PROCESSING FISH MEAL AND OIL 



231 



process is carried out at about 120 to 140°C for fy^ to 1 hour, followed by 

 filtration. The inferior grade of oil retained by the filter cake can be 

 recovered by solvent extractions^ 



Deodorization of fish oils may be effectively accomplished by steam 

 distillation under reduced pressure. It is important in storage of the de- 

 odorized oils to exclude air because of the great tendency for such refined 

 fish oils to revert or become rancid. This process finds its usefulness in 

 improving the flavor of hydrogenated fish oils for use in shortenings and 

 margarines. Such products are more common in Europe than in North 

 America. 



Fish Solubles 



From the centrifuges the stickwater is usually run to large, temporary 

 holding tanks. Sometimes the hot liquor will be held for 18 to 24 hours, 

 possibly with the addition of enzymes, or until enzyme action and the 



Sfickwoter 



Lossen process 



Acidificolion 

 tonk 



Steom — 

 Enzyme- 



Condensor 

 cooling — 

 woter 



Temporary sloroge 

 tonks 



CenfnfugeJ — > Solids 



Centrifuge I >0\ 



Evoporofor 



Triple effect 

 evoporators 



50% Solubles 



I 



Storoge ond 

 ocid mixing 



Solubles 

 storage tank 



Tank truck, 

 tank car, or barge 

 to consumer 



-Steom 



Acid 

 tank 



Gos or 



fuel oil 



Burner 



LA 



Sproy type 



tiot air 

 evaporator 



Figure 16.5. Flow diagram of production of condensed fish 

 solubles from press liquor. (U.S. Fish and Wildlife Service.) 



normal flora of heat-tolerant bacteria cause a partial breakdown of the 

 protein and a consequent reduction in the viscosity of the finished con- 

 densed solubles. 



As handled in menhaden plants, stickwater is evaporated to the desired 

 concentration before sulphuric acid is added to pH 4 to 4.5, serving solely 



