PORK AND BACON

Evening Post, Volume CXV, Issue 62, 15 March 1933, Page 3

PORK AND BACON

PEOBLEM OF STORAGE

CARBON DIOXIDE

RESEARCH AT CAMBRIDGE

(From "The Post's" Representative.) LONDON, February 9. An interesting experiment in connection with the storage of pork ana bacon is being carried out at the Low Temperature Research Station at Cambridge. Public attention was called to this by the exhibition of sides of pork and bacon at the Empire Pork Show at Smithfield this week, when Dr. E. H. Callow was present to explain what had been done.

A pork carcass had been stored at 32deg F. in an atmosphere of carbon dioxide for 10J weeks, and. a side of mild-cured, unsmoked bacon for 18+ weeks. It must be admitted that the appearance of the meat was not attractive, but Dr. Callow maintained that the appearance was the most unsatisfactory part of the experiment. In a previous experiment the Eesearch Station stored two sides of unsmoked, mild-cured bacon for a prolonged period at SOdeg F. After 18 weeks' storage the bacon looked not more a week old, and after being smoked it was indistinguishable from fresh (smoked) bacon. Samples of the bacon were distributed for cooking and tasting tests. In every case the fat was found to be quite free from rancidity, and the only fault observed was a very slight toughness of the lean.

A carcass of pork has previously been stored at 30dcg F. for 17 weeks in an atmosphere of carbon dioxide. It was then sent by road to Smithfield Market and examined critically. One side of the carcass was removed and cut into joints. According to expert opinion, the freshly-cut surfaces were indistinguishable from those of fresh, pork. The fat was perfectly sweet and free from rancidity. This was true even of the fat exposed in the body cavity. The surfaces of lean meat which had been exposed during the storage period were, however, slightly brown. (This discoloration is due to the fact that oxyhaemoglobin, the Ted pigment of pork meat, changes to a brown pigment, methaemoglobin, in the presence of large concentrations of carbon dioxide.) There was also a faint, sour smell round the kidneys and a scarcely perceptible growth of microorganisms in the same place.. Cooking tests showed that the only differences between gas-stored and fresh pork were that the gas-stored meat was more tender and perhaps a little lacking in flavour as compared with fresh meat. A side of pork which had been stored in carbon dioxide at 32deg P. for eight weeks was converted into bacon with a considerable amount of success. There was no sign of rancidity in the fat, and the only fault found with the lean was its saltiness. ACTION OI1 CAKBON DIOXIDE. "On the purely scientific side," said Dr. Callow, "it can be claimed that the storage of bacon in carbon dioxide is highly successful, and that the storage of chilled pork in carbon dioxide is a great improvement on present-day commercial methods. Carbon dioxide acts in two ways. In the first place, it prevents, or greatly retards, the growth of micro-organisms. Carbon dioxide acts as a mild antiseptic because it is an acid, and also because of some specific property which is not yet completely understood. In the second place, carbon dioxide excludes oxygen, and thus prevents the development of rancidity in the fat, since rancidity is due to chemical changes which are caused by oxygen, "Rancidity can only be prevented in bacon fat by using practically oxygenfree atmosphere for storage. Curiously enough, the growth of micro-ovganisms prevents rancidity, possibly by removing oxygen from the fat. Thus, bacon fat becomes rancid if only 75 per cent, of carbon dioxide is used. Even with pork, the fat of which does not become rancid as readily as bacon fat, 75 per cent, of carbon dioxide is not as satisfactory as 100 per cent., although any concentration of carbon dioxide above about 25 per cent, prolongs the storage life of chilled pork to some extent by retarding the growth of micro-organ-isms. "In order to prevent Tancidity, therefore, we have used practically 100 per cent, of carbon dioxide. Storage has been, carried out in specially-designed, large metal containers from which the air has been displaced by carbon dioxide. Although, great care has been taken in the design of ihese containers, they have not been absolutely gastight, and the carbon dioxide has been renewed at weekly intervals, in order to be on the safe side. By this means, the carbon dioxide has been kept betw.een 98 per cent, to 100 per cent. THE ECONOMIC ASPECT. "The construction of larger units for gas storage on land does not appear to be much more difficult than the construction of our metal containers. Already there is a large gas store for eggs in Denmark, in which the storage rooms of steel plate (2 millimetres thick), are over 15 feet long and 10 feet wide, with a height of 9 feet. But it should be pointed out that the maintenance of complete atmospheres of a gas like carbon dioxide presents engineering difficulties of a special kind. There is no reason, however, to believe that these difficulties are insuperable. "To be a commercial success, gas storage must pay the extra costs of equipment and running out of the savings which, it makes possible. In the first place, the risks of spoilage are decreased. Secondly, higher temperatures can be used for- storage (e.g., chilling instead of freezing temperatures), and thirdly, the losses in weight due to drying out are greatly reduced. In the case of mild-cured, unsmoked bacon, gas storage is the only method, at present known, by which it can bo stored for more than about six weeks. As can be seen by this exhibit, bacon keeps remarkably well in 100 per cent, carbon dioxide at 32deg F. The colour_ is actually enhanced, no micro-organisms grow on the surface, and the fat remains free from, rancidity. If the engineer can construct suitable gas stores at a reasonable cost, this method of storage will provide a far more satisfactory way of dealing with gluts of bacon than exists at present. "The gas storage of chilled pork is not so necessary because pork can be stored in the frozen condition for very long periods. Moreover, the gas storage of pork is not yet as successful as that of bacon. The growth of microorganisms is not entirely prevented, and there is a tendency of the exposed lean surfaces of pork to turn brown. Apart from these minor defects, gas storage makes it possible to store chilled pork for much longer periods than is possible by other methods,- and if further experiments overcome the slight difficulties encountered, the gas storage of pork may well have a commercial future. "The future of gas storage for the sea-borne transport of work and bacon is somewhat more problematical. It is much more difficult to design a gastight hold than a gastight land store, and until experience has been gained on land it might be unwise to advocate the use of gas storage for thp transport of imported pork or bacon."