14 TOMATO KETCHUP UNDER THE MICROSCOPE. 



iii barrels, or in 5 or 6 gallon tin cans; stone jugs and jars or 1-gallon 

 tin cans are also used, but to a much less extent. Manufacturers 

 state that the use of the larger size tin cans is rapidly gaining in 

 favor, while the barrel method is being discarded by the more pro- 

 gressive plants. The cost of these cans ranges at present from 24 to 

 70 cents each, and with care they can be used for from two to four 

 years. From this it is seen that storing in cans is more expensive 

 than in barrels, but a comparison of pulps put up by the two methods 

 after a few months of storage is sufficient to demonstrate the superi- 

 ority of the can method. The examinations made indicate that pulp 

 stored in barrels always shows spoilage to a greater or less degree 

 and possesses more or less of the following characteristics: Gas r 

 sourness, excessive numbers of bacteria and yeasts, certain products 

 of decomposition, and usually a change in color, flavor, and odor. 

 However, in the use of the cheaper and consequently more lightly 

 coated tin cans there is danger of exceeding the content of tin salts; 

 allowed in food products by Food Inspection Decision 126 (300 mg 

 per kilo). The heavier coated and lacquered tins are, therefore, 

 greatly to be preferred for this purpose as the tomato pulp is a 

 product which, due to its acidity, has considerable action on the 

 ordinary tin can. 



In canning the pulp some plants make a practice of processing 

 the cans after the product has been sealed. On the other hand, others 

 say this is unnecessary if the product has been sufficiently concen- 

 trated by boiling and the cans filled while the pulp was boiling hot. 

 direct from the kettles. When this is possible the labor and expense 

 of processing is saved. In some factories the arrangement is such 

 that the product from the kettles must pass quite a distance through 

 pipes into the storage vat from which the cans are filled. This allows 

 considerable cooling and contamination and will cause spoilage unless 

 the cans are processed after sealing. 



o 



