An experiment was made to determine the antiseptic value of vinegar and
acetic acid. Commercial 50-grain distilled vinegar was used. It was
found that when 30 per cent of this vinegar was added to the tomato
bouillon the development of mold was checked and the extent to which
it was checked increased with the increased amounts of vinegar. The
development in the solution containing 30 per cent of the vinegar
was two days later than the normal in starting, while the solution
containing 100 per cent was eleven days delayed and showed but little
growth.
An 80 per cent solution of glacial acetic acid was used. One-half of
1 per cent added to the tomato bouillon checked growth to the same
extent as 30 per cent of vinegar, and no development occurred when the
quantity was increased to 2 per cent.
Experiments were then made in which vinegar was added to the ketchup
in proportions varying from 1 part in 32 to 1 part in 8, with the
result of greatly delaying the appearance of the mold as the proportion
increased. With the increase in vinegar it was necessary to add sugar
and slightly more spices to overcome the pungency of the acid and thus
insure good flavor. The addition of the vinegar to the pulp had the
effect of arresting the action of the oxidase and thus the bright color
was maintained.
The usual custom in factory practice is to add the vinegar near the
close of the cooking process otherwise a considerable portion of the
acid will be driven off. This practice was followed in the experimental
work, but it has since been found that continued heating in the
presence of the acid has some effect upon sterilization, and therefore
the increased amount of vinegar is effective not only because of the
additional acid present, but also because the heating in the after
process is thereby rendered more efficacious.
This line of experiments gives promise of practical results in
producing a ketchup which will not only keep while in the bottle, but
will also keep longer after it is opened. Each manufacturer must work
out the quantities that could be used with his formula and still retain
the character of his goods.