586 t T . S. BUREAU OF FISHERIES 



mathematical formulae for calculating the freezing points of such 

 mixtures have been studied by Fawsitt. 53 



It is claimed for such a mixture that a temperature as low as 

 25° F. below zero may be attained in practice, and that fish and meat 

 may be frozen in such a brine without impairment of appearance 

 or quality. Ice crystals do not form in the brine under the conditions 

 followed in practice. 



BULL'S METHOD 



H. J. Bull, director of the fisheries research laboratory of the 

 Norske Fiskereies Fremme, at Bergen, Norway, devised a method 5 * 

 of freezing fish in a circular brine tank with an inner chamber, 

 wherein ice is placed. Salt brine is drawn downward through this 

 ice by means of a propeller, and rises in the outer zone. In this 

 latter zone are placed the shelves or baskets of fish to be frozen. 

 He later patented 55 a method of brine-freezing fish by incasing the 

 fish in molds of net or with openwork sides so that the brine could 

 enter and come in contact with the fish. He employed several kinds 

 of molds. One was a shallow wooden frame with sides of wire 

 screen. The fish were packed in the frame, held in place by the 

 screen, and frozen in brine. When the freezing was complete the 

 screens were removed and wooden boards nailed in their stead to 

 the wooden frames, completing a shipping box. Several such frames 

 could be fastened together, making one large shipping package. 

 Bull also used sheet-metal molds and made them of different shapes. 

 From these the frozen cakes were removed and packed in boxes for 

 shipment or storage. 



FYERS's AND WATKINS's METHOD 



In most of the newer methods of freezing fish the aim has been 

 to freeze as rapidly as possible, other considerations generally being 

 subordinated to speed. A. Fyers and W. P. Watkins 56 state that 

 the brine-freezing method involving immersion of fish directly in 

 very cold brine has been unsatisfactory " apparently because of the 

 sudden lowering of the temperature of the fish when immersed in 

 the cold brine." In their method the fish are first thoroughly 

 washed in water preferably at about the normal atmospheric tem- 

 perature. They are then put in a revolving perforated cylindrical 

 drum inclosed in a fixed cylindrical chamber. Around the drum are 

 pipes adapted to spray brine radially inwardly on the drum, so that 

 some of the brine goes through the perforations and strikes the fish. 

 At the beginning the brine is at normal atmospheric temperature, 

 but is gradually lowered until it is at about 15° F., at which tem- 

 perature the fish are treated further until they are frozen. The 

 time required to reduce the temperature to 15° F. is about 2y 2 hours, 

 and the further treatment at 15° is, in the example cited by them, 

 about 2 hours, a total of 4 1 /-? hours. 



33 " The freezing point of solutions, with special reference to solutions containing several 

 solutes," by C. E. Fawsitt. Journal of the Chemical Society. Vol. CXV, 1919, pp. 790-801. 

 M British Patent 23126, Apr. 16, 1913. 

 55 U. S. Patent 1201552, Oct. 17, 1916. 

 M British Patent 127404, 1919. 



