THE SARDINE, MACKEREL, AND HERRING FISHERIES 145 



When it was found that stickwater was a rich source of the B complex 

 vitamins and other growth-promoting factors, a method was developed 

 for its recovery and preservation. This method involved a stabilization 

 of the stickwater by proper pH adjustment and a concentration, by 

 vacuum evaporation, of the dilute liquid into a brown semi-viscous 

 liquid. In stabilizing the stickwater by pH adjustment, small amounts of 

 coagulable proteins are precipitated, and a change in the colloidal prop- 

 erties of the remaining fish oil takes place so that a subsequent centrifuga- 

 tion often yields additional oil and makes the stickwater more suitable 

 for the subsequent concentration in the vacuum pans. This procedure 

 also makes the resultant condensed fish solubles more attractive to the 

 feedstuff mills that use it since it mixes more readily with the other feed 

 ingredients and produces a more stable end product. 



The production of condensed fish solubles in the United States amounts 

 to, at present, more than 200 million pounds a year. Of this total, the 

 sardine and mackerel canners produce only a small percentage. Condensed 

 fish solubles are usually sold in tank car lots of roughly forty tons. A 

 typical analysis of condensed solubles is given in Table 10.1. 



