518 FOOD PRESERVATION 
frequently present in such products, such as particles of clay, ete. A 
comparison of this method with the ordinary cultural methods on 
samples in which the organisms had not been killed has almost invari- 
ably shown that the one used gives too low instead of too high results. 
In some cases it was found to give not more than one-third of the entire 
number present. The estimates of the laboratory on this point may, 
therefore, be considered, very conservative. 
As regards the limits which may be expected in the examination of 
ketchups for bacteria, it might be stated that some manufactured 
samples as well as good, clean products made by household methods, 
have been examined and the count found to be so low when estimated 
by this method that the numbers present were reported as negligible. 
In other words, it was found that for the areas counted over the number 
of bacteria averaged less than one—that is, less than 2,400,000 per cubic 
centimeter. It is unusual, however, for the final number per cubic 
centimeter to be less than from 2,000,000 to 10,000,000 organisms. 
Contrasted with this number as a minimum, it has been found that the 
number has occasionally exceeded 300,000,000 per cubic centimeter. 
Such a number as this would indicate extremely bad conditions and 
carelessness in handling, as the studies of factory conditions have shown 
that there is little excuse for the number ever exceeding 25,000,000 per 
cubic centimeter. While experiments have also shown that although 
the effect produced by the bacteria on the product varies with different 
species, it is true that their presence can frequently be detected in the 
raw pulp by odor or taste when the number exceeds 25,000,000 per cubic 
centimeter and sometimes when the count is as low as 10,000,000. 
To one who has not been initiated into the mysteries of the micro- 
scope the presence of such a number of bacteria in a food product 
seems inexcusable. It must be remembered in this connection that the 
most of these are probably nonpathogenic forms, and many occur 
naturally on the skins of the fruits. It does not seem just to set a 
standard so high as to virtually prohibit the manufacture of the product 
under commercial conditions; rather the idea is to set a limit that the 
manufacturer can attain if due care is exercised and which will insure 
a cleanly product. It is, however, perfectly possible to make a cleanly, 
wholesome product commercially even though the number of bacteria 
exceed that in the homemade article. 
The allowable limits for the bacterial content of tomato pulp vary 
according to the concentration. The number, however, should be 
low enough so that when the amount of concentrating necessary for 
its conversion into ketchup has been accomplished the final product 
