PROCESSING FISH MEAL AND OIL 233 



neither the amount produced in the United States nor the typical propor- 

 tion of added solids from stickwater in whole meals are figures that can 

 be readily obtained. It can be stated that both are closely correlated to 

 the demand and market price of 50 per cent condensed solubles. When 

 the solubles price is less than half the price for meal, the larger amount 

 will go into meal and vice versa. 



The stickwater solids may be added back as raw stick, but rarely are. 

 They are added as partly concentrated — 30 to 35 per cent solids — solubles 

 or as finished solubles. Any of these may be added to the press cake, to 

 the dry scrap, or at some intermediate state, i.e., when the scrap has about 

 20 to 25 per cent moisture. The choice of procedure is usually dictated by 

 the available capacity of the dryers and evaporators and the amounts of 

 solubles solids that are being added. 



Vitamin Oils 



The production of oils having high potency of vitamins A and D from 

 fish livers was a very important and lucrative specialized branch of the 

 fish reduction industry for a number of years, roughly from 1930 to 1945. 

 Then processes for producing the synthetic pure vitamins were developed 

 to the point where the natural sources were unable to compete price-wise, 

 and this industry almost disappeared from the United States. 



However, production of vitamin oils is still important in other parts of 

 the world. In some areas fish livers are still steamed aboard the trawlers, 

 obtaining a crude separation very shortly after the fish are caught. This 

 prevents spoilage of the livers, which results in undesirable flavors in the 

 oil. The crude product is further refined in shore plants to remove small 

 amounts of water and nitrogenous material from the liver tissue. 



Shore plants, in addition to steam cooking, use an alkali digestion proc- 

 ess which makes the tissues completely soluble to permit centrifugal 

 separation of the oiP. 



Some livers have a relatively low oil content, but the oil has a very high 

 vitamin potency (sablefish, tuna, halibut, swordfish, some shark). This 

 type of liver is often treated with a low vitamin A oil (cod for example) 

 which acts as a wash oil to increase the recovery of the high potency oil. 



There has been a recent revival of interest in natural vitamin sources 

 and improvements in processing which may lead to some degree of recovery 

 of vitamin oil processing in the United States. 



Problems in Meal and Oil Processing 



The fish reduction business is not a quick and easy way to get rich. 

 Pitfalls and problems are many. A few of these will be discussed briefly, 

 to alert, if not to warn, the potential investor of some of the hazards that 

 may be encountered. 



