Tiae of Digestion 



The time necesseiry for conpleting the digestion would of course 

 depend on factors such as, particle size, amount of alkali, and temp- 

 erature of digestion. Shortly after all of the fleshy parts have dis- 

 solved the digestion is considered complete, and the oil readily 

 separates. There is no noticeable advantage in further digestion. Com- 

 parison of the present set. of experiments with those reported by Butler 

 and Miyauchi (2) indicate that increasing the degree of agitation short- 

 ens the digestion time and does not necessarily cause the formation of 

 emulsions . 



SiiTtiTnary 



It is recognized that additional experiments must be performed 

 befoi^ the most efficient procedure can be recommended. However, tho 

 present data are sufficient to indicate a completely satisfactory basic 

 procedure. Studies to impro'/e this basic procedure could best be made 

 using the exact equipment to be operated commercially. 



The present investigation indicates that the whole pink salmon 

 waste should be ground or shredded to break up the head aid collar sec- 

 tion. The digestion retort should be equipped with efficient agitators. 

 The ground material, together with an equal quantity of water containing 

 1-1/2 percent sodium hydroxide by weight, should be heated as rapidly as 

 possible to 190°-200°F. and held at that temperature, with agitation, 

 until the fleshy parts are completely digested, find then a few minutes 

 longer, the total digestion period being approximately 50 minutes. The 

 digested mixture must be allowed to stand for approximately 15 mj.nutes 

 to allow bones to settle and oil to rise. The top layer can then be 

 drained off and passed through a centrifuge. The liquor should not be 

 drained through the bottom of the retort because the oil layer tends 

 to absorb on the solids which have settled to the bottom of the vessel. 



Literature Cited 



(1) BUTLER, Charles, and MIYAUCHI, David 



1947. The preparation of vitamin oils fran salmon cannery offal 

 by the alkali digestion process. Dept. of Commerce, 

 Office of Technical Services report, "Utilization of salmon 

 cannery waste - Part I," Cac-47-17, December. 



(2) AfDERSON, L. 



1945. A preliminary report on an alkali process for the manu- 

 facture of commercial oil from salmon cannery trimmings. 

 Fishery Market News 7, 4-7. 



(3) THE ASSOCIATION OF VITAMIN CHEMISTS 



1947. Methods of vitamin assay. Interscience Publishers, Inc. , 

 New York City, N.Y. 



107 



INT.-DUP. SEC., WASH., D.C. ^89.Jl 



