Ketchup may be prepared either from the fresh tomatoes, or from pulp.
The most common practice is to prepare it from fresh tomatoes, although
some manufacturers prefer to make ketchup during the winter, when they
are not so busy with other products, and therefore use pulp. Presuming
that the same quality of stock is used and the same care used in
manufacture, there are some advantages in making ketchup from fresh
tomatoes. The pulp loses some of its color by bleaching, and a ketchup
made from pulp is naturally subjected to more heating than that made
from fresh tomatoes.
In the manufacture of ketchup the fresh tomatoes may be broken by
steam or by the use of a mechanical breaker. Both methods have their
advantages, some preferring the one method, some the other.
In securing good quality in ketchup the same factors must be considered
as in the making of pulp. These factors are care in manufacture and the
use of a raw product of good color and quality. For discussion of these
points in regard to pulp, see page 7.
The constituents used in the manufacture of ketchup in addition to
the tomatoes are sugar, vinegar, salt, onions and spices. The sugar
generally used is granulated cane or beet sugar. Some of the lower
grades of cane sugar may be used satisfactorily. The terms used to
designate grades of sugar below granulated do not always give a correct
idea of the purity of the sugar and in buying such grades it is best to
have samples submitted and have analyses made for sugar content.
The vinegar generally used is 100-grain distilled vinegar.
The salt used is of the grade known as dairy salt.
A variety of spices is used in the manufacture of ketchup. Among these
are cinnamon, cassia, cloves, all-spice, pepper, cayenne pepper,
ginger, mustard and paprika. Spices may be used either in the form
of whole spices, ground spices or volatile spice oils. Whole spices
are thought by some to produce a better flavor. Ground spices, when
used, should be secured from a reputable manufacturer, as there is a
possibility of adulteration or use of low-grade material in ground
products. Volatile spice oils are used to some extent, especially of
spices containing large amounts of tannin, where there is liability
of discoloration due to the formation of iron tannate during the
manufacture of the ketchup. Acetic acid extracts of spices are also
used to a limited extent.
The sugar may be added at any time during the making of the ketchup,
but is preferably added during the latter part of the cooking. There
is less danger of scorching if added at this time. It should be added
gradually and scattered over the surface of the cooking ketchup so that
it may go into solution more readily.
Vinegar is always added a few minutes before finishing. The acetic acid
of the vinegar is volatile, and a large portion of it will be driven
off with steam if added at the beginning of the cooking.
Salt may be added at any time during the cooking, but it is best to add
it sufficiently soon so that it will be dissolved and thoroughly mixed
with the product.
The onions should be added chopped at the beginning of the cook.
Spices, either whole or ground, are generally placed in a bag and added
at the beginning of the cook. If the volatile oils are used, they
should be added shortly before finishing the ketchup, as otherwise a
large amount of them may be carried off with the steam.