WATER: 3092 g 

 ALEWIFE: 3008 g 



LOSSES: 3e 



ALCALASE 

 30g 



pH CONTROL 



SLUDGE 1649 g 



SUPERNATANT 4451 g 



PROTEIN 320' 

 LIPID 1 



ASH 76 



Figure 12. — Material balance, Run No. III-A-3 : 

 product from alewife. 



soluble 



STEAM 



ALEWIFE: 4540 g 



COOKER 



OIL-_/ 



117 g /CENTRIFUGE 



ALCALASE: 2.32 g 

 TAP WATER 425 g 



pN CONTROL 



DRIP 

 1815g 



STICKWATER 

 2850 g 



DIGESTER 



pH 8.5 



55°C 



4 HOURS 



SCREEN 



PRESS 



PRESS LIQUOR 

 1270 g 



PRESS CAKE 

 2400 g 



SAMPLES 



& LOSSES 



80 g 



HODART 

 MILL 



PRESS CAKE 2320 g 



PROTEIN 563" 

 LIPID 203 

 ASH 80 



SLURRY FEED 

 TO SPRAY ORYER: 5282 g 



PROTEIN 611] 

 LIPID 222 



ASH - I 



Figure 13.— Material balance, Run No. III-APC-3: 

 partially soluble product from alewife press cake. 



Enzymatic hydrolysis. — The fish slurry is hy- 

 drolysed in an agitated jacketed reaction vessel. 

 A minimum of three reaction vessels are used in 

 the plant design so that a constant feed of hy- 

 drolysate to subsequent processing equipment 

 may be maintained. The enzyme of choice is an 

 alkaline protease of Bacillus siibtilis added at a 

 level of 0.1 lb. per 100 lb. of fish. Commercial 

 preparations such as Alcalase of Novo Indus- 

 tries, P-58 of Rohm and Haas or Enzeco ABP 

 of Enzyme Development Corporation may be 

 used. An antioxidant is also added to the di- 

 gestion mixture or is added with the extra water 

 during fish comminution. Propyl gallate at a 

 level of 1.4 g (0.003 lb.) per 100 lb. of fish is 

 recommended. 



The fish slurry is adjusted to about pH 8.5 by 

 adding Ca (OH) 2 at the rate of 0.85 lb. per 100 lb. 

 of fish. The pH is maintained at 8.5 during 

 hydrolysis by the addition of a 5N solution of 

 NaOH via an automatic pH controller. The tem- 

 perature is automatically controlled at 55°C dur- 



ing the 5-hr hydrolysis period. The hydrolysed 

 slurry is acidified to pH 6.5 with H2SO4 as it 

 flows into the centrifuge hold tank. 



Bone feed product. — Bones and scales are sep- 

 arated from the hydrolysis mixture by a vibrat- 

 ing screen as it leaves the reactor. Suspended 

 undigested solids and fine bone particles are then 

 removed by the disc-type centrifuge. The sludge 

 discharge from the centrifuge is combined with 

 the wet bone fraction and conveyed to a rotary 

 steam tube dryer. The dried mixture (10% 

 moisture) is weighed, bagged, and stored as bone 

 meal. 



Fish oil. — The oil discharge stream from the 

 centrifuge is washed with hot water as it flows 

 into a hold tank. The free oil is then separated 

 in a liquid-liquid centrifuge and is later pumped 

 from the collection tank to the fish oil storage 

 tanks. 



23 



