Solubles and Liquid Fertilizer 



In many of the tuna canning plants all of the visceral material, 

 including the livers, is collected for use in the production of fish 

 solubles and liquid fish fertilizers. In producing liquid fish fertil- 

 izer one patented process utilizes the naturally occurring enzymes of 

 the entrails to liquify the protein ccmponentSo 



Meal and Oil 



The fins, head, skin, bones and other parts of the precooked tuna 

 which are not suitable for use in the solid, chunk, or flake packs are 

 separated from the edible tuna meat during the cleaning operation. 

 This offal is then conveyed to the reduction plant where it is cooked 

 vrith live steam under pressure and then pressed to expel most of the 

 oil and some of the water. The oil is then separated from the water for 

 marketing as "tuna oil". The water phase (press liquor) containing 

 dissolved protein, water soluble vitamins and minerals, is concentrated 

 in vacuum evaporators to produce fish solubles. The pressed fish 

 material, or presscake, is dried in mechanical dryers to produce fish 

 meal having a moisture content of approximately 8 percent. Tuna meal 

 has a slightly lower protein content than meals prepared from whole 

 fish, such as menhaden, heiring and pilchards. However, it is readily 

 accepted for use as an important ingredient of many animal feeds. 



Efficiency of Use of Offal 



None of the "waste" material from tuna canning operations is 

 discarded. 



Because the head, skin, bones, and other parts removed during the 

 cleaning operation have been cooked (precooking operation) it is not 

 likely that more efficient use can be made of this material than con- 

 version into meal and oilo On the other hand, the viscera, which are 

 removed from the tuna prior to cooking, may be a source of products which 

 are more valuable than those now produced from this material. It is 

 generally accepted that fish viscera represents a potential source of 

 valuable pharmaceutical preparations and other chemical compounds. Some 

 of these products have been prepared from tuna entrails in the labora- 

 tory and on a semi-commercial scale. However, much more investigational 

 work will be required before such products can be profitably produced 

 on an extensive conmercial scale. 



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