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In this connection, and in an effort to improve the standard, the
Ministry of Food, in April, 1949, advised local Authorities that additional
supplies of sugar and fats had been made available to manufacturers,
providing an undertaking was signed that their product would have a
minimum fat content of 2½%. The Memorandum added that this figure
must not be regarded as an interpretation of a proper standard. This
'gentleman's agreement' has worked satisfactorily so far as local
manufacturers are concerned.
The renewed manufacture of Ice Cream following the end of the
war, and the outbreak of typhoid fever at Aberystwyth in 1946 resulted
in the introduction of tests to define Ice Cream in four grades of
Bacterial cleanliness. These tests, still being applied, are, however, only
provisional, and their statutory value at National Act level anyway, may
be discounted. The indication is that no satisfactory test has yet been
devised for this purpose.
The Methylene Blue reduction test is the one adapted. It is noteasy
to describe in simple terms, but briefly, after very important preliminaries,
the Methylene Blue dye is added to the Ice Cream. Bacteria in the Ice
Cream extract oxygen for survival and increase, and this chemical change
causes the dye to lose its colour. Obviously, then, the number of
bacteria present will bear relation to the speed of reduction of the dye.

It is of course, important to remember that all organisms are not
disease producing, and it is very possible that a Grade 4 Ice Cream is
completely harmless from that angle. Such a grading, however, does
indicate that somewhere in the process either of manufacture, transport,
storage or even in the actual serving, some unhygienic factor is present,
and that factor could be dangerous.
The instructions, outlining the technique for examination of
samples, state:—"Samples may be kept at atmospheric (shade)
temperature for a period not exceeding two hours from the time of
sampling. If the sample cannot be delivered to the laboratory by the
end of that period, it should be well packed in ice in a carrying case, and
should always reach the laboratory within six hours from the
sampling The test should be set up at 5 p.m. on the day on which
the specimen is taken."
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