120 THE FISHING INDUSTRY 



fish, when the protein near the surface becomes coagulated 

 and so prevents the loss of protein from the interior of 

 the fish, or by placing the fish that is to be boiled direct 

 into boiling water, and not into the cold water before 

 the heating has begun. 



In addition to this diminution of the food content of 

 the fish, the process of cooking, contrary to general 

 expectation, also diminishes slightly its digestibility. 



In the canning process the fish to be canned are 

 cleaned (gutted) and boned, and packed into tins, 

 together with the necessary sauce or seasoning. The 

 tins are then closed, a small hole being left temporarily 

 in the lid. The tins are placed on steam-heated racks, 

 and the contents thoroughly cooked. In this way the 

 contents are sterilized as well as cooked, and the air origin- 

 ally present in the tin is all driven out by the steam 

 through the small hole in the lid. This hole is sealed 

 with a spot of solder while the contents of the tin are 

 still at boiling point. The tin and its contents are 

 allowed to cool down, and are dispatched to the store- 

 room. During storage the contents of the sealed tin 

 gradually " mature." This maturing process may last 

 from six months to ten years. During this period 

 the bones soften, the flesh becomes soft and pasty, and 

 the taste becomes richer. The precise nature of the 

 changes that take place during this maturing process is 

 not fully understood ; probably maturing is partly 

 due to the action of certain enzymes in the flesh of the 

 fish, and partly to the slow but continuous chemical 

 action of the various juices present in the tin. Attempts 

 to pickle herrings from the Zuyder Zee have been 

 unsuccessful owing to a lack of the enzyme action that 

 makes other herrings tender when pickled. The 

 enzyme, although present, is apparently rendered inactive 

 by #ie presence of an anti-enzyme. 



