546 u - s - BUREAU OF FISHERIES 



Circulation of air, especially if rapid, greatly facilitates the freez- 

 ing of fish. Halibut weighing about 15 pounds, suspended before a 

 large fan in the sharp freezer at 9.5° below zero, froze in &y 2 hours. 

 Another experiment with a long wooden tube 2 by 2 by 12 feet long, 

 with a fan at one end and fish suspended in the tube, gave interesting 

 results. The air temperature was 10° below zero. Whitefish nearest 

 the fan were frozen in one-half hour. The air passing over the fish 

 was warmed rapidly, so that fish at the opposite end of the tunnel re- 

 quired three hours to freeze. At 7° above zero smoked fillets of had- 

 dock before a fan froze in 30 to 40 minutes, according to the distance 

 from the fan. The nearest were 6 inches from the fan and the 

 farthest about 18 inches. This method of freezing dries the fish 

 excessively, and, because of the large volume and high velocity of 

 air necessary, seems impracticable for commercial use. About 33 

 cubic feet of air are equivalent in cooling power to 1 pound of brine. 

 The preferred practices to be recommended in the freezing of fish in 

 sharp freezers may be summarized thus : 



1. The sharp freezers should be adjacent to each other or to other cold rooms, 

 and exposed walls, floors, and ceilings should be heavily insulated. 



2. Tight doors should be provided, and the air circulation should be locked 

 with anterooms. 



3. Fish are preferably passed into the freezers through small doors in the 

 main doors. 



4. The freezers should be very heavily piped. 



5. If ammonia is directly expanded in the pipes the latter should be kept 

 flooded with ammonia. 



6. If brine is circulated in the pipes, pipe circuits should be so arranged and 

 pump capacities provided to give very brisk circulation. 



7. The rooms should be cold when the fish are put in. 



8. The fish in pans should not be stacked, but each should rest directly on 

 the pipes. 



9. The temperature of the air in the room should, if possible, never be higher 

 than 0°. 



10. To obtain the proper temperature of the room the brine should be at from 

 10° to 20° below zero. 



GLAZING 



When frozen fish are to be stored, they are exposed more or less to 

 the air. If they are not protected, the oxygen of the air will act on 

 the fats, turning them rancid, and the moisture and perhaps odor and 

 flavor principles will evaporate. To protect the fish from these 

 untoward happenings they must be glazed; that is, the frozen fish 

 must be dipped in cold water, some of which adheres and freezes as 

 an envelope or glaze of ice, completely surrounding the fish. 



REMOVING CAKE FROM FREEZING PAN 



Fish that have been frozen in metal pans stick fast and must be 

 warmed slightly by spraying with or immersing them in water to 

 loosen them. In most cases this is done in one operation by passing 

 the pan containing the frozen cake into the glazing bath. (Fig. 10, 

 p. 533.) In this bath the fish thaw just enough to loosen the pan, 

 which is then taken off. The cake, remaining a moment in the 

 water, is covered with a glaze and is then removed for boxing. 

 When this operation is done carelessly the side of the cake that was 

 on the bottom of the pan is not wetted and therefore not glazed. 



In one freezer a rectangular shower bath is provided at one end of 

 the glazing tank. The pan is passed, upside-down, under this bath, 



