CHAPTER 22 



Fish Meal and Oil 



Introduction 



The reduction of certain species of fish and waste materials from canning and 

 filleting operations is not a recent development in the fishing industry. In early 

 colonial days the need for fats and fertilizer led to the utilization of certain oily 

 or fat species of fish. These products from the fishery resources were obtained by 

 the most primitive methods; however, since then methods and equipment have 

 been perfected and are now highly efficient and economical. At present the profit 

 derived from the conversion of waste products into meal and oil in such operations 

 as filleting and canning often represents the difference between a gain and a 

 loss in the over-all operations of the processor. Methods of fish meal and oil pro- 

 duction are usually based upon the quantity and quality of the material and the 

 condition in which it is received at the by-products plant. Waste materials from 

 the filleting of such nonfatty fish as cod and haddock are processed differently 

 from those received from such oily fish as red perch and herring. The final decision 

 regarding the method to be employed is made by the processor after an examina- 

 tion of several properties: the quantity of material available; the condition of 

 quality (whether or not it is partially decomposed and how far this has pro- 

 ceeded); and the possible oil content. 



Both the wet- and dry-reduction processes are in use. The former is by far the 

 most commonly used in the United States and Canada. Dry reduction is generally 

 more costly to install and operate for the same capacity, and the products obtained 

 are often of inferior quality. Wet reduction is a continuous process and is adapted 

 to large operations, such as the menhaden, herring, and pilchard industries. 



Dry-Reduction Process 



Fishery products to be reduced by the dry process consist principally of waste 

 materials from the filleting of cod, haddock, and halibut heads. The carcasses of 

 grayfish and shark are suitable for dry reduction because of the low fat content. 

 Fish with a high fat or oil content are seldom reduced by this process. 



When the material to be handled is delivered to the reduction plant, it is first 

 put through a grinder or hogger. This serves to break up the large pieces and 

 disintegrate the bones, thus facilitating drying. The ground mass is then loaded 

 into a steam-jacketed dryer through a port at the top. 



The drier is an apparatus composed of a cylinder within a cylinder, separated 

 by a 1- to 3-inch space. A stirring mechanism is fitted through the axis of the 

 apparatus to agitate the material to be dried in the inside cylinder. Live steam 

 under pressure is admitted into the space between the two cylinders, and the 

 mass is agitated by the stirring mechanism during the drying process. This insures 

 a more even drying throughout the mass and prevents scorching. The inside 



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