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Thus all the shellfish layings on the Essex shore of the Thames which are within the Port Health
Authority's area are controlled except a strip at the seaward (Eastern) end about If miles wide.
Shellfish from the "Prescribed Area" must not be sold for human consumption unless they
have been treated by one of the following methods:—
(1) Subjected to a satisfactory process of cleansing at an establishment which is for the
time being approved by the Minister of Health for the purpose, or
(2) Relaid in pure water for such period and in such places as may from time to time be
approved by the said Council for the purpose.
(3) Subjected to a process of sterilisation by steam under pressure for at least six minutes
in an apparatus which is for the time being approved by the said Council.
By far the most important shellfish in the area are Cockles. They are treated under Section (3)
above at establishments approved by the Port Health Authority for the purpose. There are at present
nine of these approved establishments at Leigh and one at Southend, and it has been the practice
for many years past to treat all cockles landed in the district by the same method, including those
cockles derived from areas which are not "Prescribed"
During 1950 /1951 a careful investigation was carried out into the methods by which cockles
were cooked and with the co-operation of the Industry, certain modifications were advised in the
apparatus.
The two main modifications advised were—
(1) The introduction of a reducing valve between the boiler and the cooking pots so that
steam could be introduced into the cooking pots at a steady and pre-arranged pressure.
(2) The extension of the "Three Pot System" of cooking (already in use by the more
advanced operators). This system of cooking makes it more certain that the operator will maintain
the six minutes cooking period required by the Regulations.
A report on the experiments in cooking cockles was included in the Annual Report for 1950.
Samples of cockles taken direct from the cooking pots have been subjected to bacteriological
examination over the past four years. The results have been most satisfactory, the vast majority
of the samples being returned as sterile.
The cooking apparatus in use does not comply with the strict letter of the Regulations since
there is no possibility of building up a steam pressure within the cooking pots. It does, however,
function most satisfactorily. It produces not only a safe cockle from the Public Health point of view,
but also a firm and uniform one which takes the salt well and which is acceptable to the trade.
A full account of the cockle industry and particularly of the processing of the cockles in the
cockle sheds and their distribution to the trade was given in the Annual Reports on the work of the
Port Health Authority for 1949, 1950 and 1951.
Ever since the outbreak of gastro intestinal disturbance which took place in the hot summer of
1949 among visitors to Southend and district which was clearly attributable to the consumption of
cockles, there has been a very close supervision of the cockle sheds at Leigh-on-Sea, which fall within
the jurisdiction of the Port Health Authority, and the retail local cockle industry which comes under
the jurisdiction of Dr. Logan, Medical Officer of Health of Southend and thirdly with the Director of
the Public Health Laboratories at Southend who carries out the periodic bacteriological examination
of samples of cockles taken at various stages from their treatment in the sheds to their exposure for
sale to the public.
The table facing this page presents in diagrammatic form the results of the bacteriological
examination of samples taken throughout the year of fresh unbrined cockles intended for immediate
consumption and reveals certain interesting and important features.
The table shows a direct correlation between the growth of organisms in the cockles and the
temperature of the water in the mains at Southend used for cleansing the cockles after the steam
cooking. It will be seen that excessive growth of organisms and incidentally of the poisons they
develop, begin to appear when the mains water approaches 58° P. and continues to be unsatisfactory
until the water returns to approximately the same temperature, i.e., cockles became, in 1953,
potentially dangerous on this account in mid- June and continued so right through the summer
months to the end of September and, in certain cases, until the end of October.
Can the growth of organisms be avoided ? First by the observance of scrupulous cleanliness
throughout the whole process from the sterilisation of the cockles in the steam retorts (a large number
of samples tested reveals that the cockle meat is in fact sterile on emerging from the retort) right
through to the time when they leave the cockle shed for distribution to the retail trade.
Secondly by keeping the temperature of the water in which cockles are washed (it will be remembered
that the cockles pass through four washings before they are completely free from sand, shell
particles and other extraneous matter) as low as possible, in order to check the growth of bacteria.
This is by no means easy to achieve and would involve an expensive refrigerating apparatus through
which the mains water would have to pass before being used in the washing tanks.
A third method—a heavy brining of the cockles, would prohibit the growth of organisms but
would completely disturb the trade in fresh cockles since the brine would have to be washed out
before they could be eaten and in any case the flavour of the fresh as against the heavily brined
cockle would to some extent be lost.
Both these precautions—scrupulous cleanliness at the cockle shed and the use of water at a
temperature less than, say, 55° F., will only be achieved as an economic proposition in the trade
when the proposal of the Southend Corporation to erect Municipal cockle sheds becomes a reality.
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