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106
The sale as pasteurised milk of raw milk, inadequately
heated milk, or pasteurised milk that has been contaminated
with raw milk, has lately been receiving attention in various
parts of the country and in the Metropolis. Complaints
regarding the quality of the milk supplied to school-children
under the "Milk in Schools" scheme; a recent outbreak
of typhoid fever in the country which seems to have been
traced to an infected milk supply; and many other considerations
which are too lengthy to deal with here, all
render the inspection both of pasteurising plant and the
milk supply a matter of urgent necessity.
This Borough was one of the first to initiate measures
designed to deal with this matter, and during the past year
inspections of plant and the testing of the milk for efficiency
of pasteurisation have been carried out. Until recently
inspection of plant was the only method of ensuring a good
product, but we have now a chemical test by means of
which we can judge the quality of pasteurised milk; this
is known as the phosphatase test, and depends upon the
fact that under the conditions obtaining in pasteurisation
properly carried out an enzyme naturally occurring in milk,
called phosphatase, is destroyed. In carrying out the test,
traces of phosphatase are sought for by delicate chemical
means and as a result one is enabled to express an opinion
as to the efficiency or otherwise of the pasteurising process.
Recently the test has undergone an extensive survey at
the hands of its originators and of other investigators,
which resulted in an interesting paper being published in
the Journal of the Society of Public Analysts, to which
Journal your Analyst also contributed a short note dealing
with the same subject. In these, all the conditions of the
test have been subjected to a searching enquiry, and it has
been shown that in skilled hands the test is capable of
detecting 0.3 per cent., or even less, of raw milk in
pasteurised milk and to give practically infallible indications
of inadequate heating.