ADULTERATION - COLOURING MATTER A similar criticism applies to the continually extending use of colouring matter in food. Civilized man requires his food not only to be healthy and tasty, but also attractive in appearance.
This is difficult to ensure, for the various colour ing matters which are naturally present in meat and fish, in fruit, legumes and green vegetables are of a delicate and changeable nature and easily affected or destroyed by cooking. The manu facturer who used to put up "green" peas in pots or tins for sale produced the effect by the wilful addition of a substance known to be injurious to health, namely, sulphate of copper. The copper combines with the chlorophyll, forming copper phyllocyanate, which, by reason of its insolubility in the gastric juice, is com paratively innocuous. Preserved peas and beans have been for so many years "coppered" in this manner that it is difficult to induce the public to accept these vegetables when possessed of their natural colour only. The use of copper compounds as colouring matters was prohibited in England in 1925.
Milk is naturally almost white with a tint of cream colour. When adulterated with water this tint changes to a bluish one. To hide this tell-tale of a fraud a yellow colouring matter used to be added by London milkmen. Very gradually this prac tice, which had its origin in fraud, extended to all milk sold in London. The consumer, mis-educated into believing milk to be yellow, required it to be so. Large dairy companies endeavoured to wean the public of its error, without success. In England the ad dition of colouring matter to milk was prohibited in 1925. From milk the practice extended to butter; natural butter is sometimes yellowish, mostly a faint fawn, and sometimes almost white. In agricultural districts this is well known and taken as a matter of course. In big towns, where the connection of butter and the cow is not well known, the consumer requires butter to be of that colour which he imagines to be butter-colour. Anatto, turmeric, carrot-juice used formerly to be employed for colouring milk, butter and cheese, but of late certain aniline dyes, mostly quite as harmless physiologically as the vegetable dyes just mentioned, are largely being used. In England, the addition of picric acid, dinitrocresol, Martius or naphthol yellow, aurantia and aurine (rosolic acid) is prohibited.
The same aniline dyes are also employed in the manufacture of an imitation Demerara sugar from white beet-sugar crystals. Aniline dyes are very frequently used by jam makers; the natural colour of the fruit is apt to suffer in the boiling-pan, and unripe, discoloured or unsound fruit can be made brilliant and enticing by dye. The brilliant colours of cheap sugar confectionery are almost invariably produced by artificial tar colours. Most members of this class of colouring matters are quite harmless, especially in the small quantities that are required for colouring, but there are a few exceptions, picric acid, dinitro cresol, Martius yellow, Bismarck brown and one of the tropaeolins being distinctly poisonous.
On the whole, the employment of powerful aniline dyes is an advance as compared with the use of the vicious and often highly poisonous mineral colours which Hassall met with so frequently in the middle of the 19th century. Mineral colours, with very few exceptions, are no longer used in food. Oxide of iron or ochre is still very often found in potted meats, fish sauces and chocolates; dioxide of manganese is admixed with cheap chocolates. All lump sugar of commerce is dyed. Naturally it has a yellow tint. Ultra marine is added to it and counteracts the yellowness. In the same way our linen is naturally yellow and only made to look white by the use of the blue-bag.
The same idea underlies both practices, and indeed the use of all colouring matters in manufactured articles, namely, to make them look better than they would otherwise. Within bounds, this is a reasonable and laudable desire, but it also covers many sins—poor materials, bad workmanship, faulty manu facturing and often fraud. Like sugar, flour and rice are some times blued to make them look white. All vinegar, most beers, all stout, are artificially coloured with burnt sugar or caramel. The line dividing the legitimate and laudable from the fraudulent and punishable is so thin and difficult to draw that neither the law nor its officers have ventured to draw it, and yet it is a matter which urgently requires regulation at the hands of the State. Practices which, when new, admit of regulation are almost ineradicable when they have become old and possessed of "vested rights." Recognizing this, the departmental committee, like the royal com mission on arsenical poisons, recommended that "means be pro vided, either by the establishment of a separate court of reference, or by the imposition of more direct obligation on the Local Government Board, to exercise supervision over the use of pre servatives and colouring matters in foods and to prepare schedules of such as may be considered inimical to the public health." Metallic Impurities.—In close connection with this subject is the occasional occurrence of injurious metallic impurities in f ood materials. Tin chloride is used in the West Indies to produce the yellow colour of Demerara sugar. The old processes of sugar boiling left some of the brown syrup attached to the crystals, giving them both their colour and their delicious aroma; with the introduction of modern processes affording a much greater yield of highly refined sugar white sugar only was the result. The con sumer, accustomed to yellow sugar, had the colour artificially supplied by the action of the tin compound upon the sugar. Nowadays all Demerara sugar, with the exception of that portion that is dyed with aniline dye, has had its colour artificially given it and consequently contains strong traces of tin.
Soda-water, lemonade and other artificial aerated liquors are liable to tin or lead contamination, the former proceeding from the tin pipes and vessels, the latter from citric and tartaric acids and cream of tartar used as ingredients, these being crystallized by their manufacturers in leaden pans. Almost all "canned" goods contain more or less tin as a contamination from the tin plate. While animal foods do not attack the tin to any great ex tent, their acidity being small, almost all vegetable materials, especially fruits and tomatoes, powerfully corrode the tin covering of the plate, dissolving it and becoming impregnated with tin compounds. These tin compounds are by no means innocuous; yet poisoning from tinned vegetable foods is of rare occurrence. On the whole, tin-plate is a very unsuitable material for the storage and preservation of acid goods. Certain enamels, used for glazing earthenware or for coating metal cooking pots, contain lead, which they yield to the food prepared in them. Food ma terials that have been in contact with galvanized vessels some times are contaminated with zinc. Zinc is also not infrequently present in wines.
