British Food Journal Volume 42 Issue 8 1940
Article publication date: 1 August 1940
At a meeting of the Nutrition Panel of the Food Group of the Society of Chemical Industry, Dr. Joseph Needham, of the Biochemical Laboratory, University of Cambridge, speaking on “ The Biological Nature of the Egg,” pointed out what complex structures were the eggs of birds and other vertebrates. In fact the embryo, which is eventually to develop into the new animal, only occupies a very small space within the total egg. The remainder serves, in one way or another, to keep the organism alive until it is hatched. It is interesting to note that this is not the case in lower animals. The octopus in its egg is not supplied by its mother with enough copper but must obtain more for itself from the surrounding sea. Newts and frogs in their eggs also must to some extent look after themselves. Birds' eggs, however, represent a type of perfectly “closed box” structure which requires many ingenious devices in order to survive. One of these, through which the bird saves itself from being poisoned by its own by‐products, is the fact that the developing embryo does not excrete nitrogen as urea but in the form of uric acid which is more easily deposited as crystals.—Dr. Ethel M. Cruickshank, of the Department of Agriculture, Cambridge, who spoke on the “ Chemical Composition of the Egg,” pointed out that the hen was a physiological machine for turning raw materials into human foodstuffs. The amount of such human food which the hen could produce in a day depended on a number of factors, but to a large extent it was true to say that the bigger the hen the larger the egg. The number of eggs which a hen would lay in a year was a different matter, but an interesting point was the fact that high production had little or no detrimental effect on the quality of the eggs. In considering the composition of the egg one must divide it into three parts. The shell was principally made up of calcium carbonate, although small amounts of magnesium, phosphorus and organic matter were present. The white was composed of four different kinds of protein and could be divided into layers of thick and thin white. The proportion of thick to thin white influenced the culinary value of the egg. Together, the four proteins in the white contained the essential amino acids which made “ first class ” protein. Egg white contained minerals and also supplied valuable amounts of vitamin B. The yolk contained two proteins which were also shown to be of “ first class ” quality. Besides protein the yolk contained 30 to 32 per cent. of fat. Numerous minerals were present, including relatively rich amounts of easily assimilable iron. Vitamins A, D, B1 and B2 were also present. The anti‐rachitic vitamin D was of great significance in the diet. Dr. Cruickshank also discussed the factors in the diet of the hen which might give the yolk an unpleasant taste or a strange colour. Although the amount of fat, and hence the total food value of the egg, could only be influenced to a slight extent by the diet of the hen, the nature and flavour of the egg could be very strikingly altered by feeding mashes containing, for example, hemp seed or linseed oil. As regards vitamins, it was essential that plenty of these should be present in the diet of the hen in order that her egg might be of high nutritive value. As regards minerals, it was very well known that by feeding a hen a diet which was short of calcium a thin shell was obtained. However, the calcium content of the yolk and white were not affected. The amount of iodine in eggs was affected by the amount in the hens' food, although iron and copper appeared to be independent of the amount present in the diet.—Dr. S. K. Kon, of the National Institute for Research in Dairying, Reading, spoke on the nutritive importance of eggs in the diet. He stressed that eggs share with milk the ability to cover nutritive requirements during the period of rapid development. The vitamins, minerals and “ first class ” protein in eggs made them one of the protective foods. In particular, eggs supplemented very well the proteins present in cereals. Dr. Kon showed in detail how eggs contribute to the various factors of a good diet.—Dr. R. B. Haines, of the Low Temperature Research Station, Cambridge, spoke on the preservation of eggs. He showed how hens' eggs were in a state of rapid change. The aim of storage was to retard or stop this change and prevent the attack of outside agencies such as micro‐organisms. Although storage only affected the nutritive value of eggs to a very minor degree, any loss of palatability and cooking quality was a clear indication that certain slight chemical changes had taken place. Dr. Haines mentioned three methods for the large‐scale storage of eggs. The first was cold storage, the second, storage with the partial addition of CO2, and the third, full gas storage. For other purposes, drying or freezing could be used. Problems connected with the storage of eggs led to the consideration of questions of production and handling. For example, “ thick white ” was apparently due to the individual hen. Again, spoilage of eggs by the invasion of bacteria was influenced by the structure of the egg‐shell, which might vary greatly in successive eggs from the same hen or by the “ washing ” treatment which the eggs received. Among many other topics upon which Dr. Haines touched were “ swollen ” and “ flabby ” yolks due to loss of moisture, “ watery whites,” “ sunken ” and “ sided ” yolks due to chemical changes, and eggs with “ whiskers,” due to the growth of fungus on the shell.—Miss Mary Andross, of the West of Scotland College of Domestic Science, Glasgow, gave the final paper on the subject of “ The Cooking of Eggs.” Research in domestic science concerned itself with what effect such factors as temperature, time, rate of cooking, acidity, or the addition of salts, might have on the nutritive properties of eggs which were boiled, poached, fried, scrambled or made into omelets, custards, mayonaise, meringues, angel cakes, or sponge cakes. Another important factor which was the subject of scientific investigation was the effect of the age of the egg in relation to its cooking qualities. Miss Andross also discussed the waste of food value which might take place in different methods of cooking, and she concluded by discussing the effects which different treatments might have on the digestibility of the food.
(1940), "British Food Journal Volume 42 Issue 8 1940", British Food Journal, Vol. 42 No. 8, pp. 71-80. https://doi.org/10.1108/eb011344
MCB UP Ltd
Copyright © 1940, MCB UP Limited