CANNING OF FISH AND FISH PRODUCTS 429 



excess moisture and supplements the cooking of the fish in the can during the 

 subsequent sterihzing process. In the case of sardines one of two methods is 

 usually followed: the fish are either steamed and dried before packing, or they 

 are dried first and then cooked by a frying process. In some plants a light smoke 

 is given to herring before they are canned as sardines. 



Packing. As most fish products, with the exception of salmon, are practically 

 impossible to pack mechanically, nearly all of them are packed by hand. A tuna- 

 packing device is now in the development stage. This machine cuts and forms 

 the tuna into blocks which are the exact size to fit the cans. The entire procedure 

 is automatic, and the exact weight required to fill the can is contained in the one 

 block. 



Exhausting. In order to insure a proper vacuum in the cans before sealing and 

 to shorten the time required for the sterilizing process it is common in many fish- 

 canning operations to exhaust the cans before they are sealed; this is done by 

 passing them on an endless belt through a steam chamber for a period varying 

 usually from 5 to 15 minutes and at an approximate temperature of 212° F 

 (100° C). 



Sealing. The machines for sealing the cans by rolling the seams have reached 

 such a high degree of perfection that the cans may be sealed at the rate of 200 

 to 300 per minute. 



Sterilization. Is used in this discussion of canning in the broadest sense. Actu- 

 ally canned products are not completely sterilized as meaning that all bacteria 

 are killed. In canning the heat treatment is sufficient to kill only those organisms 

 which would be likely to cause spoilage of the product or be a menace to the 

 health of those consuming it. The time and temperature for the adequate treat- 

 ment of the various products have been carefully determined. In the references to 

 sterilization below the meaning should be given the broad interpretation and 

 considered as synonymous with processing. 



Processing. As canning of food products is based on the principle of sterilizing 

 by heat, the final cooking, or "process" as it is called, is the most vital and im- 

 portant step in the canning procedure. 



On account of the solidity with which fish products are ordinarily packed in 

 cans heat penetration is necessarily slow. In order to secure adequate steriliza- 

 tion within a reasonable time it is customary to sterilize such products in retorts 

 under pressure. A temperature varying from 230 to 240° F (110 to 116° C) is 

 ordinarily used. 



Testing. After the cans have been cooled, it is customary to test them for leaks 

 or defective seams before they are finally packed in cases for shipment. 



Salmon-Canning Industry 



Value and Location. On the basis of dollar value the salmon industry is the 

 largest fish-canning operation in America. The largest production of canned salmon 

 is in Alaska, with Washington and Oregon following in the order named. A few 

 salmon are packed in California. Ordinarily, however, the salmon run in this 

 state is not sufficiently large to support the operation of a cannery. 



During the 1948 season 4,824,966 cases, valued at $120,537,196, were packed 

 in 123 plants in Alaska, 35 in Washington, 14 in Oregon, and 4 in California. 

 Table 92 (p. 430) contains the statistics of the pack. 



