502 MARINE PRODUCTS OF COMMERCE 



cloth bags separated by boards and pressed by a hand-operated screw press. 

 There is considerable loss of oil, but the efficiency compares favorably with the 

 steaming process, or an average of 40 to 50 per cent of the theoretical yield. The 

 refined oil is prepared by the cold process, as mentioned above. The press cake 

 containing the liver residue, water, and beet pulp is dried and sold as cattle feed 

 with high protein content and increased vitamin A and D potency. 



The mechanics of the separation of liver oil by this method is not thoroughly 

 understood. The theory is that the dried beet pulp has such a sufficiently high 

 affinity for the water in the livers that it can break the emulsion of oil in the cells 

 and absorb the water. 



Cod Oil. The previous discussion has been limited entirely to cod-liver oil 

 as it is used for pharmaceutical pvirposes. A second grade of cod-liver oil, known 

 as "cod oil," is a recognized item in the fish-oil trade. It is usually a dark-colored 

 oil with a disagreeable odor, and is prepared from cod livers which have partially 

 or completely decomposed. 



This grade of oil finds a market in those industries where fish body oil of all 

 species is used. Much of the cod oil is used in the leather-tanning industry, and 

 is often sulfonated for this purpose. As a "currying" oil it softens and lubricates the 

 leather fibers. It is also used in the manufacture of paints, varnish, printing inks, 

 oilcloth, and linoleum. The steel industry uses it for tempering springs and other 

 articles made of steel. 



Very little cod-liver oil of either the medicinal or lower grade is extracted in the 

 United States. Practically all the oil used in this country is imported from either 

 Canada or Iceland, and small quantities are brought from Norway. Medicinal oil 

 is imported as a crude grade and the refining is done by the various users of this 

 grade of oil. 



Nutritional Value of Extracted Cod-Liver Residue 



It has long been recognized that the pulp, or fibrous material remaining after 

 the oil has been extracted from cod livers is a valuable ingredient for inclusion 

 in animal feeds. And while no analyses are available on commercially prepared 

 meals, Guttman (1950) has published analyses on laboratory samples. He found 

 that the average properties of this meal or residue pulp contained the following 

 ingredients: 



Moisture 5.1 Per cent 



Total nitrogen 10.7 Per cent (moisture and oil free basis) 



Free amino acids 4.0 Per cent (expressed in nitrogen) 



Ash 7.6 Per cent 



Copper 0.00033 Per cent 



Iron 0.02 Per cent 



Vitamin Bj 2.7 mg. per lb. 



Vitamin Bj (riboflavin) 18.0 mg. per lb. 



Niacin 50.0 mg. per lb. 



Pantothenic acid 18.0 mg. per lb. 



Total APF activity 1.4 mg. per lb. 



He estimates that at the present price of 20 cents per mg., the APF activity 

 alone is worth $560 per ton when calculated on this basis, disregarding the other 

 valuable nutritional factors. 



