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GROUNDNUTS AND COLOURING MATTERS
The following articles on Groundnuts and Colouring Matters are submitted by the Public
Analyst, Dr. H. Amphlett Williams.
Groundnuts
In 1960 outbreaks of an apparently new disease occurred in young turkeys causing over
100,000 deaths. The disease, which became known as "Turkey-X" disease, although later found
to affect other domestic birds, particularly ducks, was traced to a large consignment of Brazilian
groundnut meal that had become affected by a fungus, Aspergillus flavus. Investigation showed
that this fungus, quite a common one, produces a highly toxic metabolite, to which the name
"Aflatoxin" has been given, and that even minute proportions of aflatoxin, of the order of one or
two parts per million of the groundnuts, causes an acute hepatosis characterised by necrosis of
the liver parenchyma and proliferation of the bile duct epithelium. According to recent reports
aflatoxin has produced hepatomas in trout at a level of 0.001 part per million. This illustrates
the futility of attempting to apply quantitative limits for carcinogens. The toxin affects calves
and pigs, the young being particularly susceptible, and also causes liver carcinoma in rats, but
no scientific evidence is yet available as to its effect on man.
Consignments of groundnuts entering the Port are now being sampled and using a sensitive
method of fluorescent chromatographic analysis developed by the Tropical Products Institute,
aflatoxin has been detected in proportions ranging from "Low" to "High" in 7 out of 88 samples
examined since July 1964.
Colouring Matters
As a result of the recent development of entirely new analytical techniques artificial dyes
can now be extracted from complex and naturally coloured foods, isolated and often identified.
Many of the dyes formerly used in food have been found in animal experiments to be injurious, and
the coal-tar dyes now permitted to be used in food are restricted to a list of thirty, although eighteen
of these are of dubious or unknown safety. Since there are hundreds of dyes, however, the
identification of an unknown one, even after isolation, may involve very many tests, all on a
micro scale.
Although there is evidence that some dyes, particularly the oil-soluble ones, may produce
catharsis, the principal danger fromdyestuffs is associated with cancer, and accumulated evidence
indicates that a number of the azo, triphenylmethane and stilbenedyes are potent tumour-producing
agents.
This laboratory has been particularly exercised by the identification of dyes of the azo class
in various foods. Many dyes of this class contain in their molecule a naphthyl group attached by
the azo linkage to various supporting aromatic groups. They include some of the finest dyes,
fast, and apparently quite safe on materials in everyday use, and even in cosmetics or when painted
on the skin. But when swallowed they become subjected to the digestive processes of the body,
and recent biochemical studies indicate that the molecule is first split at the azo linkage into
smaller molecules, the naphthyl moiety being reduced to naphthylamine and then hydroxylated; the
hydroxyl group becoming attached, when other positions around the nucleus are occupied by substituent
groups, to the ortho position (i.e. next to the amine group). The ortho hydroxy naphthylamine
thus formed is believed to be the actual carcinogenic agent and this compound has been
shown to induce cancers of the liver, bladder or other parts of the excretory system. In a similar
manner dyes containing other aromatic amine groups capable of being converted by reduction and
hydroxylation to the respective orthohydroxyamines are also suspected to be carcinogenic.
The well-known Sudan Red dyes are of the orthohydroxynaphthylazo class and have been
found in this laboratory in several imported foods. In 1959, 26 samples of Brazilian oranges were
found to be coloured with Oil Orange XO (Sudan II). The consignments were stopped and no further
samples coloured with this dye have been detected.
In 1964, seven samples, and in 1965, twenty-one samples of imported spices — Chilli, Turmeric
and Curry Powders, mainly from East Africa — were found to contain prohibited dyes, viz:
Sudan Red G, Brilliant Croceine, Sudan HI and Sudan IV, the last three being disazo dyes, capable
of reduction to two potentially carcinogenic breakdown products. These dyes had been added not
only to improve the appearance of the spice but in many instances to conceal admixture with pea
flour and husks, rice and other cereals; a form of adulteration apparently common a century ago
when red lead was used as the colouring matter.
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