Experiments on the Spoilage of Tomato Ketchup

by A. W. Bitting

Oil extracts of the spices were tested in the same manner as the water infusions and the acetic-acid extracts. The oils were so strong that in order to handle them easily they were mixed with equal volumes of alcohol, except that the mace, which was in the form of a paste, was mixed with two-thirds its volume of alcohol. To 10 cc of tomato bouillon were added 0.1, 0.2, 0.3, 0.4, and 0.5 cc, respectively, of the oils of cinnamon, cloves, mace, mustard, and black pepper.

In the case of the mold, there was no development in the solutions containing cinnamon, cloves, and mustard; in those containing mace and black pepper the development was slower than the normal, that in the black pepper being more pronounced. On the yeast the effect was similar, no development occurring in the cinnamon, cloves, and mustard, and a retarded development taking place in the mace and black pepper, that in the black pepper being the more pronounced.

The experiments show that some of the spices, notably allspice, cinnamon, and cloves have decided antiseptic value, but that the peppers are not as valuable as is generally supposed.

The oil extracts have been advocated for use in ketchup instead of the whole spices, but in quantities which would be useful antiseptically their use would be objectionable, for when present in approximately the same proportions as are the whole-spice infusions, the flavor is too strong and masks the more delicate flavor of the tomato. The acetic-acid extracts are more effective than are the water infusions, and they are not objectionable in the ketchup.

VINEGAR AND ACETIC ACID.

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.