FISH MEAL AND OIL 485 



ing the liquor in a pan. The steam tubes passing through the pan are completely 

 covered with liquor at all times during actual evaporation. 



The pans in which evaporation takes place are enclosed and are operated under 

 reduced pressure, maintained by vacuum pumps and vapor condensation. The 

 first unit is heated by means of low-pressure steam passing through the tubes; 

 usually this is exhaust steam from engines or pumps. Since the liquor to be con- 

 centrated in this unit is under reduced pressure of about 24 inches (600 mm) 

 of mercury, it boils at a lower temperature. As the liquor reaches a predetermined 

 concentration, it is drawn into the second evaporation unit. The vapors from the 

 boiling liquor in the first unit are passed through the steam tubes of the second. 

 The partially concentrated liquor in the second unit continues to boil under an 

 increased vacuum of about 28 inches (700 mm) of mercury, thus further lower- 

 ing the boiling temperature. In the third and last unit the evaporation is completed 

 under reduced pressure of approximately 30 inches (750 mm) of mercury. The 

 vapors from the second evaporation unit boil the liquor drawn over from the 

 second unit into the third unit. 



The valves controlling the flow of liquor from the supply tank into the first 

 evaporator unit and between the other units can be adjusted so that the operation 

 is continuous. A discharge of the finished concentrate of standard density is as- 

 sured by this controlled system. 



When the concentration of the liquor in the third unit reaches approximately 

 50 per cent solids, it is considered finished and passes into storage tanks for 

 future shipment to feed mixers. 



During evaporation the original liquor has been reduced in volume by approxi- 

 mately 90 per cent (i.e., approximately 90 pounds of water has been removed 

 from each 100 originally contained in it). It contains sufficient acid to prevent 

 either bacterial or proteolytic decomposition, even though stored over a consider- 

 able period of time at ordinary temperatures. 



This condensed stickwater is valued by dry-feed mixers for inclusion in mixed 

 animal foods. The moisture content is such that it is readily absorbed by such feed 

 material as alfalfa meal, wheat middlings, etc. without materially afi^ecting the 

 total moisture content of the feed. The high animal protein growth factor contained 

 in it promotes the rapid development of farm animals when it is used as an in- 

 gredient in the feeds. 



Analysis of Condensed Fish Solubles. Sharples-Lassen (1949) have given the 

 following analysis as being typical of condensed fish solubles prepared from 

 pilchard on the basis of 50 per cent total solids: 



Minerals 



% % 



Calcium (Ca) 0.87 Magnesium (Mg) 0.016 



Phosphoms (P) 0.85 Sodium Oxide (Na,0) 1.87 



Iron (Fe) 0.025 Potassium Oxide (K„0) 1.93 



