Soluble concentrate. — The aqueous main 

 stream discharge from the centrifuge is col- 

 lected in a hold tank and then concentrated to a 

 dry solids content of about 50% in a wiped-film 

 evaporator. The concentrate is dried in a spray 

 dryer with a secondary bag collector, weighed, 

 bagged, and stored as dry FPC. As an alterna- 

 tive the concentrate from the evaporator may be 

 packaged in 5-gal cans and stored for sale as 

 fish paste. 



Lean fish — Hydrolysates have been prepared 

 from the lean fish, red hake, using a wide variety 

 of enzymes and processing conditions, but we 

 have not yet succeeded in obtaining a totally sol- 

 uble product from hake which is nutritionally 

 equal to casein as a sole source of protein. The 

 recommended process for lean fish, therefore, is 

 one in which a partially soluble product is pre- 

 pared. A satisfactory product with good nutri- 

 tive value has been prepared from hake by autol- 

 ysis without added enzjrmes for a 4-hr period 



at 55° C. The hydrolysis period can be reduced 

 to less than 3 hr by the addition of a low con- 

 centration (e.g., 0.02 lb/100 lb of fish) of an 

 enzyme such as ficin. Digestion at neutral to 

 slightly acid conditions does not require any pH 

 adjustment. 



Referring to Figure 14, the bones and scales 

 are screened out and dried for bone meal, but 

 the sludge discharge from the centrifuge is re- 

 combined with the aqueous stream prior to evap- 

 oration and spray drying. The partially soluble 

 product can be produced quite cheaply since little 

 or no extra enzyme is added, and the yield of 

 product is higher, naturally, when insoluble sol- 

 ids are included. The product is darker in color 

 than the isolated soluble fraction, however, and 

 has a much higher residual fat content. 



Press Cake (Fatty Fish) 



A fish protein concentrate with good nutritive 

 value can ])e produced cheaply through the use 



j-W 



FISH 

 UNLOADING 



WEIGHING 

 CONVEYOR 



190,91 ,. 

 W 



FISH 

 STORAGE 



WATER 

 DUMP 

 TANK 



j-W 



GRINDING 



HOLD 

 TANK 



CHILLER 



SALT 

 STORAGE 



BRINE 

 MAKE UP 



SEA 

 WATER" 



SEA WATER 

 PUMPS 



CITY 

 WATErj 



sw 



DIGESTER 



[NZVME [90.121 

 ANTIOXIDANT |90 13| 

 Ca|0H|2 190,15) 

 H2SO4 190,14) 

 NaOH )9G 17) 



,|91,1| 



VIBRATING 

 SCREEN 



HOLD 

 TANK 



1 



DESLUDGER 

 CENTRIFUGE 



CONVEYOR 



|9I 41 



HOT 

 WATER 



HOLD 

 TANK 



HOLD 

 TANK 



BAROMETRIC 

 CONDENSER 



191,15 



I 



91. E| 



WIPED FILM 

 EVAPORATOR 



191,7 



HOLD 

 TANK 



J 



SCRUBBER 



"T 







ROTARY 



STEAM 



TUBE DRYER 



TaTK^^haust 



^^BAGS 



T 190,3 



WEIGH 



& 



BAG 



BONE MEAL 

 STORAGE 



LIQ LIO 

 CENTRIFUGE 



ZJ 



FISH 

 OIL 

 TANK 



FISH OIL 

 STORAGE 



191.5) 



CANS 



190, 6|_ CANNING 

 ^ MACHINE 



FISH PASTE 

 STORAGE 



ISPRAYDRYERl 



EXHAUST -*-[W 



SCRUBBER 



Figure 14. — Suggested process outline for soluble product from raw fish by enzymatic hydrolysis. 



24 



