After the bottles are sealed, they should be given a process to insure
sterility, the time being about fifty minutes for half-pints and an hour
and fifteen minutes for pints—or sufficient time to insure 190 degrees
F. for twenty minutes at the center of the bottle.
This step is omitted by many manufacturers, dependence for sterilization
being placed upon washing the bottle and subsequent heating for about
twenty minutes. The heating is accomplished by conveying the bottles
through a chamber containing numerous steam pipes at high temperature
and discharging them at the bottling machine. It is assumed that
sterilization of the ketchup has taken place in process of manufacture,
and the heat within the bottle will care for any infection which may
possibly have taken place at a later time from the cap or cork. The
safety of this measure depends upon using a fairly acid ketchup or one
with a heavy body. It is a risky procedure for mild or thin ketchup. It
is a common occurrence to have the stock keep apparently while in the
bottle, but spoil shortly after opening. The spoilage after opening is
most often due to forms which have been present since manufacture and
only need the presence of air to start growth, and are not due to
infection from the air. A ketchup will inhibit the growth of organisms
which gain entrance from without, while those which are present but held
in abeyance through exclusion of air, will sometimes grow. The writer
has samples of ketchup put up in 1906 which apparently are sterile, but
which will show spoilage within a few days after opening, though done
under sterile conditions, and the spoilage be identical in kind with
that observed soon after manufacture. How long these organisms will
remain alive is not known. In canning, no foods are considered safe
without processing, and the same principle is a good one to follow with
ketchup.
Processing may be accomplished in open tanks, in retorts, in specially
constructed pasteurizers, such as used in the brewing industry, and in
hot chambers, the method is not material, though there may be
considerable difference in point of economy.