Home-made ketchup generally has a rather dark reddish or brownish color,
due to prolonged heating, made necessary under kitchen conditions. At
one time this was thought desirable and some of the older recipes call
for the use of caramel in order to imitate this color. Most
manufacturers now aim to secure a clean, clear color, preferably bright
red. This may be obtained when good fruit is used and handled quickly; a
muddy brownish or yellowish color is looked upon with suspicion as
indicating poor material or defective methods.
The necessity for a clear red variety has already been pointed out, for
without proper stock, a superior product of uniform quality can not be
made. The tomatoes must be well vine-ripened, as the presence of green
fruit and green butts has a decidedly dulling effect. Colorimeter tests
show that the use of even small quantities of green material have an
immediate dulling effect. Promptness in handling the fruit after the
tissue is once exposed to the air is also essential. The tomato, like
some other fruits, turns brownish when the surface is cut or exposed.
This does not occur as rapidly, nor is it so marked as in apples or in
pears, but it is present. When the tomato is converted into pulp, every
particle is exposed to the air for a very short time—long enough to make
some slight change. The change is most marked in pulp from raw stock and
least in that which has been well heated. It naturally follows that
ketchup made promptly from whole stock will have the best color, that
from canned tomatoes next, then canned pulp, and lastly, that from
trimming stock. Pulp allowed to stand hot for too long a time will have
a brownish color like stack burning. When barrel pulp was used, this was
ascribed to the tannin extracted from the oak.
Pulp should not come in contact with iron at any stage, as the union of
the acid of the fruit with the metal will cause discoloration. When such
discoloration does occur, it becomes uniform throughout the mass, and
not in the neck of the bottle as has sometimes been described.
Darkening in the neck of the bottle is frequently due to the spices
used, as has already been pointed out. It can be redistributed
throughout the whole by placing the bottle in a shaker for a short time.
Darkening at the top may sometimes be due to extraction of color from
the corks. Soaking corks in two per cent acetic acid, then in hot water
before drying, and paraffining, will assist in preventing discoloration
on cheap grades.
Discoloration in the neck also results from the small amount of air
incorporated and from any subsequent addition which may come in through
the cork or seal. Bottles which are full to the cork may show no
darkening, those having a space of an inch or more between the contents
and cork may show little discoloration, while those having more space
will show much more marked discoloration. This holds for both pulp and
ketchup and in this case the discoloration begins on the surface and
works downward. The product made from some fruit will discolor more than
that made from fruit grown in another section of the country.
A bright red color is secured in some brands of ketchup by means of
paprika, as indicated under spicing.
A light colored ring in the bottom of a bottle is generally due to
organisms and debris, indicative of the use of barrel or trimming-stock
pulp, or it may result from changes after the process of manufacture. It
has been mistaken for sand.