View report page

93
of the next sample, and it was emphasised that the samples
had been procured for chemical analysis and not for phosphatase
test. Had the sample been taken for the latter
purpose, particular care would have been taken to prevent
contamination with other milk.
I was unable to obtain any information with regard to
the third unsatisfactory sample.
In view of these findings I had a series of samples prepared.
One-third pint of pasteurised milk (which had
passed the test) was poured into a jug which had previously
contained raw milk, but which had not been drained or
cleansed, and a sample of this milk was submitted for
phosphatase test. A second sample was also taken from
one-third pint of pasteurised milk which had been poured
into a jug in a similar manner, but in this case the jug
had been inverted and drained for about five minutes. The
report on these samples stated in each case that the milk
was "raw or grossly underheated or contaminated with
raw or improperly pasteurised milk." The Lovibond blue
units value was 10+ as against a limit of 2.3 for properly
pasteurised milk. The same tests were made with one pint
of pasteurised milk poured into the same jug after it had
been used to contain raw milk. The sample from the jug
which had not been drained showed 3.7 units and from the
jug after it had been inverted and drained for five minutes
3.1.
The Analyst reported in both of these cases— "Some
error in technique of pasteurisation or contaminated with
a small quantity of raw or improperly pasteurised milk."
It will thus be seen that even the very thin film of milk
left on the inside of a jug after it has been drained for
some time when mixed with one pint of pasteurised milk can
be detected by this method. These tests, I think, confirm
the delicate nature of the test and show its value.