MEAT-PRESERVING FOR EXPORTATION.

Hawke's Bay Weekly Times, Volume 2, Issue 60, 24 February 1868, Page 49

MEAT-PRESERVING FOR EXPORTATION.

Unquestionably one of the greatest problems of the present age is that of so treating the surplus stock of the Colonies that whole carcasses and joints may be presented to the British comsumer in a state as nearly approaching that of the fresh home-killed beast as possible: It is a problem, too, which no one at all conversant with the resources of chemistry would pronounce beyond the range of possibility, or even economical probability, and we hesitate not to say that if the rewards offered by several Governments for the discovery of gold-fields had been offered for the discovery of such a process, the problem would have' long: since been satisfactorily solved; ■■■ - - ’•

For many years past a process of preserving cooked meats in air-tight tins lias been practised with a great amount of success—-in fact, amongst the treasures rescued from the wreck of the Royal George; in 1834, were some tins of this description, the contents ,’df l which, though subjected to suhmersionduringawhole generation, weje,iyet sweetandgood—the preser-

vation in such cases depending on the complete exclusion of atmospheric air, without the presence of which fermentation cannot take place. The- preserving of food by this process has become an important branch of manufacturing industry, and it produces an excellent article of diet for long sea* voyages and many other circumstances, but it has not become, nor will it ever become, a staple article of food with the “ Britisher.” It makes beyond question a good mess, but this is exactly what John Bull does not want day by day. He must have his joint of meat, and this he will not exchange for any number of tins of the preserved article. ‘ The well-established conditions of fermentation or decay (for the terms are convertible) are, first, fermentable matter; second, some, active ferment; third, the atmospheric air ; fourth, moisture ; and, fifth, a sufficient temperature. Any one of these being absent the fermentation is stayed. In the case under consideration the flesh is the fermentable matter, and it contains within itself an active ferment. There then remains the other three conditions, either of which, being abstracted, solves the problem. First,, atmospheric air. The potted meats to which allusion has been made above are preserved in this way* The flesh, being cut in small pieces is placed in tin canisters, which are soldered down, a small hole only being left in the top for the escape of steam. These are then subjected to a high degree of heat for a period more or less prolonged, which causes a great production of steam. This, rushing out of the small aperture, carries out with it all the atmospheric air, its place being supplied with aqueous vapor. When this is judged to be accomplished a drop of solder is melted over the hole and suddenly cooled, the entrance of the air being effectually stopped, and so the process of fermentation is stayed. Next, the presence of moisture has been said to be a condition. The application of this principle of counteracting this condition is seen in the case of dried provisions of various kinds, which has a somewhat extensive and useful application, especially when used together with an antiseptic ; but it does not seem calculated to answer the desired end of superseding the j oint of butcher’s meat.

Lastly, the temperature. It has long been known that no fermentation takes place at or below the temperature of the freezing point of water, and this knowledge has been turned to account in the packing of provisions in ice for transmission to distant parts, the only points to be attended to being the freshness of the article when packed, and the prevention of a rise of temperature.

So certainly successful is this principle that no limit whatever seems to be assignable to its application." It is known, in fact, that the carcasses of a pre-Adamic era have been effectually preserved in ice by nature down to our own day—such carcasses being occasionally brought down by glaciers from high northern latitudes, and being useable and used as food by dogs and men, after having been dead for thousands of years, being preserved from decay all during that period of time by the exceedingly low temperature of theijpolar regions.

What was then, for the solution of the great problend was)- the discovery of a , method by which the freshly-killed sheep and oxenof the Australian Colonies could * be at once frozen! and; kept in tfiat stale during their transmission to the home market, this iniplying of coarsest

voyage through the tropical regions, and extending over a period of three or four months.

Chemistry is at no loss for means for the production of changes of temperature ; scarcely any operation can be performed without a disturbance of that description— and solutions in general being usually attended with .a reduction of temperature, while condensation and crystallization, are as usually attended by the evolution of heat. A thermometer, for instance, taken from water of any temperature, always descends at first from the evaporation of moisture from its surface, and, as a familiar instance, a person’s hand, being dipped in water and being afterwards moved rapidly through the air, will experience a decided sensation of cold. Water, too, may he easily frozen in a bottle by keeping the exterior surface moistened with sulphuric ether—the heat necessary for its evaporation being obtained from the water, speedily reduces it to the state of ice.

The following parlor experiment, being at once easy, interesting, and instructive, may be performed by any person desiring to have a practical illustration of the remarkable facility with which ice may be procured at any time, and it will well repay the trouble attending its performance. Take two vessels of any convenient kind, one being smaller and capable of standing inside the other, leaving a space between—say, two cylinders of tin, one of 3in. and the other of in diameter, and as high as convenient; nearly fill the smaller one with water, and stand it in the larger during the solution of a mixture of equal parts of carbonate of soda and nitrate of ammonia, covering the whole with a woollen cloth during the operation. Four ounces of each of the above salts will freeze lOoz. of water during their solution, in two or three hours, and the cylinder of ice may be turned out solid on the table. The outer vessel should be well protected from the warmth of the room by a coating of flannel or wool. One of the most beautiful expert* ments in the whole range of chemistry is the freezing of carbonic acid gas. This gas is not permanently elastic, but can by pressure oh itself be compressed to the liquid state, and its freezing may be accomplished as follows—By means of a powerful condensing syringe force a large quantity of carbonic acid gas into a strong glass vessel provided with a stopcock at its upper part; as it is condensed in this vessel it will be seen to collect at the bottom like oil. If the stop-cock be then opened to give it vent it will resume its gaseous form, rushing out with violence, absorbing even its own sensible heat, and producing cold so intense that itself freezes and falls in the form of a beautiful snow. A phenomenon of a similar character may be produced with ammonia. In its dry state it exists as a gas, and like the above it may be by pressure forced to assume the liquid state, absorbing a vast amount of heat on resuming its gaseous condition, and this property it is that renders it available for the production of artificial cold, as is exemplified in the process, of the “ ice company 5 ’ of a neighboring

colony. This process, as we understand it from description in the Sydney papers, we shall endeavor to explain to the general reader in a very few words— The apparatus consists of a “ meatreceiver,” analagous in its use to the smaller of the two vessels used in our parlor experinent; a s ** liquid gas receiver,” corresponding to r the .strong glass vessel in

jearbonic acid gas, and a “ re-absorber.” itlie' meat receiver is a capacious cave .surrounded by an air-tight chamber, which communicates with the liquified gas and also' with the re-absorber by paeans of stop-cocks. A small quantity of the liquified gas being passed iftto the airtight chamber and the stopcock closed, it is in its highly com-

pressed state in contact with’ the exterior of the meat receiver, and ready for active service. On communication being opened with the re-absorber the gas expanding rushes violently into it, carrying off with it the heat from the contents of the meat receiver. The re-

gbsorber contains water which rapidly absorbs the gas, and becomes a solution of ammonia which it is ready to give off for condensation as before.

The above is sufficient to give an idea of the means used for producingthe exceedingly low temperature of the 'meat receiver, but the beautiful' arrangement by means of which the , above - circulation is- effected, and the volatilised ammonia is deprived of its

watery vapor (desiccated) and rendered fit for compression, and the water condensed from it carried by a second circulatory'system, back from the de-

siccator to the re-absorber, to be again charged with the gas it has just before

teen parted from, involves details

Which require the aid of illustrative ‘ diagrams to Explain. It is sufficient to pay that as in the grand operations of nature, there is a continued circulation of the same elements, which are combined aiid decomposed, volatilised ' and condensed, the lhotjve poweij being ; heat first applied to volatilise * the ammonia in the separator. From wbat has been said above it Will be seen that ' the principle of the invention —the compression of an Clastic fluid artificially/in order that in its re-expansion it may absorb heat from contiguous bodies-^—is not by any means new, nor of limited application, that a similar result can be effected by the use of ether, carbonic acid gas, or any of a numerous class of bodies that fulfil the requisite conditions. In the present case ammonia was chbsen on account of its affinity for ’ water, which doubtless gives it an advantage; still we regard it but as the first of a series of applications of a well established principle, in the success of which we have every confidence.