Scientists have often been accused of a desire to reduce the human diet to a pill or powder form “to be taken daily with water at meal times.” Whatever truth there might be in the allegation, it is an actual fact that more and more foods are being proved suitable for preservation in dried form. This is partially a logical development of the processes of food preservation, which are largely the concentration of food products for convenience in transport and storage, and partially the results of special war‐time demands. The need for concentrated nourishment is never greater than under conditions of war stress, and the present serious pressure upon Allied shipping facilities has further tended to increase the need for foods that occupy the least possible space. On the average, one pound of fully dehydrated food is the equivalent of fifteen pounds of the same product in its original form. Thirty dozen eggs in the shell, packed and created for shipment, occupy 2¼ cubic feet; dried, the same number take slightly more than one‐half cubic foot. The saving in ships and cargo space is obvious. While the problem of shipping space has been a major factor in the stimulated interest in dehydration, other elements in the existing situation have also had their influence. In Great Britain, under constant threat of invasion, it has been essential to build up reserve stocks of food throughout the country, often under storage conditions that are far from ideal. The serious shortage of tin has restricted the use of ordinary canning methods to foods which cannot, at the present stage of research, be preserved in any other form. A further stimulus has been given by the necessity of providing concentrated foods for paratroops and commando units, which must be entirely self‐sufficient when in action. Special rations are prepared which provide meals for two or three days, yet weigh only a few pounds. Drying is the oldest known form of food preservation, in fact it may be termed the natural method of preservation. Nature herself uses it. On the average, seeds, grains and nuts contain less than 10 per cent. of moisture, regardless of the amount which may be present at earlier stages of growth. The very existence of vegetable life from year to year is in the final analysis dependent upon this lack of moisture which inhibits the growth of bacteria and moulds. Perhaps by some accident, perhaps by imitation of the natural process, man early began to preserve food by drying, either in the sun or by artificial heat. Robinson Crusoe's raisins and the dried apples of our pioneer ancestors leap at once to the mind. Dried fruits and fish, jerked and smoked meats are all preserved by the removal of some part of their original water content. Sometimes this is the sole process, sometimes it is combined with other methods, as salting or pickling. In recent years, however, the preservation of foods by canning, refrigeration, and latterly by quick‐freezing has largely replaced the earlier method. Natural or artificial drying methods have in the past permitted the storage of food and the retention of a part of its nutritive value at the expense of flavour and colour. Everyone knows the difference between the flavour and texture of sweet corn in the milky stage and that which has ripened further, i.e., begun to dry out. In the case of such products we have largely come to prefer the dried flavour, even where we can know the so‐called fresh flavour. Some artificially dried or semi‐dried foods have, in fact, retained their place in the modern diet in direct competition with the fresh form, not as substitutes, but as independent food products in their own right. Such fruits as dates, figs, prunes and raisins are perhaps the best examples. No one expects raisins to take the place of grapes or prunes to have the same flavour as plums. These so‐called dried fruits are, however, really only semi‐hydrated. They retain from 20 to 25 per cent. of their moisture; only enough has been removed to ensure their keeping qualities. While they are a concentrated product, the process has not been carried to the point of complete transformation into the solid form. Jerked or dried meat and such products as pemmican are also among the oldest forms of preserved food, and jerked beef is still extensively produced in many countries. A more generally known form of meat product is meat extract. There are a number of famous brands, available either as a thick syrupy liquid or in a solid cube. The keeping property is implicit in its low water content, usually about 15 per cent. These extracts are prepared by removal of the fat and albumen, the addition of salt and evaporation in vacuum. One pound is ordinarily obtained from twenty‐five pounds of lean meat. Packing companies in the United States report that experimental methods of producing a true dehydrated meat, one which can be restored to its normal character, have been successful, at least in regard to beef. Pork is apparently too fat for such treatment. If the process works on a commercial scale as successfully as in the experiments, additional savings in shipping space will be realised. It is estimated that one ship could carry as much meat as ten cargo vessels were able to transport during the last war. Among other concentrated foods that go back to antiquity are the milk products, butter and cheese. These belong to the class which has little relation in either flavour or texture to the original from which they are made. Cheese is a product of fermentation as well as drying, while butter is additionally protected by salt and by refrigeration in storage and transport. Thus, while the removal of water is an important step in their manufacture, they cannot be considered dried foods. Recent reports from New Zealand indicate that butter is now entering this category. As a result of research which antedates the war, the New Zealand Dairy Research Institute has perfected a method of dehydrating butter. The British Government has contracted to purchase 20,000 tons during 1942 and 1943. A trial shipment of 400 tons was made last year and was well received. According to a report from the Canadian Trade Commissioner in New Zealand, the process was developed originally in order to reach markets not served by refrigerator ships. The dislocation of the shipping facilities between New Zealand and Great Britain has eliminated the usual means of sending butter. The new product, however, can be shipped as general cargo on any ship that may be available. The dried butterfat can be used directly by industrial food manufacturers and its conversion into table butter is simply adding a matter of water and salt. Not only will it serve a valuable war‐time purpose of providing Great Britain with needed fats, but it will also relieve the position of dairy farmers in New Zealand. After the war it is considered possible that the original purpose of marketing in countries without refrigerator service may continue to absorb available supplies.
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