The pulp is evaporated rapidly to such consistency as the grade and
price will warrant, the reduction in volume being from 40 to 60 per
cent. This is accomplished in about forty-five minutes. The cooking is
not continued longer than is necessary, as each minute added to the
cooking darkens the finished product.
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.