98 DESCRIPTION OF IMPORTANT FISHERIES AND THEIR PRODUCTS 



broth feed (Figure 7.7), and finally under one or more oil feeds. The oil 

 used presently is soya bean or corn oil and is heated to about 180°F. 

 Its addition in the case of solid pack is often made over a long run of 

 line to give the oil time to penetrate the fish before sealing. Solid pack 

 cans may pass over "tippers" to remove excess oil. Either vacuum or 

 steam flow exhaust seamers are used to seal the cans which are then 

 passed through detergent and water washers to remove surface oil. 



In the United States, most tuna is packed in California where all can- 

 ning is under state inspection. Cans must be coded and retorted for a 

 prescribed time in approved and tested retorts fitted with recorders. 

 Records of each lot are examined for conformity by a state inspector 

 who also scrutinizes fish quality and general plant sanitation. 



Data on five sizes of pack in common use are listed below, by far the 

 most popular being the half. 



* Federal Standard of Identity for canned tuna fish\ 

 t Up to 1920, a 307 X 200 can was used. 



By Products. Most larger tuna canneries process ground entrails, 

 cooker water, and scrap from the cleaning operation to give meal, oil, 

 and fish solubles. These operations, for the most part, employ conven- 

 tional cookers, screw presses, and steam tube dryers for meal production ; 

 centrifuges or settling tanks for oil separation; and evaporators for con- 

 centrating solubles. Tuna meal as sold contains 55 to 62 per cent crude 

 protein and around 22 per cent ash which consists mainly of calcium 

 and phosphorus from the high bone inclusion. Viscera, cooker water, and 

 press water from the meal press may be acid or enzyme digested before 

 concentration to finished solubles containing 50 per cent solids. Sulfuric 

 acid is also added at some stage, sometimes to assist in the digestion 

 process, but also to reduce the pH of the finished solubles to a stable 

 level. Oil is removed by centrifuge at one or more stages in varying 

 degrees of purity and is sold both crude and refined. 



