If the pulp has been run through the sieving machine before cooking, the batch may be drawn off into the receiving tank for bottling. If the finishing be done after cooking, the pulp is run into a receiving vat, finished as quickly as possible, and drawn into the tank for bottling. The ketchup may be kept at a high temperature—200° to 206° F.—in the receiving tank by means of a small steam coil, or it may be drawn to the bottling machine through a steam-jacketed tube. Finishing after cooking yields a slightly smoother ketchup than sieving before cooking; but it necessitates handling, reduces the temperature, and increases the chances of infection.
BOTTLING.
The bottles should be thoroughly cleaned as ketchup will not keep if placed in bottles which have been merely rinsed to remove the straw; if the ketchup is not to be given an after process the containers should be sterilized. In the experimental work cork stoppers gave the best results and these should be sterilized in a paraffin bath at 250° F.
PROCESSING.
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.
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.