We have only space briefly to describe some of the more prominent of the processes which have been devised for the preservation of meat by excluding atmospheric air.
Mr Tallerman, a large importer of Australian meat, stated in evidence before the Food Committee of the Society of Arts, in May, 1870, that in the preservation of the meat he sent over to this country he had recourse to a very old practice, which was that of packing the joints in fat, the meat being previously salted or cured. Instead of the meat being packed in brine, the casks with the meat are filled up with melted fat.
In Mr Warrington’s patent, which dates from 1846, it is proposed that animal substances shall be preserved by enveloping them in a layer of glue, gelatin, or concentrated meat gravy, or otherwise by dipping them in warm solutions of such substances, or by wrapping them in waterproof cloth, or by
covering them with caoutchouc, gutta percha, or varnish, or thin cream of plaster of Paris, which when set was saturated with melted suet, wax, or stearin.
The patent of Prof. Redwood, which resembles Mr Warrington’s in seeking to exclude atmospheric air by surrounding the meat with an impervious substance, claimed the use of paraffin for this purpose, the paraffin being afterwards coated with a mixture of gelatin and treacle, or gelatin and glycerin. The paraffin is easily removed from the meat by plunging this latter into boiling water, which dissolves the outer coating of gelatin mixture, and at the same time melts the paraffin and liberates the enclosed joint.
Messrs Jones and Trevethick’s patent consisted in exhausting of air the vessel containing the meat, then forcing into it a mixture of nitrogen and sulphurous acids, and subsequently soldering the apertures. Dr Letheby says meat, fish, and poultry preserved in this manner have been found good after seven or eight years; and specimens of them were exhibited in the London Exhibition of 1862.
The removal, however, of atmospheric air from the vessels containing the meat it is designed to preserve is now principally accomplished by means of steam. The germ of this idea originated with M. Pierre Antonie Angilbert more than half a century ago, but the modification of Angilbert’s process, which in principle is that generally adopted by the importers of Australian and South American cooked meat, as well as by the English preparers of the article, originated with Messrs Goldner and Wertheimer, nearly forty years since, and, briefly, is as follows:—The freshly killed meat is placed in tins, with a certain quantity of cold water. The tins and their contents are then securely soldered down, with the exception of a small opening not larger than a pin-hole, which is left in the lid. The tins are next placed in a bath of chloride of calcium, the effect of which is to heat the water in them up to the boiling point, and after a certain time to more or less cook the meat contained in them. When the meat is thought to be sufficiently cooked, and whilst the steam arising from the boiling water is escaping from the aperture, this last is carefully soldered down, the steam not only having driven out all the atmospheric air from the vessel, but in the act of escaping having prevented the ingress of any from without. To still further guard against the entrance of air, the tins are covered over with a thick coating of paint.
Previously to their being allowed to leave the preserving works they are tested by being placed for some time in an apartment in which the temperature is sufficiently high to set up putrefactive action in the meat if any air has been left in the tins, the evidence of which would be the bulging out of the tins, owing to the liberation of certain gaseous products of decomposition. When no distension from inside
takes place, the result is considered satisfactory, and the vessels are regarded as properly and hermetically sealed. In some cases the vessels, instead of being heated in a bath of chloride of calcium, are exposed to the action of steam. If the operation be successfully performed, the meat so prepared will keep perfectly good avid sound for years.
Mr Richard Jones effects the removal of the air from the vessels containing the meat as follows:—The meat is put into the tins and entirely soldered up, with the exception of a small tube about the size of a quill, which is soldered on the top of the tin. This tube is placed in connection with a vacuum chamber, and the air exhausted from the tin by means of it. In cooking the meat he also employs a chloride of calcium bath.