If it is a fraud to dye an unripe orange to make it look ripe, why should it be permissible to dye winter butter to make it look like summer butter?”, he says. Or one might add, to dye a biscuit brown to imply the presence of chocolate or to colour a cake yellow to simulate the addition of eggs? Our third heading is, What? What colouring matters should be allowed, and upon what conditions? Great Britain is the only leading country which has not a legal schedule of permitted colours. In this country any colouring agent may be added to food, except compounds of antimony, arsenic, cadmium, chromium, copper, mercury, lead and zinc. Gamboge, picric acid, victoria yellow, manchester yellow, aurantia and aurine are also prohibited. The addition, however, of any other colouring agent which is injurious to health would be an offence under the Food and Drugs Act. Other countries, including the United States of America, France, Canada, Australia, New Zealand, Italy, Spain, Sweden and Denmark have drawn up lists of permissible colours. And so the question arises—is it preferable to draw up a list of permissible colours or one of prohibited colours? It is obvious that if only certain colours are prohibited the remainder may be legally employed so long as they are not injurious to health. Thus a colouring agent may be used for a considerable time before it is proved to be injurious, whereas, if only‐certain colouring agents which have been previously proved to be non‐injurious were permitted, this risk of possible danger to health would be avoided. There is no doubt that in many cases proof of injury to the health of the human being is difficult to obtain. Much of the work that has been carried out to establish whether a particular dye is harmless or not has involved the use of dogs as test subjects. This does not appear to be a very satisfactory method of testing, for obviously dogs may react very differently from human beings towards chemicals. A dog's digestive powers are stronger than those of humans. No one would think of suggesting that bones are suitable food for humans just because dogs love them! Matta found that the capacity to depress the human digestion is possessed not only by poisonous dyes but also by dyes which he had proved to be non‐poisonous to animals. In bacteriology the addition of very small amounts of certain dyes to the culture medium will retard the growth of particular organisms and therefore it would seem possible that some dyes might adversely affect the action of enzymes in the body. So it would seem of importance that, if possible, all colouring matters, before being permitted to be used in food, should be proved by a competent authority to be harmless to human beings. If the effects of colouring matters upon the human digestive processes cannot be easily carried out in the body then it might be possible to perform such tests in vitro, using artificial gastric juice. It may be argued that the proportion of colouring matter added to food, ranging from about 1 part in 2,000 to about 1 part in 300,000, is so small that any particular colouring agent would need to be a deadly poison before any appreciable injurious effect upon health would occur. This argument does not, however, take into account the possible injurious effects which may be caused by the frequent ingestion of colouring matters which may have but mild toxic properties. It is known, for instance, that many synthetic colours have marked antiseptic properties even in highly diluted solutions, and therefore they may adversely affect the digestive processes. In any case, surely it would be wiser to eliminate all risks by requiring that official physiological tests should be carried out upon colouring matters before they are permitted to be used in food. One has to safeguard not only the healthy person but also the very young, the old and those who are of a delicate constitution. A harmless colour has been defined in Canada as one “which will not retard digestion nor have special physiological effects when consumed in quantities corresponding to 2 grains per day per adult.” The Departmental Committee in its report on “The use of preservatives and colouring matters in food,” published in 1924, stated that “It appears to us that definite evidence from direct experiments should be obtained as to the harmlessness of a dye before its use should be permitted in food. We have therefore come to the conclusion that a list of permitted colours should be prepared and that no colours other than those in such a list should be allowed to be used in the preparation of food. The list should, in our opinion, be prepared by the Minister of Health and issued by him, provision being made for the consideration of claims advanced by traders for the recognition and approval of additional colours on satisfactory evidence of harmlessness. We do not think that action such as this should seriously embarrass manufacturing interests, or is a course on which it is unreasonable, in view of the importance of the subject, to insist.” Yet, in spite of these recommendations of the Committee, no list of permitted colours was passed into law, and one wonders why. One argument against the drawing up of a list of prohibited colours is that even if a non‐prohibited colour is proved to the satisfaction of a given Court to be injurious to health that decision is not binding on other Courts and so there may be a lack of uniformity. A certain colour may be permitted in one town and prohibited in the next, which fact might add to the difficulties of the large scale manufacturer whose products are sold over a wide area. The leading manufacturers of dyes for use in food no doubt exercise great care in their preparation and such products are normally free from objectionable impurities, but it is possible that other dyestuff manufacturers are not so particular concerning the purity of their products. For instance, about 1938 a firm was fined for selling “Damson Blue” containing 540 parts of lead per million. Therefore it would seem necessary that some official control over the dyes that are sold for use in food should be introduced. The manufacture of some dyes involves complicated processes, and it is stated that in the production of one particular colour over 100 different chemicals are used and thirty different reactions, occupying several weeks, must be carried out before the finished colour is produced.
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