the alkali digestion process is based on the convprsion of proteinaceous 

 matter to a colloidal or semi-liquid state to facilitate separation of the 

 oil in the tissue, this large proportion of protein increases the amount 

 of material to be processed in a ratio disproportionate to any possible 

 oil and/or vitamin A content that could be recovered therefrom. In some 

 of the digestions the testes were, therefore, removed in order to observe 

 the effect of the variation on the processing procedure. 



Processing viscera less gonads with salmon head oil added 



The diluting effect of the head oil has been mentioned before. If 

 there is specific need for oil to act as a solvent for the vitamin A in 

 less oily waste the amount of the dilution may be controlled within the 

 limits deemed most advantageous by the addition of oil previously pre- 

 pared by the alkali digestion of salmon heads. One such test was made. 



Miscellaneous other variables considered 



In Anderson's (l) report there is a list of variables which he found 

 significant, in varying degree, to the proper functioning of the alkali 

 digestion process. In a field study such as this paper describes, not all 

 these suggestions could be checked because of the lack of adequate laboratory 

 facilities at the cannery. At a later date the results of work now in 

 progress at the Ketchikan Laboratory of the Fish and Wildlife Service on 

 some of these factors will be published. At Seldovia the following variables 

 were investigated: 



(1) Particle size. Facilities were not civailable for grinding the 

 salmon heads, but they were chopped to reduce the particle size 

 to approximately 2 inches in diameter principally in the case of 

 king salmon heads weighing 6 to 8 pounds each. 



(2) Amount of alkali. The proportion of sodiiim hydroxide added was 

 varied from 1.5 to 3.0 percent based on the amount of protein 

 present in the waste used. The only criterion for judging the 

 effect of this variation was the difference in the time of di- 

 gestion, consistency of the material at various stages, and the 

 extent of emulsification in the final liquor. 



(3) Temperature of digestion. The effect of the temperature at which 

 the digestions were carried out was noted for 180°, 190°, 200°, 

 and 210O F. 



iU) Effect of sea-water. Digestions were made on material containing 

 sea-water and on similar material washed free of sea-water. 



(5) Effect of blood. The blood was carefully washed from the waste 

 in some digestions, but in others the waste was used exactly as 

 it came from the butchering operation. 



^0 



