CANNING OF FISH AND FISH PRODUCTS 



433 



cooling to keep the ends concave under all conditions of temperature and altitude. 

 Usually the cans are exhausted for 6 to 16 minutes with live steam, having a 

 temperature of 200 to 210° F (93 to 99° C). The hot cans from the "exhaust box" 



TEMPERATURE 

 RECORDER 

 REGULATOR 



AIR OPERATED 



STEAM CONTROL VALVE 



XHECK VALVE 

 SAFETY VALVE 



BAFFLE PLATE 



4-3/4" 

 -WATER LINES 

 KFED BY 2-i'lINES 

 ■SPRING RELIEF VALVE 



-WATER VALVE 



OVERFLOW VALVE 

 -BY- PASS VALVE 

 -WATER VALVE 

 -DRAIN VALVE 



m 



WATER 



STEAM SPREADER 



DRAIN 



(^Courtesy U. S. Fish and Wildlife Service) 



Fig. 20-6. Many of the canning retorts are automatically controlled as to tempera- 

 ture and pressure. This insures efficient operation of the processing. 



pass immediately to the "closing machine" or "double seamer," which rolls the 

 tops on firmly, making the cans airtight. In many of the more modern plants 

 the "exhaust box" has been eliminated by use of the vacuum-closing machine. This 

 speeds up the canning operation to a considerable extent. The cans are rolled into 

 "coolers" or large shallow trays, made of flat, iron strips, each holding several 

 dozen cans. Several of these "coolers" are placed on a small car which is rolled on 

 tracks into retorts for "processing" or cooking by steam under pressure. 



One-pound cans of salmon are usually cooked from 80 to 90 minutes at 240 to 

 245° F (116 to 118.5° C). The 32-pound cans receive a process of about 70 to 75 

 minutes at the same temperature. After processing, the cars are rolled out of the 



