British Food Journal Volume 45 Issue 5 1943

Abstract

It is only fair to say that this work is backed by a larger basis of research than exists in most countries. For nearly twenty years, that is since the formation of the “Dehydration Committee” by the Department of Agriculture in 1923, experiments have been carried on to determine the best methods of dehydrating Canadian apples, and the experience gained is now being applied to the dehydration of vegetables. One point which has been emphasised consistently throughout the work of the Committee is that high quality and fine flavour are essential for fruit or vegetables to be processed. During the past winter the Canadian Government was informed that the British Government was interested in dehydrated vegetables to an amount of approximately 1,000 tons. While the Canadian industry was not equipped to handle on short notice such a large order, immediate steps were taken in the establishment of test plants and the speeding up of experimentation. At that time representatives from the United Kingdom pointed out that no commercial samples of dehydrated vegetables from any country had been considered entirely satisfactory from the point of view of nutrition. The Canadian tests indicate that dehydrated vegetables can be of fine flavour and retain from 50 to 75 per cent. of the original vitamin content. Five experimental dehydration plants have been operating for some months, processing potatoes, carrots, turnips and cabbages from the 1941 crop. These are being held as a reserve supply for the Canadian Army. On the basis of these results, Canada should be able to supply large quantities of high‐quality dehydrated vegetables. The actual methods of dehydration employed vary according to the product. The simplest is that applied to the drying of fruits. Many of these, such as dates, figs, raisins, are dried in the whole state; others, apricots for example, are halved and pitted, while apples should be peeled, cored and sliced. Cut fruits, such as apricots and apples, are treated with sulphur dioxide, which acts as a steriliser and prevents discolourisation. Such fruits must be cooked before using in order to drive off the sulphur, but other dried fruits can be used without soaking or cooking. The moisture is removed by natural drying in the sun or by artificial evaporation. Many of the dehydration processes lie in the realm of chemical technology, but a short sketch of the principles involved may be of interest. The dehydration process used in the case of vegetables involves careful cleaning and cutting into small pieces, shreds or flakes. These are then “blanched” in steam or boiling water and placed in the dryer. While the amount of moisture which should be left varies with the particular vegetable, it should never exceed 7 per cent., and best results indicate a moisture content of 3 to 5 per cent. Substantial progress has already been made in research into the pre‐treatment of the vegetables. Cabbages, for example, should be “blanched” in steam, potatoes in plain water, and carrots in salt water. Investigation is continuing, however, into the actual drying of the vegetables and particularly as to the proper stage of maturity at which dehydration should take place. So far, it appears that no vegetables which are woody or fibrous have produced satisfactory results. Soft fruits, such as raspberries or strawberries, are reduced to a pulp, after the preliminary cleaning and “blanching.” This pulp is forced out over a heated drum, and when drying is completed looks something like “coloured crepe paper.” This filmy layer is broken into small fragments for packing and storage. It is reported that the original flavour and colour of the fruit is well maintained. The handling of milk and eggs, which are very liquid in their original form, requires a different process. After testing and preliminary sterilisation, the liquid is sprayed into a drying chamber where hot air in constant motion reduces it to a powder which falls to the floor. Although dehydrated foods can be kept under conditions of ordinary storage, they do require special care in packing. Metal containers are unnecessary, but the cartons must be impervious to moisture, to changes in temperature and to the attacks of insects and rodents. Canadian experience also indicates that removal of the oxygen in the container and its replacement by an inert gas, such as hydrogen, prevents any recurrence of chemical change and retains flavour for a considerably longer period. The acceptance of any product in war‐time, even for civilian consumption is, of course, no proof of its continued acceptance under normal conditions. Shortages of supply and the exigencies of the situation necessitate strange substitutions. Sometimes these are found better than the original product, and in the post‐war period tend to replace it. But this only occurs when the new substance or material has intrinsic advantages and can compete on a basis of quality. Many of us can remember the reaction in Great Britain against Canadian bacon after the last war, resulting from war‐time shipments of a type and quality to which the British were not accustomed. Long years of effort were necessary to break down the prejudice against Canadian bacon which was built up at that time. In the present war Canadian bacon is being prepared to suit the British palate. Since dehydrated foods have not yet come into general war‐time use it is impossible to prophesy regarding post‐war markets, but there are a number of interesting sidelights on the situation. One of the industries hardest hit by the tin shortage has been the manufacture of dog food, which had been growing rapidly in the pre‐war years. These manufacturers have been the first to produce dehydrated products to be sold to the general public, truly a case of “trying it out on the dog.” While we do not attempt to draw any analogy between dog biscuits and food for human consumption, it will be interesting to watch the results of this experiment. Dogs are certainly not interested in eating things that are good for them regardless of flavour, and if our canine friends accept the new preparations it will at least indicate that a palatable product has been obtained. The palatability of food can only be determined in use. It is feared, for example, that dehydrated vegetables would tend to become monotonous in constant use. General consumer interest has, however, been aroused by the wide publicity which has been given the industry, and already commercial dehydrators in the United States are studying the possibilities of civilian markets. The future of this development would appear to depend upon the assurance of quality, as the convenience of such products is undeniable.

Citation

(1943), "British Food Journal Volume 45 Issue 5 1943", British Food Journal, Vol. 45 No. 5, pp. 41-50. https://doi.org/10.1108/eb011377