114 U. S. BUEEAU OF FISHERIES 



sufficient time is given to permit the liquors from the center of the 

 cake to reach the outer surfaces. 



(3) The continuous screw press extracts a greater portion of oil 

 and water from cooked menhaden than any of several types of 

 centrifugal equipment tested. 



(4) Menhaden press liquors contain approximately 22 per cent of 

 the total solids of the original material. Of this amount about 17 

 per cent is dissolved materials and about 5 per cent is suspended 

 material. 



(5) Under present operating conditions all dissolved materials are 

 discarded and only about one-third of the suspended materials are 

 recovered. 



(6) In the separation of the oil from the press liquors only about 

 90 per cent of the oil is recovered as first-grade oil, about 2 per cent is 

 lost, and the remaining 8 per cent is recovered in such a manner that 

 it has lost approximately half its value. 



(7) By treating press liquors with a chemical coagulant, such as 

 aluminum sulphate, and passing the liquors through a pressure filter 

 the oil and water emulsion is broken, and all suspended solids and 

 about one-third of the dissolved solids may be recovered. In addi- 

 tion, such treatment may be expected to give a greater oil recovery. 



(8) Approximately 80 per cent of the suspended material may be 

 recovered without difficulty by means of a 60-mesh mechanical screen. 



(9) Screened press liquors may be handled successfully in a me- 

 chancial separator. A similar separator will also recover the oil from 

 the present waste waters. 



(10) Low acid oil may be obtained from fresh gurry by mechanical 

 separators as well as by filter pressing with a filter aid. 



(11) Estimated recovery costs based on the solids content of press 

 liquors and data supplied by manufacturers of evaporators indicate 

 that the possibility of recovering the solids in waste waters warrants 

 the consideration of manufacturers of evaporators and menhaden 

 operators. 



(12) Storing oil in open tanks at the factory causes an increase in 

 the free fatty acid content of the oil. 



(13) The present flame drier used in the industry causes a loss of 

 over 10 per cent of the monetary value of the scrap dried. 



(14) Steam-tube driers will reduce the present loss in monetary 

 value of dried scrap by over 50 per cent. 



(15) Hot dried scrap may be cooled rapidly in an aerator and a 

 portion of the residual heat used for further drying of the material. 



(16) Preliminary feeding tests indicate that steam-dried menhaden 

 meal has greater nutritional value than the flame-dried product. 



(17) The quantity of fat extractable with ether decreases during 

 storage. The rate of the decrease is more rapid in the flame-dried 

 product. 



(18) Menhaden stored at temperatures of from 35° to 40° F. are 

 apparently in as good a condition for reduction purposes after 5 to 6 

 days as fish kept at ordinary summer temperatures for a period of 

 24 hours. 



