A great deal of stress has also been placed upon the effect of the spices in acting as preservatives. Experiments have demonstrated conclusively that when these are used in the small quantities required for flavoring, that their effect is practically nil. The active principles of the spices are effective only when present in the proportion of 1 to 500 or 600 and in ketchup the proportion is only 1 to several thousand. Likewise the quantity of salt is too small to have effect.
The keeping qualities of a mild ketchup will depend far more upon the sterilization than most manufacturers realize. It is easy to make almost any ketchup apparently keep while the bottle is unopened. The spoilage after opening is most often observed to be due to mold which has been assumed to come from infection from the air. As a matter of fact, this is nearly always due to spores which have been held in abeyance, due to lack of air while in the bottle, and which begin growth as soon as conditions are favorable. Spores which fall into the bottle from the air might be unable to germinate upon such a medium, while those already present would.
CHARACTERISTICS OF COMMERCIAL KETCHUP.
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.