FISHERY INDUSTRIES OF THE UNITED STATES, 1930 115 

 MANUFACTURING FISH OILS OF HIGHER VITAMIN POTENCY 



The interest which has been aroused concerning the use of fish oils 

 in animal feeding suggests that if these oils are suitable for such usage 

 more should be known about the relation which method of manufac- 

 ture bears to nutritional value. Data should be available to guide the 

 fish oil producer in manufacturing an oil conserving as near as pos- 

 sible, its original vitamin potency. With this in mind, an investiga- 

 tion was undertaken to measure the effect of the various operations 

 in the manufacturing process on the vitamin potency of the oil. 



The data obtained as a result of the test work disclosed that the 

 greatest destructive effect on vitamin D during the reduction process 

 can be attributed to the present method of breaking the separated oil 

 emulsion by treatment with heat in the oil cooking tanks. Fish oil 

 manufacturers who desire to produce oil of higher vitamin potency 

 therefore should take steps to eliminate the operation from the factory 

 process. Information obtained during the test work suggested also 

 several methods of manufacturing procedure whereby this could be 

 accomplished. 



The first method requires the use of (a) a mechanical screen to re- 

 move the majority of the suspended solids in the press liquors, (6) a 

 centrifuge which gives a three-phase separation to make a preliminary 

 separation of the oil portion in the presence of fine solids, and (c) a 

 centrifugal oil purifier. 



A second method would require the use of (a) a centrifugal extractor 

 to remove the solids present in the press liquors, (6) a screening ar- 

 rangement to recover the solids removed by the extractor, and (c) a 

 centrifugal oil and water separator to make the final oil and water 

 separation. 



A third method would require (a) immediate filtration of chemically 

 treated press liquors, (b) mechanical separation of the filtered liquor, 

 and (c) mechanical purification of the separated oil. 



A fourth method would require (a) the use of a screen to remove the 

 bulk of the suspended material as the liquor flowed from the press 

 floor, (6) the use of the present system of gravity separating tanks, 

 and (c) a centrifugal separator to remove the oil from the separated 

 emulsion. 



A fifth method would permit the use of the present factory process 

 up to the point where the oil and emulsion is floated to the cooking 

 tanks. The separated oil layer then would be filter pressed to remove 

 fine solids held in emulsion and the oil recovered in a centrifugal oil 

 separator. 



All of the above procedures are applicable to the present wet reduc- 

 tion process as the liquors flow from the press floor. In the case of 

 menhaden oil, application of the above principles was found to yield 

 an oil having a vitamin D potency 25 per cent higher than oil manufac- 

 tured by the present process. 



COOKING AND PRESSING FISH 



Realizing the importance of the cooking and pressing operations in 

 the manufacture of fish oil and fish meal from such fish as menhaden, 

 sardine, and herring, and the waste resulting from salmon, tuna, and 

 mackerel canning operations, bureau technologists, during the past 

 year, undertook a study of certain aspects of the cooking and pressing 



