allowed to cool.

Another method, based upon the seclusion of air, has been proposed by Warrington, to prepare the flesh of the Amer can buffalo for the European market. He pours plaster of Paris over the meat, and saturates this with tallow. This or a similar method was proposed by Dr. Arcet, thirty years ago, and has lately reappeared at Paris, which is, to inclose meat in gelatine. Niepce de St. Victor, a photographer, claims to have preserved fishes in this manner for several years. This will suffice for the methods of preserving meat by deoxidation; but we have stated that meat might be preserved by depriving it of the water in its composition. The Indians of North America preserve the meat obtained in the chase by cutting it into small strips and drying. This process is called "jerking," and the meat so prepared is called "pemican." This process has the merit of giving a large amount of nutritive matter in a small space; still as the labor is great, and time required in drying long, it would not be profitable for foreign exportation; and besides, meat cut into so small slices is hardly fit for culinary purposes.

The preparation called meat biscuit is one of great importance. It is an invention of Gail Borden, who has established a factory at Galveston, Texas, where the abundance of cattle afford a plentiful and cheap supply of material. It is

claimed that one pound of this biscuit contains as much nutricious matter as five pounds of fresh beef. It is well adapted to expeditions through wilds and deserts, and sea voyages, and is much used in expeditions against the Indians.

M. Boussingault has presented to the Academy of Sciences at Paris, a report on the "meat biscuit" manufactured by Callamand, of Paris. According to his report, the preparation of this article consists of three operations: 1. The preparation of the broth. 2. The manufacture of the dough. 3. The baking of the biscuit.

In preparing the broth, 51 pounds of beef are boiled for 4 hours with 24 quarts of water, 20 pounds of vegetables, such as carrots, turnips, garlic, etc., and the necessary spices, as nutmegs, cloves, pepper, etc. The bones are then removed, and the meat cut into small pieces, and again boiled in the broth for 14 hours. By this time the whole is reduced to a pulp, in which half a pound of rock candy is dissolved, which is considered a preserving agent. In this way 11 quarts of a very concentrated broth are obtained, containing all the soluble substance of 44 pounds of beef, 7 pounds being lost in bones, sinew, etc.

In preparing the dough, the 11 quarts of broth are well mixed with 100 pounds of flour. The dough thus formed is cut in biscuits, which are baked in an oven for 1 hours. When cool they weigh 180 pounds. The composition of this biscuit is as follows:

The commissioners appointed by the Paris Academy of Sciences to examine this biscuit, boiled one of them for fifteen or twenty minutes, and obtained a soup similar to that made by soaking common biscuit in rich broth. Thus a substan. tial and tolerably palatable fo d may be made, though the commissioners believed that the amount of nutrim nt was not as great as in the same quantity of fresh beef, as by the boiling some of the nutritive elements had escaped.

A well known method of preserving meat by extracting the water, is by pickling with salt, which absorbs the water, at the same time penetrating the tissues of the meat. In pickling, the meat is well rubbed with sal', and after a few days it is pressed in a press, and the operation of rubbing repeated. The meat is then packed in barrels and brine poured over it. Generally saltpetre is used with the salt, as it contributes to the preservation of the meat and imparts a fresh hue.

The opinion that the brine exracts only the brine from the meat is erroneous. Liebig, whose careful examinations of meat and its constituents, made in 1847, should be gratefully acknowledged, found that from one-third to one-half the

elements of the meat were absorbed, and consequently the brine contains all the elements of both, and thus the composition of the meat is changed more by pickling than by boiling. In boiling, the albumen remains in the meat, but in pickling it is removed by the brine. Various other substances are also removed, thus destroying much of the power of the food, and producing such changes as may positively render it unhealthy. The scurvy which afflicts sailors is probably caused by their diet of salt meat.

A large quantity of pickled meat, prepared in America, is used in France. In 1856 M. Girardin instituted a series of comparisons, by which he was enabled to determine the amount of nutriment dissolved in the brine. The following is an average statement of their comparisons:

This proves that pickling in this manner is a very defective process for preserving, and it is very desirable that some other process should be discovered by which large quantities of meat may be preserved for transportation. The proposition to use sugar instead of salt, in order that the brine may also be used, is worthy of attention, but the process proposed by Underwood, of Manchester, is founded on a misconception of the process of nutrition. He recommends the use of a solution of argillaceous and acid clays, which have been successfully used in the preparation of anatomical specimens; but this preparation consists in changing animal fibre into leather, which renders it unfit for food.

The curing of meat by smoking has not yet been exactly demonstrated upon scientific principles. The warmth induced causes a drying of the meat, and the creosote, discovered to exist in smoke, coagulates the albuminous principles, and renders them insoluble. Besides these, it is probable that ligneous acid and other constituents of smoke perform important though uncertain parts. Although smoked meat will not compare with fresh in nutritive substance, still smoked meat is far preferable to that pickled by salt, because by smoking none of the constituents of the meat are lost. But whether the change caused by smoking does not lessen the nutritive power of meat, is a question yet to be determined by chemistry and physiology.

Vinegar, which we may now obtain so cheaply, is a valuable agent for preserv ing meat for some length of time, if the air is excluded from it; and sulphuric acid was some time ago recommended by Braconnet, and more recently by Robert.

A low temperature is one of the best agents of preservation. Meat kept in