224 



FISHERY INDUSTRIAL PRODUCTS 



solids and oil, might be spray-dried to yield a concentrated fish protein 

 for human use. 



Processing Fish by the Wet Process 



World-wide, probably at least 95 per cent of fish meal and oil is manu- 

 factured by a wet process. The various steps involved in this process 

 will be considered separately, including treatment of oil and stickwater. 

 In Figure 16.1, a fiow chart shows the alternative methods of handling 

 encountered in present-day plants. 



I Fishing vessel] — > | Fish pump] — > Dewatering ^ \Na\er 



Foots- 



Quarter box 

 (measure) 



— ezi 



Weighing 

 machine 



Vibratmg 

 screen 



Liquor 



Press liquor 



Screw 

 press 



Cooker 



^ 



Raw box 



T 



Press cake 



i 



Steam - 



Air — 



Gas or fuel oi 



Burner 



Scrap 



Bagging 

 cyclone 



Bog storage i- 



Dryer 



1 Cyclonel ^5H5 >| Deodorizer I > 



-<— Antioxidant 



Curing floor 



Hammer mill 



Blower [ ■ 



►I Bulk 



Scrap 



storage 



-> Truck or freight car to consumer 



Figure 16.1. Flow diagram of production of fish meal, fish 

 scrap, and press liquor by the wet-rendering process. (U.S. 

 Fish and Wildlife Service.) 



Cooking. Most of the fish used are small, less than 10 inches (25 cm) 

 in length, and can be cooked without preliminary chopping. Cooking is 

 necessary to denature the flesh protein and break cell walls so that oil and 

 water can be removed by pressure. Direct steam is usually employed for 

 heating the mass of fish and, in its most common form, the cooker is 

 simply a horizontal cylinder from 15 to as much as 40 feet long and 

 from 15 to 30 inches in diameter with a conveyor screw to move the fish 



