In these times—aptly described as the age of dehydration—few food products appear to have aroused as much technical interest as has dried egg. Upon this point we have the criterion of the galaxy of papers and communications in the various trade and scientific journals. Admittedly, much of the interest is doubtless due to the painfully rare appearance of the goods in the form delivered by the hen. However, there is little doubt that some of the developments in our knowledge and usage of a convenient form of an otherwise highly perishable commodity may have wide repercussions in food‐preparation in the future, both in industry and in the household. It would appear that the attaining and maintaining of hygienic conditions in the dehydrating plants has received the attention it warrants. Naturally, unless reasonable care in the storage or usage of the finished product is exercised, conditions will occur under which rapid contamination with and multiplication of bacteria will occur. The intention of the Dried Egg (Control of Use) Order, 1945 (S.R. & O. No. 627), which forbids the use of dried egg in certain foods and in materials sold in the wet state, is to provide against such conditions. Of the desirable properties which a dehydrated product should possess, ease of reconstitution is one of the most important. In the bakery and allied trades the difficulty, or, more correctly, the variability, of solubility of various deliveries of dried egg has occasioned some complaint. It is interesting to note that, with a view to assisting wetting, and hence reconstitution, addition of surface‐active agents, either to the egg pulp before dehydration, or to the dried product, has been the subject of several patents. As regards keeping properties, dried egg offers no exception to the general rule that the rate of deterioration on storage decreases progressively with reduction in the moisture content. It is reported that a product containing as little as 2 per cent. of moisture is being manufactured in U.S.A. Apparently, the only satisfactory packing for such a highly‐dehydrated product is a sealed metal container. The deterioration of dried egg powder, with the production of the peculiar and characteristic off‐flavour, has been shown to be connected with a small amount of glucose originally present. This decreases during storage, and the development of unpalatability may be correlated with the amount of glucose remaining. At the same time, the solubility of the powder decreases, rendering reconstitution more difficult, and the whipping or beating properties, so vital in the making of cakes, become impaired. Initial removal of the glucose, such as De‐controlled fermentation, markedly improves the stability of the product; re‐addition of glucose to an egg pulp from which the natural carbohydrate has been removed yields on dehydration a powder showing the same effects of deterioration as ordinary dried egg. Addition of reducing monosaecharoses other than glucose has a similar effect. Recently‐published reports of work carried out at the Cambridge Low Temperature Research Station provide strong evidence that the reaction mechanism resulting in the loss in solubility of dried egg powder is a two‐stage process. In the first stage, which does not in itself result in a decrease in solubility, the reducing group of the glucose molecule condenses with the free amino groups of the protein components; a further reaction then occurs which causes the protein to become insoluble. It had been previously discovered that addition to the egg pulp before drying of a simple amino‐acid such as glycine or alanine retarded the loss of solubility, although other forms of deterioration, such as the darkening of the colour of the powder, were not inhibited. Presumably, the glucose reacts preferentially with the added amino‐acid, instead of attacking the egg‐proteins. Another method of overcoming the loss of solubility is by the addition of substantial amounts of sucrose (or lactose) to the egg pulp before drying. How the protective action operates does not appear to be known, and it is peculiar that lactose, itself a reducing sugar, does not cause loss in solubility in the same manner as glucose. The “sugar‐dried egg” obtained on dehydration is readily soluble, and, since it possesses all, or nearly all, of the aerating properties of fresh egg, is claimed to be as good as frozen egg, or even shell egg, for cake‐making. Allocations of sugar‐dried egg are now being made to the bakery trade, and, should no difficulty be encountered in large‐scale production, it is to be presumed that in due course its use will become much more general. In the form now being supplied, sugar‐dried egg has an egg solids to sugar ratio of 2 to 1, thus allowing existing trade recipes to be rebalanced without recourse to awkward calculations. When reconstituted, 3 pounds of liquid egg contain approximately 5 ounces of sugar; this high sugar content of course restricts the use of this product to food preparations of a sweet nature. The mixture aerates rapidly, and, since it possesses a good oven spring, underbeating rather than full development of the batter gives the most satisfactory result. Additionally, the use of sugar‐dried egg lowers the amount of baking powder required; in some mixes baking powder may be omitted altogether. Sponges and similar goods of superior texture, flavour and keeping qualities may thus be made. Obviously, developments in other forms of dried egg and allied products are to be expected. Thus the previously‐mentioned protective action of lactose suggests the preparation of dehydrated mixtures of egg and milk or milk products, and in fact interesting experiments have been carried out involving the use of whey powder as a protective agent.
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