592 V. S. BUREAU OF FISHERIES 



liquefaction of ice and consequent absorption of heat can not be at- 

 tained, as it could more nearly be attained if all the warmed brine 

 returning from the fish passed through the salt before it struck the ice 

 and after its passage through the ice chamber went to the fish again. 

 In operation ice and salt are put in their respective chambers and 

 the apparatus is filled with brine. The valves are adjusted to pro- 

 vide the flow of brine and the pump is started. When the proper 

 freezing temperature of brine is reached the fish are put in the freez- 

 ing tank, where they remain until they are frozen. 



Taylor's method 



It is now some 36 years since freezing of fish in direct contact 

 with brine was first proposed. In that time a dozen or more ways 

 of doing it have been brought forward, and activity has been par- 

 ticularly marked in this field in the past 10 years. The advantages 

 and difficulties of brine freezing are now apparent. 



Fish frozen in brine, or by any sufficiently rapid method, undoubt- 

 edly are far superior to air-frozen fish in internal quality, because 

 damage by internal crystallization is avoided, juices are saved on 

 thawing that would be lost from air-frozen fish, autolysis is not so 

 great, and the general appearance of the fish is better. By direct con- 

 tact of brine with the fish the rate of extraction of heat is greater 

 than it is in indirect contact, where the fish are inclosed in containers. 

 Plank 63 has pointed out theoretical reasons for securing rapid freez- 

 ing by direct contact with brine at a moderate temperature with the 

 goods to be frozen, in preference to the very low temperatures of 

 brine not in contact. Also, where contact with brine is immediate 

 there is a sterilization of the surface tissues of the fish that is of prac- 

 tical value. The difficulties arising from penetration have been 

 largely overcome by discovery of the physical principles that govern 

 it and methods of reducing it to a minimum. 



The barriers in the way of widespread adoption of direct brine 

 freezing are largely mechanical. Where tanks are used for immer- 

 sion of fish the volume of brine in proportion to volume of fish is 

 large, almost prohibitively so where very large quantities of fish must 

 be frozen. When fish are immersed in a tank of brine circulation of 

 the main body of brine may be brisk, yet a very slowly moving film of 

 brine will be in immediate contact with the surface of the fish, warm- 

 ing and causing excessive penetration of salt. Fish are of lower 

 specific gravity than the brine, consequently the}' float and get out 

 of the main movement of brine, crowding close together in a mass 

 through which the brine does not circulate freely. In doing this they 

 may also suffer considerable rubbing together, with consequent dam- 

 age to snouts, fins, scales, and tails. Floating massed in brine, the 

 fish assume curved shapes and do not pack advantageously when so 

 frozen. Where fish are frozen in batches (as they are in all tank- 

 freezing methods except Goer de Herve's) the sudden charge of a 

 large quantity of fish with rapid transfer of heat from fish to brine, 

 unavoidably raises the temperature of the brine, with consequent 

 penetration of salt, difficult or impossible glazing, and lack of uni- 

 formity of operation. Brine is corrosive, rapidly accumulating rust 



68 See p. 598. 



