REFRIGERATION OF FISH 



599 



by a cooling medium. In the same year Douglas and Donald 70 in- 

 vented the freezing of fish and the like by inclosing them in bags, 

 which were put in ice cans and surrounded by water. The whole 

 was frozen together, so that the fish were incased in a block of ice. 



FRIEDRICHS' METHOD 



This idea of freezing fish by putting them in tapered cans and 

 lowering the cans in cold brine, according to the well-known prac- 

 tice of making ice, was revived in 1915 by Martin Friedrichs 71 in 

 Hamburg, Germany. Friedrichs adapted it particularly to the 

 freezing of eels. The eels were hung on a support and lowered into 



Fig. 



34. — Petersen's method of freezing. The panned fish are transferred to 

 freezing molds. Courtesy, Bay City Freezer 



the 



a deep, narrow, tapered can and were surrounded by water. The can 

 was then lowered into an ice-brine tank and the contents frozen 

 solid. When the contents were frozen the can was withdrawn from 

 the brine and the block was removed and stored at a temperature a 

 few degrees below the freezing point of water. It was reported that 

 eels frozen and protected in this way kept perfectly for a year or 

 more. Provided a lower temperature was used in storage, they 

 should keep almost indefinitely. 



Petersen's method 



P. W. Petersen, of Chicago, using a tapered freezing can, worked 

 out many details of its application to the commercial freezing of 



70 British Patent 20014, 1889 (Feb. 8. 1890). 



71 Die Friedriehs'che Aal-Gefriermethode. Die Kalte-Industrie. 

 1/3, pp. 3-4. Hamburg, 1915. 



XII Jahrgang, Heft 



