To determine the sterility of ketchup, cultures were made from 77 of
the bottles. The method used was to wipe the bottles and cork stoppers
with a damp towel and then remove the cork. The cork puller which
was used grasps the neck of the bottle in such a way as to cover the
opening and remove the cork without the inrush of air that occurs when
the ordinary corkscrew is used. A flame was then passed over the mouth
of the bottle, after which the upper layer of ketchup was poured out,
so as to discard any material which might have been contaminated in
handling. Tomato gelatin was used as a medium and cultures were made in
petri dishes.
There were 17 plates on which no organisms developed, indicating
that the ketchup was sterile. Of the 60 plates having organisms, 54
had molds, 22 of these having molds alone; 21 plates had yeast-like
organisms, 3 plates having these only; 29 plates had bacteria, 4 having
bacteria alone. Sometimes a plate would have only one form of organism,
but more often there was a mixture present. Of 15 plates having only
one form of organism, 3 had yeast alone, 2 bacteria alone, and 10 had
mold alone. Of the 77 bottles of ketchup from which the inoculations
were made, 41 were without and 36 with preservative, and of the 17
sterile ketchups, 8 contained sodium benzoate and 9 were without
preservative.
A considerable part of the experimental ketchup proved not to be
sterile. The organisms present were of the class which require oxygen
for their growth and therefore they had only been arrested in their
activity. No growth could take place so long as the air was excluded
and therefore no spoilage could occur. When the cork was drawn, the
organisms could grow and cause spoilage, and this is a much more
potent factor than the entrance of germs from without. Bottling and
sealing the ketchup quickly while hot so completely excludes the air
that only a few colonies of yeast or mold may be found on subsequent
microscopical examination. Filling at a low temperature and corking
while cool allows sufficient air to remain incorporated in the ketchup
and neck of the bottle to permit a considerable growth of the organisms
and a product derived from good stock may thus acquire the appearance
of ketchup derived from partially decayed material. A ketchup in which
bubbles of air are incorporated in filling may show a growth of mold
at each bubble throughout the mass. The foregoing statements apply to
ketchup containing sodium benzoate as well as to the non-preservative
goods of the character used in these experiments.