144 DESCRIPTION OF IMPORTANT FISHERIES AND THEIR PRODUCTS 



It is very important that the temperature of the stickwater is high when 

 it is centrifuged, a temperature of 200 to 205°F being optimal for cen- 

 trifugation. The fraction containing predominantly the oil is pumped to 

 a tank where it is blended with hot water then passed through a so-called 

 polishing centrifuge. In this centrifuge, water and suspended matter are 

 separated from the oil and, when properly adjusted and operated, the oil 

 appearing from this centrifuge is dry and clear and may be pumped 

 directly to crude oil storage. 



The stickwater leaving the centrifuges still contains, as pointed out 

 above, small amounts of oil. This oil, amounting to from 0.5 to 0.9 per 

 cent, is assumed to be so highly dispersed in the aqueous phase of the 

 stickwater and so intimately tied up with proteinaceous material that 

 it is not influenced by the gravitational gradient existing in the centri- 

 fuge. The stickwater is now pumped to the solubles plant where it often 

 undergoes further treatment before it is concentrated, by vacuum evapo- 

 ration, into condensed fish solubles. 



Manufacture of Condensed Fish Solubles. Condensed fish solubles are 

 comparative newcomers to the family of by-products from fish cannery 

 operations. Until the late thirties, the stickwater, as soon as it had been 

 freed of its fish oil content, was discarded and run into the harbor or 

 adjoining waterways. This often caused some very unpleasant water 

 polution problems. 



Table 10.1. Typical Analysis of Condensed Fish Solubles 



