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practice has fallen into disuse, and they are now broken and
mixed in the ordinary way. The boiling is carried out in various
utensils over the open fire of a living room. The mixture stands
for cooling purposes in the living room, or in any out of the way
corner, sometimes in the open yard or area. The freezing takes
place early on the following morning in the " freezers."
A " freezer" consists of a tin or galvanised iron cylinder, or
container, in which the mixture is placed. The cylinder fits into
an outer vessel of wood or metal so loosely as to leave an inch or
two of space all round. In this space is placed broken ice and
salt, and the inner cylinder is rotated from time to time in this
ice medium. No ice is added directly or indirectly to the
mixture itself, nor are colouring agents used as a rule. The
utensils and materials appear, as a general rule, to be clean.
From this description, which applies, generally speaking, to
the ice-cream industry in Finsbury, it will be seen that the
" ice-cream," is boiled for some time, and in all probability
sterilized, and in due course it undergoes, at least approximate,
freezing. These facts, added to the generally wholesome
condition of the elementary materials used, would appear, at first
sight, to place the substance beyond risk of contamination. But
the critical period is the time of exposure between boiling and
freezing. Boiling sterilizes, but freezing does not sterilize.
Hence, if in the long cooling process the substance is exposed to
contaminated surroundings, the result may be, in effect, a
contaminated ice-cream. Such, in fact, frequently occurs.‡
Hence it would appear that it is not the process of manufacture
that we need to supervise so much as the general condition of
the houses in which the substance is made, and of the persons
who make it, and the manufacture so far as length of time
between boiling and freezing is concerned. The majority of the
° I am, of coarse, aware that genuine ice-cream is made by freezing a mixture
of cream (with a little milk), fruit, or fruit-pulp, and sugar. Other forms are
also made.
‡ See investigations by Klein, Cook, Wilkinson, Foulerton and others.