FROM time immemoria the freshness or otherwise of an egg has been a perplexing problem to the housewife. Even at the present time it is probable that the majority of people do not know how to tell whether an egg is good enough until they have broken it. This is strange inasmuch as the method of finding out the condition of eggs is so simple that anyone can folIow it; moreover, the test given is one which is relied upon by the trade and may therefore be taken with confidence. All that is necessary in order to carry out the experiment is a dark room in which a candle has been placed. Now take the egg and hold i up between the eye and the light. A new-laid or very fresh egg will show clearly an air space in the larger end between the sheIl and the lining membrane. If the egg is really new laid this should Ibe very smaIl, for it tends to increase as an egg is kept. All the rest of the surface shown should present a homogeneous and translucent appearance; if the article is positively bad, a number of dark spots wiII be visible. A glance at the accompanying photographs wiII readily give an idea of the two qualities. Once the test has been performed there is no reason why anyone should ever be taken in over the egg question. There is little doubt that milk, especially in towns, is stiII subject to the time-worn practice of adulteration with water. If skiIIfully done this is not very easy to detect if the mere appearance of the liquid is considered. There is one very simple test which will tell us at once whether the milk is of a good quality and rich with a proper amount of cream. Take a sample of the milk and place it aside in a receptacle; a smaII tube is good for the purpose. Stir the milk well and then take a thick bright knitting needle. Plunge this to a depth of several inches in to the milk and hold it stead- ily slanting downward. If the milk is of a rich quality the fluid will slowly gather in a drop at the end of the needle and this wi1l remain, for rather a long time. On the other hand, supposing water has been added the drop will hardly form at all, and even if it should it will not stay but will quickly fall. Poorly fed cows on occasion .will live grounds. Happily it is not a difficult matter to distinguish between margarine and all other butter substitutes, and the pure article. The so-called “spoon” test has been commonly employed by analytical ch\lmists for a long while, and is very r\liable. A sample of butter two or three times the size of a pea is placed in a large spoon and heated over an alcohol burner, or if this is not available an ordinary lamp or gas burner will do as well. Good fresh butter will boil V\lry quietly, producing a number of small foamy 'ubbles. On the other hand, margarine and most examples of made-up butter will crackle and splutter, making a noise very similar to that which is caused by the placing of a green stick on a hot fire. Still another point of distinction is to be noted if a portion of the sample be placed in a bottle and this is placed in water warm enough to melt the butter. If this is kept warm for half an hour the fat wiII either be cloudy or entirely clear. In the former case the material is certainly margarine or at any rate not pure butter; in the latter instance however, the article may be adjudged to be of a high standard of purity and freshness. Some of the cleverly made process-butters which are on the market do not always give very definite results but a little study of the matter wiII enable the experimenter to judge the extent of the adulteration of which he is the victim. Of the commonly used breakfast beverages there is little doubt that coffee is the most widely adulterated. Fortunately, again, there are some simple tests by means of which anyone may determine the character of the article which he buys. When the admixture of foreign matter is carelessly done an examination of the grains with a powerful magnifying g],ass wiII be sufficient. Absolutely pure coffee should give an entirely uniform appearance, but the presence of adulterants which may take the form of ground peas, beans or a host of other articles is readily observed. Chi cor y , which of course may have been open ly employed is recognized by its dark and gummy grain; this is very.
This article was originally published with the title "Simple Tests for Food Purity" in Scientific American 105, 20, 432 (November 1911)