To determine the keeping properties of the ketchup on the market,
various brands were obtained from the grocery stores. In the
majority of cases nothing was known of the ingredients or methods of
manufacture, except what appeared on the labels. No date of manufacture
was given, and in some cases the dealers did not know the age of the
product.
There were 104 bottles of ketchup opened to find out how long they
would remain in good condition. These were kept in the laboratory,
though the temperature was higher than that at which ketchup should be
held. Of the 104 bottles there were 66 without preservative, according
to the labels, 46 of which spoiled. Of the 20 which did not spoil, 2
formed crystals of benzoic acid on the covers of glass dishes during
evaporation. Of the 39 which, according to the labels, contained sodium
benzoate, 15 spoiled. The bottles of unspoiled ketchup after remaining
in the laboratory for about a month were placed in the incubator at
95° F. for three weeks, and were then taken out, and have been left in
the laboratory since. The metal cap had been taken off frequently for
observation, and the ketchup exposed, but the treatment did not cause
them to spoil.
The average number of days after which spoilage occurred for the 46
bottles without preservative was about fifteen, the minimum number
being four days, the maximum number ninety-four days. The average
number of days preceding spoilage in the case of 15 bottles with
preservative was twenty-four days, the minimum number being three and
the maximum sixty days. The majority of these had 0.1 per cent of
sodium benzoate present; the others had a smaller amount, according
to the manufacturer’s label. These data are not at all conclusive and
further work on material of known history will be necessary.