CANNED FISHERY PRODUCTS 321 



It is also important that cans are stacked or jumble packed into the 

 crates so that free circulation of steam is possible; otherwise, low 

 temperature regions or ''cold spots" will develop. 



Vents, large valve-controlled openings, necessary to eliminate air from 

 the retort during the ''come-up" period; i.e., as the retort comes up 

 to the desired processing temperature. The number and placement 

 of vents vary with retort size and design and should be studied care- 

 fully. Proper venting is of extreme importance in obtaining accurate 

 processing temperatures. Retorts are normally vented until the re- 

 tort temperature reaches 215 to 220°F, at which time the valves are 

 closed and the processing cycle is begun. 



Bleeders, small valve openings in the retort usually ^s inch in size, 

 left open during the entire process to assure steam flow. 



Steam Spreaders to allow uniform distribution of steam throughout the 

 retort. 



Drain Valves to allow rapid removal of water from the retort following 

 cooling. 



By-Pass steam valve to allow manual operation of retort during the 

 come-up and cooling cycles and in case of failure of the automatic 

 controller. 



Safety or blow-off valve to prevent excessive pressure in the retort. 



As mentioned early in this chapter, the development of adequate proc- 

 essing techniques and equipment was the basis of the canning industry. 

 A typical processing is described briefly for information purposes, but it 

 is important to remember that only recommended processes and tech- 

 niques such as those recommended in the N.C. A. Bulletin 26L be followed. 



After the cans have been filled and closed, they should be processed or 

 retorted as soon as possible to preclude excessive bacterial growth and 

 product degradation. The cans are then stacked or jumble packed in re- 

 tort crates and the crates placed in the retort. The retort door or cover is 

 closed, sealed, and the steam turned on. The drain valve is closed, and 

 the vents and bleeders are left wide open. As the retort reaches 220°F, 

 the venting portion of the cycle is complete so the vents are closed, the 

 by-pass valve is closed, and the automatic controller put into operation. 



The come-up part of the cycle is completed when the retort reaches the 

 prescribed processing temperature. The process is then begun for the 

 recommended time; for example, 75 minutes at 240°F for 307 X 201.25 

 cans of salmon. At the end of the recommended process time, the auto- 

 matic controller is turned off, the vent to the outside is opened, and 

 cooling water is allowed to enter the retort. After the cans reach about 

 110 to 120°F (warm to touch), the drain valve is opened and the cans 



