London's Pulse: Medical Officer of Health reports 1848-1972

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Malden and Coombe 1956

[Report of the Medical Officer of Health for Malden & Coombe]

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19
The difference between a dealer's and a supplementary licence
is that, if a dairyman has premises in a local government area
where he retails milk he is issued with a dealer's licence. Should
he retail milk in another area he must obtain a supplementary
licence from the Council of that area.

DETAILS OF MILK TESTING.

CLASS OF MILKNumber of Samples TestedAppropriate TestsNumber of Samples
PassedFailed
Pasteurised89Phosphatase881
Methylene Blue89
Sterilised3Turbidity3
Tuberculin Tested (Pasteurised)44Phosphatase44
Methylene Blue44
Tuberculin Tested (Farm Bottled)1Methylene Blue1
Biological1

The purpose of the phosphatase and methylene blue tests is to
determine respectively whether or not the milk has been adequately
heat treated and whether it is of good keeping quality.
The turbidity test for sterilised milk is to determine whether
or not the milk has been adequately sterilised.
The greater importance must be attached to the phosphatase
test as correct heat treatment or pasteurisation reasonably ensures
that all pathogenic organisms have been eliminated.
This test is highly sensitive and a failure will result if
the milk has been heated to only 1½°F lower than the correct
temperature of 145°F (holder process), or held for twenty minutes
at 145°F instead of thirty minutes. The addition of as little as
a quart of raw milk in 100 gallons of pasteurised milk will
produce an adverse result. Failures may result from any one
of these three factors and inspection of the plant is necessary to
ascertain the cause.
Farm bottled (tuberculin tested) milk is not pasteurised and
is retailed without treatment.
It is pleasing to record that only one milk sample taken during
the year failed to pass an appropriate test.