THE BELL-COLEMAN COLD AIR MACHINE In this machine the air is taken from the cooling room and subjected to a pres sure of two to three atmospheres in a compression cylinder. The air thus heated by compression is cooled by a water spray, dried by passing through a series of sieve structures and finally cooled in tubes to a temperature of 41° F. From the expansion cylinders, the air escapes into the cooling rooms at a methyl ether, sulphuric ether, sul phurous acid and ammonia, but princi pally ammonia. The principle on which these machines are based is that fluids when vaporized extract heat from sur rounding substances. The ammonia is kept in circulation in a system of pipes and, after being vaporized, is brought back in a fluid form and the heat ab sorbed by water.
Importance of refrigeration im portance of cold storage can scarcely be overestimated. Cold is the best method for preserving animal products. It pro duces no unfavorable change, either in the taste or nutritive value of the food thus preserved. On the contrary, the flavor and quality of meat is improved by refrigeration. Sarcolactic acid de velops in meat and brings about desir able ripening processes. Moreover, no hygienic objections can be raised against refrigeration properly done. It should be remembered that neither putrefactive nor pathogenic bacteria are destroyed by cold. They are, however, prevented from multiplying. When meat is placed in the cooler, there is a certain amount of excess moisture which must evaporate in order to allow the successful handling of the meat subsequently.
In light hogs, according to Wilder, this shrinkage in weight is 3 per cent within 4S hours, 41/2 per cent within 72 hours and about 5 per cent within 94 hours. Grassman states that in a care ful shrinkage test, beef had lost S.S per cent after four months in cold storage at a temperature of 25° F., pork 7.4 pet cent and mutton 11.5 per cent; after nine months, beef lost 17.8 per cent in weight, pork 12.8 per cent and mutton 23.4 per cent. In this test mutton froze most quickly and beef most slowly. Ac tual freezing has given satisfactory re sults also with fish, game, fowls, eggs and milk. Under ordinary refrigeration temperatures, without freezing, meat can be kept from decomposing only for a few weeks. Hengst found, for exam ple, that calf and hog quarters begin to show evidence of decomposition within two weeks and beef quarters after 24 days. Mutton kept well more than four weeks. Decomposition is due to bacteria and begins on the surface of the meat where it is at first confined. Underneath this surface layer the meat is still in good condition. The loss of weight in cold storage during the first few days is not greater than would occur in the open air.
Estimation of amount of ice, etc, the farm where ice is used for refrigera tion, 1 pound of ice under the best con ditions will cool down 3 pounds of meat from a temperature of 80° F. to the lowest point possible with melting ice. After that the amount of ice required to keep the meat cool will depend on the construction of the cooling room, insu lation and ventilation. In different packing houses which use artificial re frigeration, 1 square foot of pipe surface containing the refrigerating mixture is allowed for every 3 to cubic feet of space in the chilling room. Different estimates are required if Gardner's cur tain system of exposed brine circulation is used.
Cooling beef It has been found de sirable in packing houses to put beef into the coolers as soon as it is dressed. Coolers should have two separate com partments, in the first of which the tem perature should be 40 to 45° F., or at most, not above 50° F. The next day after killing, beef is placed in the main cooler, where a temperature of 34 to 36° F. is maintained. The use of a preliminary cooler with a moderate tem perature is not only economical but necessary for the proper preservation of the meat. Wilder has well described the troubles which arise when an at tempt is made to cool beef too quickly. The outside layer of meat is chilled, thus forming an insulation against the inside and causing so-called bone-sour or bone-stink beef.
Beef has the best appearance, however, if it is put into the preliminary cooler at once. For the first 24 hours beef should hang from 12 to 18 inches apart, according to the size of the animal; later it may be pushed closer together. Sep arate pieces of meat must not be placed in contact with one another in the cool ing room. This is a mistake which is often made on the farm, with the result that the meat does not keep well. The pieces must hang free or be separated by grating with air spaces between them. If all sanitary requirements are met cleanliness, dryness, ventilation, etc beef can be kept without decomposition for several months at a temperature of 33° F.
Cooling pork Formerly the operators of packing houses left hogs over night in an open air hanging room. During this time the carcasses cooled off some what and became dry. Better results are obtained if the hogs are at once put into the cooling room, in which the tem perature may run up to 45° F. during the process of filling, but should fall to 36° F. within the first 12 hours, and to 32° F. within 48 hours. Before the pork is cut the cooling room should be brought down to 28° F. With sheep there is no danger of cooling the car cass too fast as long as the temperature of the cooling room is above 32° F. The animal heat escapes rapidly from mutton for the reason that the carcass is thin. Mutton may be thoroughly chilled and dried ready for shipment within 24 hours.
Eggs in cold storage Refrigeration of eggs has grown to be a business of such proportions that more than $20, 000,000 worth of eggs are annually held in cold storage in this country. Re garding the practical details of cold storage for eggs, Cooper has collected some interesting information from men who are engaged in the business.