1 82 MEDICAL BACTERIOLOGY 



must be remembered in this connection that most of these are probably non- 

 pathogenic forms, and that 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 manu- 

 facture 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 home-made 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 will still be within permissible limits (25,000,000 

 per cubic centimeter) . Thus for a pulp which must be concentrated one-half the 

 bacterial counts should not exceed about half the limits stated above for the 

 ketchup itself i.e., it should not be more than 12,500,000 per cubic centimeter. 

 The same general rule should also apply to the content of molds and of yeasts. 



To insure a sound product, free from decay or any filthy material, many 

 factors must be carefully watched, for not infrequently oversight in one par- 

 ticular has been found to have undone the good effects of the care exercised in all 

 other ways. Thus it is possible for the washing of the fruit to be ideal and the 

 sorting out or removing of the decayed portions beyond criticism, and yet a 

 delay in making up the pulp into the final product may allow an amount of 

 decomposition to occur which offsets the care previously exercised. It has been 

 a matter of surprise to some manufacturers to find with what rapidity some of 

 these organisms increase. In one factory where this point was tested, the 

 bacterial content in a batch of tomato trimming juice was found to be about 

 7,000,000 per cubic centimeter when taken from the peeling tables, and after 

 standing at room temperature for 5 hours it had increased to 84,000,000. This 

 was a twelvefold increase in a length of time which was less than half the working 

 day for some of the factories visited. At the end of 5 days the number had in- 

 creased to nearly 3,000,000,000 per cubic centimeter. Thus it is seen that delay 

 in manufacture is very liable to result disastrously. 



Such facts as these serve to emphasize the great importance of absolute 

 cleanliness in every detail about factories of this kind. Dirty floors and ceilings 

 and apparatus left with residues of tomato product clinging to them are most 

 fruitful sources for the contamination of new batches of the product. To clean 

 such an establishment properly it is almost imperative that machinery and wood- 

 work be washed by means of live steam used lavishly at frequent intervals. To 

 leave buckets, tables, conveyors, or any other part of the equipment or floors 

 overnight without cleansing them, as was the practice in some factories, is 

 reprehensible and tends to contaminate the product and lead to spoilage and 

 loss.* 



* From Bulletin, Feb. 12, 1911, U. S. Department of Agriculture, "Tomato Ketchup Under 

 the Microscope," by B. J. Howard, Chief, Microchemical Laboratory. 



