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Several samples of tomato puree containing mould have been tested for aflatoxin, with negative
results, but no information is available regarding tests for other mycotoxins.
As regards the general question of the probability of toxigenic moulds occurring in rotting
tomatoes it should be said at once that enquiries so far have elicited no specific grounds for
apprehension. The principal moulds encountered in over-ripe tomatoes,6,19 mainly introduced by
pest or air-borne infection are represented by species of Colletotrichum, Oospora, Mucor, Alternaria,
Rhizopus, Botrytis and Phytophthora, which do not appear yet to have been incriminated.
Nor have the fungal parasites to which the growing plant is subject20, and which are also liable
to occur to some extent in the fruit, so far come under suspicion; the commonest being Fusarium
oxysporum, Verticillium alboatrum and V. dahliae, which cause wilt; Pythium, Phytophthora,
Collectotrichum, Thielaviopsis and Rhizoctonia species, which cause root and foot rots; Botrytis
cineria and Didymella lycopersici, which cause stem rots, and Cladosporium fulvum, the common
leaf mildew. Sclerotinia sclerotiorum does not usually affect tomatoes but could arise from intercropping
plants; the fungus of "pink rot", it causes dermatitic lesions if handled and would
consequently be undesirable in food.
A potential danger might arise, however, from the use of fallen tomatoes; the ripe fruit providing
an ideal medium for many soil organisms, especially such genera as Aspergillus, Penicillium,
Fusarium, Cladosporium, to which many toxigenic species belong.
A Legal Standard ?
The question has been raised whether a maximum permissible Howard Mould Count for tomato
products in United Kingdom should be prescribed by Regulation.
In favour of such a standard it is argued that both the trade and the enforcing Authorities
would know exactly where they stood in this respect; that the standard would be enforceable not
only on retail sale but at Ports of entry throughout the country; this would eliminate the dodging
from Port to Port believed to have occurred in the past; the analyst's task would be simplified —
one official test for soundness, yea or nay, with perhaps a latitude of 5%; any injustice to the
supplier would be unlikely since a high count always indicates bad stock or improper handling although
a low count does not always indicate sound stock; and that limits for mould in tomato products
have already been adopted in other countries and proved workable.
Against a legal standard are some of the other points mentioned above, viz:—
(1) Factors affecting the Count. Variations in samples and in the aliquots examined; in the training
of the analyst; in factory methods, comminution, straining, etc.; and that the method lacks the
precision desirable in any procedure intended for the enforcement of Food Standards Orders and
Regulations.
(2) Factors affecting its significance. The lack of a reasonably constant relationship between
mould count and percentage of rot. The method takes no account of rot, disease or unwholesomeness
caused by other factors. Its foundations are based upon American data, not necessarily
applicable to European conditions where different fungal flora may predominate10. There would be
no latitude for exceptional climatic influences. The mould count, if too high, could be reduced in
the factory by finer straining and by addition of pulp from unripe tomatoes, with consequent reduction
in the quality of the product. In certain growing districts where climate favours rapid
fungal growth there might be a temptation either to pick the fruit before it was ripe or to apply excessive
treatment by fungicides. Finally, under present law a Public Analyst may base his opinion
as to the soundness of a sample of food upon any tests that may be desirable, and in the event of
a prosecution it is open to the defence to challenge his certificate or testimony on any relevant
grounds; if the legal test for soundness were based solely upon a Howard Mould Count the field of
cross examination open to the defence would be restricted to one figure, the significance of which
could not be questioned.
The above arguments will be sufficient to show that whilst the test is of undoubted value as
an indication of soundness, and suitable for incorporation in a trade specification or a Code of
Practice, any proposal to lay down a legal standard for the Howard Mould Count to Tomato Products
as a basis for criminal proceedings would require very careful consideration.
REFERENCES
1. Howard, B.J., Tomato Ketchup under the Microscope, U.S. Department of Agriculture, Bureau
of Chemistry, Circular No. 68, 1911.
2. Report of Proceedings at London Tomato Puree Conference, Food Trade Review. 1963, 33,
48-65.
3. Law Report, J. Assoc. Public Anal., 1964, 2, 46.
4. Law Report, Brit. Food J., 1967, 69, 153.
5. Stations Sperimentale per l'Industria della Conserve Alimentari, Parma, Italy, Food Trade
Review, 1963, 33, 57.
6. Mould Counting of Tomato Products, 1960, published by the Continental Can Co., Inc., of
100, East 42nd Street, New York, 17.
7. Howard, B.J., and Stephenson, C.H., Microscopical Studies on Tomato Products, U.S. Department
of Agriculture, Bull. No. 581, 1917.
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