An after treatment or process is given to bottled goods either in a
water or steam bath, the important point being that the center of the
bottle be raised to the desired degree of heat. If the ketchup is thin
this can be effected quickly, but if it is thick and heavy the heat
penetrates the ketchup with surprising slowness. In a thin ketchup
the temperature may be raised from 140° to 190° F. in eighteen minutes
or less when the surrounding heat is 195° F; but in a heavy ketchup it
may take an hour or more to accomplish the same result. It is therefore
very important that the ketchup be processed immediately after it is
corked, before it has time to cool. The rate at which the heating is
effected for different goods can be determined by sealing a thermometer
in the cork and recording the readings.
[Illustration: Fig. 4.--An example of factory practice showing the
top row of tanks from which pulp passes by gravity into the cookers,
then into the receiver, sieving machine, and final tub ready for the
bottling machine or jug filler.]