4 BULLETIN 635, U. S. DEPARTMENT OF AGRICULTURE. 



These pipes are usually direct expansion pipes from the ammonia 

 refrigerating plant. They are so arranged that they make a series 

 of shelves one above the other, each consisting of numerous pipes. 

 Passageways are left between each set of shelves for the convenient 

 handling of trucks. Some plants have installed mechanical con- 

 veyors to facilitate carrying the fish to and from the fish-freezing 

 rooms. 



The operators remove the frozen fish from the pan by pouring a 

 little cold water on the outside of the pan, which causes sufficient 

 melting to allow the frozen fish to slip out in a block. Fish which 

 are to be frozen separately are laid on thin metal sheets resting on 

 the cold pipes, or they are suspended in the air from iron rods or 

 hooks. Fish, single or panned, freeze thoroughly in from 12 to 30 

 hours,, according to their size and the temperature of the freezing 

 room. 



FREEZING IN ICE OR IN BRINE. 



The older method of freezing fish by packing them in covered pans 

 which then are buried in ice and salt still is practiced in some dis- 

 tricts. This plan is not adapted to freezing fish rapidly on a large 

 scale and does not lend itself to accurate control of temperature. 

 Methods of freezing fish in saturated salt brine, cooled to low tem- 

 peratures by freezing coils, recently have been patented. The salt 

 in brine chilled almost to its freezing point apparently does not pene- 

 trate into the fish to any great extent, and freezing is much more 

 rapid than in air. These processes have great merit from the theo- 

 retical point of view, and appear to be adapted to commercial condi- 

 tions, but as yet they have not been adopted by the trade in this 

 country. 



GLAZING. 



Glazing, an important step in the freezing of fish, is designed to 

 incase each fish or each block of frozen fish with an air-tight pro- 

 tective envelope or cover of clear ice. Unless glazed, the skins of 

 frozen fish are liable to turn white and the fish themselves will 

 shrivel because of loss of moisture which takes place even at freezing 

 temperatures. Noses and fins of frozen fish, unless protected by 

 glazing, are the first points to show the effect of loss of moisture. 

 Glazing also helps to prevent the eyes of the fish from becoming 

 opaque and shrunken and to obviate deterioration which makes the 

 gills, which normally are bright red, darker and brownish. Glazing 

 prevents the evaporation of the moisture from the flesh of the fish, 

 prevents the entrance of air which tends to make the fish oils dete- 

 riorate, provides an ice surface upon which molds and fungi can not 

 grow, and finally helps to protect the fish from mechanical injuries 

 which mar its appearance. 



