While tomato ketchup is a complex and variable product, its general
composition may be determined with a fair degree of accuracy. Inspection
will give a good idea of color, consistency, smoothness of body,
fineness of finish, tendency to separate, presence of objectionable
particles, and evidence of gross fermentation. The odor and taste will
give a clue to the kind and quantity of spices used and to a certain
extent the character of the raw material. Judging by odor and taste is
not so well done as judging by the eye by most persons. The education of
those two senses has been neglected and therefore fail to give all the
information which might be acquired in this way.
A chemical examination which will give the specific gravity, total and
soluble solids, sugar, salt, and total and volatile acidity, will be
sufficient to give a good idea of the stock used—tomato, salt, sugar,
and vinegar, but not the spices. A microscopic examination will assist
in determining the condition of the material used and whether
decomposition has taken place before or after manufacture. The facts
obtained through these sources will permit of classifying commercial
ketchup with a fair degree of accuracy.
There has been a very marked change in the character of ketchup since
the transition from the preservative to non-preservative goods, not only
microscopically, but also in composition. Formerly, there were very many
brands of thin liquid ketchup, showing little concentration of pulp,
very low in sugar, and having only small quantities of vinegar; the
standard was bulk rather than quality. The microscopic examination also
showed that the product had frequently undergone change before and after
preparation. Recent examinations show that there has been a very marked
improvement; that the body is decidedly heavier, more sugar and vinegar
are used, the tissue is cleaner, and there are fewer organisms present,
also that the difference in composition in preservative and
non-preservative ketchup is small, whereas, formerly it was marked.
The variations found in ketchup of rather recent examination show in the
non-preservative kind the specific gravity varied between 1.091 and
1.177; the solids between 19 and 37 per cent; the salt between 2 and 4
per cent; sugar between 12 and 29 per cent; and volatile acids between
.54 and 1.24 per cent. In the preservative kind, the specific gravity
ranged from 1.032 to 1.120; the solids from 9.23 to 28 per cent; salt,
1.48 to 3.4 per cent; sugar, 4.95 to 16.9 per cent; and volatile
acidity, .16 to .64 per cent. As a class they averaged lower in
concentration of tomato and in sugar and vinegar, though if proper
sterilization had been used, some of them would have kept without
difficulty. In experimental work it was found that a ketchup
concentrated so that when finished it showed an added sugar content of
15 per cent or more, a total acidity of 1.2 per cent, and a specific
gravity of 1.120 or more, that it would keep. To obtain a total acidity
of 1.2 per cent means the addition of about .4 to .6 per cent acidity in
the vinegar used. However, there are brands of ketchup on the market
which keep well after being opened and which have a total acidity of
less than 1.0 per cent.
The manufacturer can use the following as a starting point for
non-preservative ketchup; pulp, 100 gallons; sugar, 60 pounds; salt, 8
pounds; vinegar, 100 grain, 2 gallons; spice to flavor; and concentrate
to 50 to 55 gallons.
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