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The Adulteration of Food.

From "The Romance of Modern Chemistry".
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Many common foods contain foreign materials introduced with the direct object of defrauding the public and securing a larger profit to the seller. Even the ordinary food-stuffs of the breakfast-table are not always what they seem, with the exception, perhaps, of sugar, on the purity of which one can depend. The reader may be interested to hear a little about the ways in which these foods are adulterated, and about the methods by which the fraud can be detected.

In the case of milk the chief, and one might almost say the natural, adulterant is water. New milk contains as much as 87 per cent, of water, and the uninitiated might suppose that it would be very easy to add a little more without detection. Careful analysis, however, will always reveal any such manipulation, although it must be borne in mind that there may be a certain difference in the richness of milk from various cows.

One method which the chemist has at his disposal is the determination of the specific gravity - that is, he finds out how much heavier the milk is than an equal bulk of water. It is worth while remembering that the first recorded determination of the specific gravity of a substance was in connection with a question of fraud. Hiero, the King of Syracuse, had commissioned a goldsmith to make him a crown out of a certain quantity of gold. When the smith brought the finished crown, Hiero somehow suspected that there was an admixture of base metal, and asked Archimedes to find out for him whether this was so. The philosopher took a lump of pure gold equal in weight to the crown, and put each into a vessel full of water. He found that more water overflowed from the vessel into which the crown had been put than from the other, and concluded rightly that the crown must contain some lighter and baser metal. So the determination of specific gravity as a means of detecting fraud is a time-honoured practice.

If a bulk of water were taken which weighed exactly 100 ounces, an equal bulk of pure new milk would weigh about 103 ounces, a little less or a little more, according to its source. That is, the average specific gravity of milk may be taken as 1.03. If, then, a certain sample of milk had a specific gravity of only 1.02, we might be sure that it had been "watered." On the other hand, the fact that the specific gravity of a sample is 1.03, does not prove the milk to be satisfactory; for, curiously enough, it is possible, by a judicious combination of watering and skimming, to get a product which has the same specific gravity as the original milk.

The reader, of course, knows that the fat contained in the milk - in other words, the cream - rises slowly to the surface; but he may not have drawn the conclusion that this fat must therefore be lighter than the milk. What is left after removing the cream-that is, the skimmed milk - is actually heavier, bulk for bulk, than the fresh milk; its specific gravity is higher than 1.03. By adding water to this skimmed milk in the proper proportion, the specific gravity is brought down to the normal figure of 1.03, and this "milk" is indistinguishable from fresh milk unless further tests are applied.

It will probably be suggested that a mere glance at this "milk" would show that it had been skimmed and watered. But our adulterator is not so easily caught; he perpetrates fraud upon fraud, exhibiting an ingenuity which is worthy of a better cause. A judicious admixture of a yellow dye to skimmed and watered milk is found to produce a rich, creamy appearance, and the public is delighted with its milk supply. So is the adulterator; he has sold his "milk" at the standard price, and he has still the cream to dispose of.

Since, then, the appearance of the milk and even the determination of its specific gravity may fail to give any proof of adulteration, further examination is necessary. The analyst must proceed to find also what is the amount of fat present in the milk. This is very quickly ascertained by treating a measured quantity in a centrifugal machine; the fat or cream under these circumstances separates almost immediately, and its bulk may be determined. If the amount of fat is less than 3 per cent., the milk has certainly been tampered with, since the normal product never contains a smaller percentage of fat than this. A thorough examination would include also the determination of the non-fatty solids, consisting chiefly of casein and milk-sugar; but a description of this would take us rather far.

Butter is another household article that is readily and frequently adulterated, although the recent Butter and Margarine Act should do something to protect the public. The usual frauds practised in the case of butter are (1) the sale of "renovated" or "process" butter as fresh butter, and (2) the substitution of a certain amount of cheap beef fat or lard for the true butter fat. Renovated butter is obtained from rancid butter by a process in which the objectionable matter is removed; the product is rendered sweet for the time being, and is sold as choice butter.

Artificial butter, on the other hand, or margarine, as it is commonly called, is prepared from beef fat or lard, which is worked up with ordinary butter and colouring matter so as to resemble the real article. Besides a certain difference in the taste of butter and margarine, there is one very simple method, known as the spoon test, by which they may be distinguished. If a little genuine butter is melted in a large spoon over a small Bunsen flame, and the heating is continued, the butter ultimately boils quietly and foams up to the edge of the spoon. Margarine, treated in the same way, splutters about and crackles, but does not foam. The practice of selling margarine under the name of pure butter is probably dying out, but it is not so very long ago since a bold individual was prosecuted for actually advertising a process for the "scientific" blending of butter with beef fat or lard. Science, it would seem, covers a multitude of sins.

A food-stuff which is very frequently adulterated is chocolate. This substance is obtained by grinding cocoa nibs, which are the crushed kernels of cocoa beans. The nibs consist to about 45 per cent, of a fat, the so-called cocoa butter, and in this respect are quite different from the shells of the cocoa bean, which contain only 2 to 3 per cent, of the fat. Seeing that the price of cocoa nibs is about ten times that of cocoa shells, the common practice of adulterating chocolate with powdered cocoa shells is distinctly profitable. This fraud is best detected by the aid of the microscope, an instrument which is part of the necessary equipment of an analytical chemist's laboratory. To the practised eye the presence of the powdered shells is at once obvious.

There is another adulterant of chocolate or cocoa which is easily detected with the aid of the microscope, and that is starch. This substance is very widely distributed in the plant world, and occurs in all sorts of vegetables and cereals. The samples of starch obtained from these various sources, such as wheat, rice, potatoes, and maize, are chemically identical, but when they are examined under the microscope, the granules of which they consist are found to be surprisingly different in size and shape. The granules of wheat starch are circular, those of potato starch are oval, while those of rice starch are many-sided; the granules from maize starch, as found, for example, in corn-flour, are also many-sided, but are uniformly much larger than rice-starch granules. It is therefore possible for a skilled analyst to determine with the microscope whether any starch, and, if so, what kind of starch, has been used in adulterating a given food-stuff. He can also discover at once whether a certain kind of starch is pure or is contaminated with another kind. Obviously there is a temptation for the adulterator to add a cheap starch to a more expensive one, say potato starch to arrowroot, keeping the price the same. The microscope, however, soon exposes such a fraud.

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