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42
result in the remaining milk showing a deficiency amounting to 20 per cent. of fat,
and (c) that milk served from a counter pan and not so stirred may show 32 per
cent. deficiency of fat after two hours and as much as 45 per cent. after
six hours.
2.—EXAMINATION OF MILK DISTRIBUTED BY CHURNS ON
"PRAMS."—A pram churn is a receiver holding about 15 gallons which is supported
on the framework attached to two, three or four wheels. The churn has a
tap at the bottom through which milk is drawn from the churn. The pram is
drawn through the City and milk is served as desired by customers.
Sixteen gallons of milk were received, placed in the churn, well plunged and
a sample taken from the upper level. This sample showed 3.10 per cent. of fat.
The milk was received at 10.30 a.m. and the first round commenced at 10.45. At
12.15 the first round was completed, and a sample was taken from the tap and
examined. The fat content of this sample was 3.08 per cent. Five gallons of milk, to
represent the amount of milk which would have then been sold, were drawn off from
the tap and the second round was commenced at 12.20. At 1.45 a third sample
was drawn off which showed only 2.16 per cent. of fat. Five gallons of this milk
were now drawn off and the remainder of the milk in the churn, that is
five to six gallons, were well plunged. A sample of this well stirred milk was
taken and was shown to contain 3.36 per cent. of fat. These analyses are
set out in the following table:—
Constituents.
Original
Milk.
Sample of Milk
drawn from tap after
1¼ hours' perambulation.
Sample of Milk
drawn from tap after
2½ hours' perambulation.
Sample of the final five to
six gallons left in the churn.
Fat 3.10 3.08 2.16 3.36
Solids not fat 8.96 8.92 9.04 8.90
Water 87.94 88.00 88.80 87.74
100.00 100.00 100.00 100.00
These results clearly show that after a time the fat content of milk distributed
from a churn on wheels tends markedly to rise to the top, and a sample of milk drawn
from the tap at the bottom and taken half way through the distribution period will
show much less fat than the milk remaining in the upper layers. It is only occasionally
that a stirrer is available and the dealer in such circumstances exposes
himself to the risk of a prosecution should an official sample be purchased.
3.—EXAMINATION OF MILK CONTAINED IN CHURNS AFTER A
LONG RAILWAY JOURNEY.—It is frequently the practice of distributors to
receive milk at the railway station after a long journey and to mix a portion from
one churn with a portion from another. Unless the distribution is preceded by
thorough stirring of the milk the constituent elements of the milk will show marked
variations. For this purpose the milk in a churn, selected at random, was examined,
the samples being drawn off by means of a syphon tube. The first sample
was drawn from the churn at a level of two inches from the bottom, the second at
a level of 12 inches from the bottom, and the third at a level of 5 inches from the
top of the milk. A fourth sample was taken after the milk in the churn had been
well plunged and mixed. The churn in question arrived from Darsham, which is
95½ miles from Liverpool Street, and contained 16 gallons of milk. In this experiment
it was found that No. 1 sample was 46 per cent. deficient in fat, No. 2 was
10 per cent. deficient in fat and the third showed marked excess of fat. The mixed
milk contained 3.22 per cent. of fat. The analyses are as follows:—
Constituents.
No. 1—taken 2" from the
bottom of Churn.
No. 2—taken 12" from the
bottom of Churn.
No. 3—taken 5" from the
top of the Churn.
Analysis of the Milk after
being well plunged.
Fat 1.60 2.68 9.00 3.22
Solids not fat 9.12 8.94 8.24 8.96
Water 89.28 88.38 82.76 87.82
100.00 100.00 100.00 100.00
It is interesting to compare these results with those obtained by Dr. Wilson
and Mr. Charles MacAra, reported in the Medical Officer, of April 28th, 1923.
Samples of pasteurised milk which had stood all night in churns and which had been