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75
The freezing point determination gives a more accurate basis of calculation
as its range of variation from the average is considerably less than the range
of variation from the average in the case of solids-not-fat. In the latter
case the range of variation from a basis figure of 8.5 per cent. is greatly to
the benefit of the milkman who is tampering with the milk.
Sample L 105 in the table shows that the milk probably contained 8.83
per cent. of solids-not-fat which had been reduced by the addition of 2.8
per cent. of water to 8.58 per cent. The sample, however, satisfies the
requirements of the regulations. This milk was supplied under contract
to a hospital in November when milk is normally of good quality.
Similarly samples E 11 and M 97 reported as poor quality samples contain
more truly about 5 per cent. of added water.
In the case of sample C 65 the adulteration was confirmed by the freezing
point method. The "third part" as previously stated was sent to the
Government Chemist who returned 5 per cent. of added water.
The freezing point determination can only be carried out on fresh milk.
This method therefore could not be adopted alone as an official method under
the present regulations as the "third part" is usually several weeks old
before it is sent to the Government Chemist.
Reconstituted
Milk.
One sample (B 122, informal) admitted by the vendor to consist of
reconstituted milk, had been made from dried skimmed milk. The sample
contained 0.85 per cent. of fat and 20.62 per cent. of solids-not-fat. The
vendor stated that it was used in the manufacture of soft cheese.
Two samples of milk D 30 and D 31 obtained in the ordinary course of
sampling were found to contain excessively high percentages of solids-not-fat;
both these samples had been supplied to the retailers by the vendor of the
reconstituted milk mentioned above. It was also reported from a neighbouring
borough that milk containing excessively high solids-not-fat was
being supplied by the same wholesaler who had had some difficulty in obtaining
supplies owing to a scarcity of milk at this period. In appearance all three
samples could not be distinguished from natural milk. The samples were
apparently made from skimmed dried milk by admixture with water and
cream and final pasteurisation. Skimmed dried milk and a churn of cream
were in the yard when the sample of admitted reconstituted milk was obtained
by the inspector.
During the past ten years 8,600 samples of milk have been analysed;
the annual average percentage of solids-not-fat has ranged from 8.65 to 8.79
and no single sample has had a composition approaching the figures obtained
in samples D 30 and D 31.