FOOD PRESERVATION

New Zealand Herald, Volume LXXII, Issue 22259, 6 November 1935, Page 7

FOOD PRESERVATION

STORY OF REFRIGERATION THE HOUSEHOLD FRIEND BT OtTR FOOD SPECIALIST From the beginning man has faced the problem of keeping fresh and wholesome the food so necessary for his existence. Thousands of years ago he learned that heat directly or indirectly was responsible for the rapid decay of foods. By storing such foods in caves, or placing them in vessels in running streams or by the use of water-soaked cloths, similar to the <k evaporation system," he retarded the process of decay to some extont, while in the desert countries, where the atmosphere is extremely dry, ho learned to cure meats by exposing them to the wind and sun, a process known as " dehydrating " and still used for preserving fruits and meat products. Heat is not the only factor for the rapid development of destructive bacteria. Moisture is a very important factor, as without moisture bacteria growth ceases. In-the refrigerator, circulation carries the evaporated moisture, with its bacteria contents, away from the food. Original Ice Box The first ice box, or ice chest, on the market was simply a box with double wall's between which there was a layer of insulating material. The food placed in it was cooled as follows: —

The ice was placed in the upper part of the box. The air in contact with it was cooled and therefore contracted and became heavier, volume for volume, than the remainder of the air in the ice box. This cold, heavy air sank down through an opening in the bottom of the ico chamber and forced the warmer, lighter air up along the sides of the box. The warm air came in contact with the ice, was cooled, contracted, became heavier and sank. The cold air in its downward passage came in co'ntact with the food and absorbed heat from it. This explains how the food was cooled. Influence of Insulation

The temperature to Tvhich the air and food in that type of refrigerator are cooled by the ice depends upon the non-conducting or insulating power of the walls and upon the temperature of the outside air. The temperature of melting ice is 32deg. Fahrenheit. If the walls of the refrigerator were perfect insulators the ice would absorb heat and melt until the temperature of the air in the refrigerator was reduced to 32deg. Then the ice would stop melting and the air would remain at 32deg. That is, if the walls were perfect insulators the ice would last forever and tho air would remain forever at 32deg. There is, however, no such thing as a perfect insulator. Therefore, when the outside air is above 32deg. heat passes into the refrigerator through the walls, and it is difficult to maintain temperatures below 50deg., necessary to preserve foods, unless replenished with ice frequently. At, temperatures above SOdeg. bacteria _ multiply rapidly and decay will set in. Hence, over a period of years, extensive research work has been done on refrigeration, and so the preserving of the good points from the ancestors of the refrigerator and the discarding of the bad points has brought us the super-automatic refrigerator, which is now a matured servant to replace th& old-fashioned icebox. Essential Functions

A properly constructed refrigerator will lead the circulating air over the cooling chamber. The exceedingly cold freezer in the cooling chamber freezes the moisture • and its bacteria content out of the circulating air and attaches it to the cooling unit as a frost. At every revolution of the .circulating air past the the air is washed of its moisture ana bacteria. Proper and complete circulation, therefore, is even more important than low temperature. Low temperature stops the action of bacteria or spoilage. Circulation takes care of the slight but constant spoilage that low temperature does not stop, accomplishing a dry clean air around the foods that prevents odours, keeps tho food in a clean state of preservation and thus produces real refrigeration. Refrigerators that make this possible must be true, circulating refrigerators constructed scientifically, with proper air leads. In purchasing one of these up-to-date pieces of equipment, firstly consider the proper construction. The best types keep the ice separate from the food, and subdivide the food compartment so that foods such as eggs, milk and butter, more sensitive to odours, may be kept by themselves. The interior construction of the box may be of wood, galvanised iron, enamel, or porcelain, but whatever it is, it should be smooth, free from cracks, made of material impervious to moisture and odours, and easily cleaned. For general efficiency the racks should bo made of tubes or wire, so smooth as will be easily cleaned, so close together that there is little chance for tipping and spilling of dishes. The ideal arrangement for spacing between shelves is a movable one, so that one may ha\'e the maximum amount qf storage space. The hardware of the refrigerator, especially the door latches, should be of the best non-rust quality, but more important is the tightness with which the doors fit. They should be so tight that not even a thin piece of paper can be slipped inside tho doors when the doors are fastened. Tho metallined ones are more easily cared fdr, as the metal naturally resists moisture and odours. Other important facts to be considered aro tho cost of operating, tho amount of noise created in operating, and tho ease with which it may be installed and repaired.

CHERRY CAKE To make a cherry cake, M.H. has sent the following recipe in answer to an inquiry from E.B.: —Line a caketin with greased paper. Mix together carefully l2oz. flour and one teaspoon baking powder.' Grate into this the rind of one lemon. Cream togother 80•/,. butter and 6oz. brown sugar. Add to butter and sugar throe well-beaten eggs, stir in the flour lighty and carefully, and add 4oz. crystallised cherries cut in halves. If needed, add a little milk, but keep mixture stiff. Put in the papered tin and bake in a moderate oven about one and a-half hours. Wholemeal used in place of the flour gives a fuller flavour. To make sponge drops break four eggs into a basin and separate yolks from whites. Beat the yolks well and mix with them 6oz. fine sugar and the grated rind of one leirron, and beat together for quarter of an hour. Then sift in gradually 6oz. flour and, having whisked the whites to a stiff froth, stir them in. Beat mixture well another five minutes, then sot littlo blobs or "fingers" of it out on some sheets of stiff clean white paper. Put in a hot oven at once and bake about five minutes, but watch thorn carefully as a few seconds too long will scorch and spoil thom. When very lightly coloured they are done. Remove from paper by damping its underside and fill them at once if used with filling, or put in a closed tin or jar to keep till needed.