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139
produce a pure product although his utensils were sterilised. He was
persuaded to boil the mix; and further samples proved to be very satisfactory.
A sample of ice cream powder proved to be sterile.
One vendor received Ice Cream from a firm in another part of London.
The ice cream was supplied in a container packed in a box filled with dry
ice. The Box and Container were placed on the pavement outside the shop.
In addition the spoons used for serving the ice cream were of doubtful
cleanliness and the shop-keeper generally had no idea of the importance of
cleanliness and the dangers of allowing the ice cream to become infected
B. Coli were found in 01 c.c. of a sample taken with the spoons normally
used. The ice cream was manufactured in a small electric plant—a Fern's
emulsifier and pasteuriser— and samples taken at the source by the Medical
Officer of Health of the Borough concerned proved to be quite satisfactory.
Contamination in this case probably took place during or after delivery.
Many examinations were made of ice cream manufactured on a fairly
large scale in a local factory, with modern apparatus. Most of the samples
shewed a high bacterial count and B. Coli were present:—
Sample No. 1. 365,000 bacteria per c.c. B. Coli in 001 c.c.
2. 280,000 „ „ „ 001 c.c.
3. 48,000 „ „ „ 001 c.c.
4. 11,000 „ „ „ 01 c.c.
5. 18,000 „ „ „ 01 c.c.
The proprietor appeared to be conscientious. The ingredients used were
of good quality and the mix was pasteurised. Some of the samples were
taken immediately after production, so the possibility of contamination at a
later stage was eliminated.
Samples No. 4 and No. 5 were of ice cream made after special precautions
had been taken to ensure a clean product. Despite this B. Coli
were present. After many consultations with the owner it was suggested
to him that his pasteurising plant was not efficient. He alleged that the mix
was kept at 150° F. for 30 minutes. The plant was again inspected, and it
was found that the recording thermometer was fixed outside the vat near
the drawing-off tap in a situation where the true internal temperature could
not be recorded with any accuracy. This was confirmed by plunging a
second thermometer into the vat. This registered 130° F. when the outside
thermometer shewed 150°. The necessary adjustments were made, and a
further sample of ice cream shewed:—
Total bacteria per c.c. No B. Coli present in any
80 dilution.
It is apparent that strict supervision of ice cream manufacture is necessary,
and the extra work placed on a Public Health Department by so doing
is amply repaid by results. In addition, all persons whose premises are
registered for the manufacture or sale of ice cream should be given printed