Figure 1. — Experimental system used for fish protein hydrolysis in 5-liter batches. 



isolated a proteolytic yeast which is used to hy- 

 drolyse and preserve fish in a fermentation pro- 

 cess. Batches of red hake, whiting {Merluccius 

 bilinearis), and mullet (Mugil cephahis) were 

 successfully processed in the laboratory. The 

 drum-dried, whole slurry products were rather 

 dark and hygroscopic. Feeding studies indicated 

 that the products were poor as a sole source of 

 protein but were valuable in a supplementary 

 role. Process improvements have since been 

 made by Dr. Bertullo. 



substrate. After cooking and removal of sol- 

 ubles by water extractions, muscle tissue of had- 

 dock (Melanogrammus aeglefinus) was freeze- 

 dried and extracted with ether to yield a powder 

 which was 98 % protein on a moisture-free basis. 

 The hydrolysis conditions employed and the rel- 

 ative proteolytic activities which were measured 

 for the various enzyme preparations are de- 

 scribed in the section on Summary of Experi- 

 mental Results. This phase of work was de- 

 scribed in a publication by Hale (1969). 



Relative activities of commercial enzymes. — 

 A variety of commercially available proteolytic 

 enzjones were collected and compared for rela- 

 tive activity on a specially prepared fish protein 



Whole hake products. — Although tests with 

 the fish muscle substrate showed very large dif- 

 ferences in the relative activities of different 

 proteolytic enzymes, difl^erences were much 



