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Research has been undertaken at Wantage Research Laboratory in co-operation with the
Central Public Health Laboratory, Colindale, and the City Corporation. Evidence has been
obtained that this process can be used effectively for this purpose. A dose of about 0.65 megarad
will completely eliminate salmonella. In fact the meat in practice will receive 0.5 to 0.7
megarad allowing for the distribution of the dose throughout the blocks of meat. This dose has
little effect on the quality of the meat. As long ago as 1962 some tons of meat were treated and
distributed and no adverse reaction was obtained from the trade. Some simple tests with Alsation
guard dogs demonstrated that no differentiation was made by the animals between treated and
untreated meat. The kind of bacteriological research done included studies in which different
serotypes of salmonella have been inoculated in large numbers into the meat and then irradiated
at different doses, when the meat was in the frozen state. The number of organisms surviving
were measured. The reduction in population in salmonellae achieved by the recommended dose
is by a factor of about 10'. This means that if the salmonellae were 1 organism per gram
originally, then the reduction would be one organism surviving in 1 million grams.
The evidence is that the actual numbers of salmonellae involved in contaminated meat are
probably less than one organism per gram, so that the recommended dose would give a high
margin of safety with respect to survival and would certainly produce meat with a salmonella
content well below currently accepted methods of detection. This laboratory work has been
supported by the irradiation of samples of horse and kangaroo meat collected directly from the
Port of London from shipments highly suspect of being heavily contaminated with salmonella.
Control material has been demonstrated to be positive while in no instance has the irradiated
meat been found to be positive. These tests have involved several hundreds of samples.
The use of ionizing radiation has been suggested as an alternative to heat treatment, so
we must give attention to this method to see if it is possible. It has been suggested that
irradiation could be applied to all tne imported horsemeat, thus avoiding the necessity for
inspection and the other disadvantages already outlined. Of course it could be so applied if it is
an economic proposition and the trade accept the treatment as applied to all the meat apart from
inspection by us. The trade would see the advantage offered by the fact that the meat remains in
its present raw state and no doubt would support the idea. Another advantage would be that, with
the treatment of all the meat at a centrally located plant, control could be more easily exercised
by the Port Health Authority, thus avoiding the possibility that the meat could get into wrong
hands.
This method of treatment must also be considered from the point of view of legislative
control.
The Meat (Staining and Sterilization) Regulations define that meat which is found to be unfit
for human consumption must be sterilized (see above). Thorough cooking is the treatment normally
employed by the trade. If this new process is to be introduced then an amendment must be made
to the alternative methods of treatment, but we must be satisfied that the irradiation process
produces an effect equivalent to the heat process. The irradiation process has been designed
specifically to eliminate salmonellae, with the bonus that it also kills some of the other microorganisms
and that parasites are rendered innocuous. The dose required will deal effectively
with the vegetative organisms, but will not have such a great effect on bacterial spores or viruses.
How effective is the boiling process in regard to the elimination of micro-organisms? The
regulations state that the meat must be "sterilized", but certain bacterial spores are known to
survive the boiling process. In hospital practice a much more stringent standard of heat processing
is demanded before things are described as "sterilized*. As this radiation process is
described as being suitable to eliminate salmonellae and parasites, should we not allow it to
be applied to meat or other commodities where the presence of salmonella and parasites is the
reason for the meat being unfit? If we do allow it, we shall still be faced with the requirement
to inspect the meat in regard to other reasons for unfitness, and the usual macroscopic examination
for quality, chemical or other contamination, and other causes of unfitness could be carried
out before or after irradiation.
Would the application of this specific process leave us in the situation where we could
allow the importation of frozen horsemeat and its distribution in the raw state after irradiation,
being satisfied that the problem of cross-contamination from this meat of other foods with
salmonellae is solved. This imported horsemeat is claimed by the trade to be earmarked as
"pet meat", but some may find its way into the human food market. The boiling process does
change the nature and substance of the meat, making it unsuitable for the human market, whereas
the irradiation process leaves the meat in its original raw state. The question arises, therefore,
whether distribution of irradiated meat could be controlled.
Labelling of the packages is open to criticism in that the meat could be removed and the
discs tampered with. The ideal would be to have a test which could be applied readily to the
meat itself. Certain techniques are being tried by scientists interested in this method, and no
doubt this is one of the important questions which will be asked when the process is scrutinized
by the Ministry of Health Advisory Committee. The new Food (Control of Irradiation) Regulations,
1967, which came into operation on 1st June, 1967, regulate the use of irradiation in such a way
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