CANNED FISHERY PRODUCTS 311 



Drawn aluminum cans, while used almost exclusively in some European 

 countries for fishery products, are not used commercially to any extent 

 at this time for processed fishery products in the United States. This has 

 been primarily due to economics; until recently the price of aluminum 

 has made it unable to compete with tinplate in the United States. This 

 economic picture is changing and within a few years drawn aluminum con- 

 tainers should be used in significant quantities for canned fishery products 

 in the United States. 



Can Making. Open top or sanitary cans for fishery products are made 

 from tinplate sheet ranging in actual gauge from .006 to .0105 inch or in 

 base weight* from No. 55 to No. 95 plate, depending on the size of con- 

 tainer and the process to which it is subjected. 



The stages involved in the manufacture of three-piece open top cans 

 are shown schematically in Figure 24.1. Generally these may be described 

 as follows: Tinplate sheet is enamelled in the flat by passing it through 

 a roll coater and applying a suitable organic protective coating at film 

 weights ranging from two to ten mg per sq in. The enamelled sheet is 

 then slit into body blanks of the proper dimension; the body blanks are 

 fed into a bodymaker which automatically feeds the blanks through a 

 series of stations during which the blank is rolled, notched, fluxed, side 

 seam hooks are formed, engaged, bumped, and soldered. The cylindrical 

 body is conveyed automatically to the flanger which flares out the edges 

 of the body to allow double seaming. The flanged body is fed automati- 

 cally to a double seamer which applies the bottom end of the can at speeds 

 up to 1000 per minute. The finished can is automatically air tested for 

 possible leakers and packaged in bulk shipping cartons, paper bags, or in 

 reshipping cartons, depending upon the request of the packer. 



The steps in end manufacture are also shown in Figure 24.1. The plain 

 or enamelled tinplate sheet is scroll sheared so as to obtain maximum 

 metal utilization. The scroll blanks are placed in a hopper on the end 

 press, the ends punched out and curled. Sealing compound is applied in 

 the channel of the end unit (Figure 24.2) and dried. The finished ends are 

 stacked and wrapped with paper prior to shipment to the packer. 



General Processing Considerations 



The basis of the canning industry has been the development of suitable 

 containers and an adequate process. For our purposes, canning may be 

 defined as the packing of foods in hermetically sealed containers and ob- 

 taining "commercial sterility" through the use of heat processing. Com- 

 mercial sterility, in turn, may be defined as that degree of sterility neces- 



* Base Weight — The weight in pounds of a standard base box of plate of the desired 

 thickness, i.e., the weight of 112 sheets, 14 X 20 inches, 31,360 square inches. 



