300 PRESERVATION METHODS 



ucts. It is used extensively in fast freezing fishery products packaged in 

 consumer-size cartons and in five- and ten-pound institutional-type car- 

 tons. Among packaged fishery products frozen in the plate freezer are 

 fillets, steaks, shrimp, fish sticks, fish blocks, and scallops. Fish to be 

 plate-frozen should be properly packaged to keep air spaces in the package 

 at an absolute minimum. In addition, during freezing, spacers should be 

 used between the plates to prevent crushing or bulging of the package. 

 For most products the thickness of the spacers should be about 1,32 to 

 f/iQ of an inch less than that of the package. Where very close package 

 tolerances are required, as in the manufacture of fish fillet blocks, a metal 

 tray is employed to hold the packages of fish during freezing. The tray 

 is generally the width of the package and is as long as the width of the 

 freezer plates. 



Contact-plate freezers in commercial use in the United States are of 

 three types: batch, semi-automatic, and automatic. In the batch freezer, 

 as the name implies, products must be loaded manually between the plates 

 and then [removed after freezing. High labor requirements have been 

 reduced by using a specially designed rack of shelves, spaced at the same 

 intervals as the freezer plates to enable transfer of the trays of product 

 to and from the freezer. 



The semi-automatic freezer is similar to the batch freezer, except that 

 it has a mechanism that enables operator-controlled loading and unload- 

 ing of the product. In a typical installation, packaged fish fillets are fed 

 to the freezing unit on a conveyor belt. When a predetermined number 

 of cartons accumulates, the machine operator presses a button, causing 

 a horizontal bar to push the packages off the conveyor into the waiting 

 slot between the two freezer plates. As a row of warm packages enters at 

 the front of the freezer, previously frozen packages advance one row, 

 causing the back row of frozen product to be ejected from the freezer 

 onto a conveyor belt. The product is then conveyed to the freezer. After 

 one plate is loaded, a counting device inactivates the feeder and lifts the 

 freezer plates to the next station, at the same time closing the plates on 

 the product just loaded. The loading cycle is then repeated until all the 

 plates are full. 



The automatic plate freezer is similar to that described above, except 

 that the loading and unloading are controlled automatically by a series 

 of microswitches and electrical relays. In this freezer, the loading time 

 can be varied to suit product freezing requirements. 



Immersion Freezers. Immersion freezers are not standard in design 

 and vary considerably with each application. Fundamentally^, the process 

 involves pumping a continuous stream of brine or other similar refrigerant 

 over the products to be frozen or, in reverse, moving the product through 



