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out. The test is considered to be satisfied by milk which gives a reading
of 2.3 Lovibond blue units or less.
The methylene blue test is a test based on the time taken by milk
to decolorise a dye, methylene blue. This test is deemed to be satisfied
by milk which fails to decolorise methylene blue in thirty minutes.
52 samples of pasteurised milk were submitted for examination,
all of which satisfied both the phosphatase and methylene blue tests.
Examination of heattreated milk — sterilised
Sterilised milk is required to satisfy the requirements of the
turbidity test. This test consists of mixing the sample of milk with a
reagent, and the mixture after filtration is required to be free from
turbidity in order to satisfy the requirements of this test.
Five samples of sterilised milk were examined during the course of
the year and all the samples were of the required standard.
Icecream — grading
Icecream is submitted to the Public Health Laboratory for
bacteriological examination. The icecream is graded according to the
time taken to decolorise a dye, methylene blue. The test is a provisional
one and because of the many factors which govern the hygienic quality
of icecream it is recommended officially that judgment should be
based on a series of samples and that too much attention should not
be paid to the result of an individual sample. It is suggested that over
a six monthly period, at least 50 percent of a vendor's samples should
fall into grade 1, 80 percent into grades 1 or 2, not more than 20 percent
into grade 3 and none into grade 4.
During the year 64 samples of icecream were submitted for bacteriological
examination with the following results :—

In general grades I and II are satisfactory, while grades III and IV
may indicate some defect in manufacture, handling or storage. Such
cases are followed up and advice is given.