Table 3. — Approximate costs of proteolytic enzymes per unit of relative activity as de- 

 termined by 24-hr hydrolysis of fish protein. 



Enzyme Source' Approximate Relative Approximate 



cost activity cost 



$/lb. g/g ^/unit 



Pepsin, 1:10,000 Cudahy 16.00 1,000 1.6 



Pepsin, 1:3,000 Wilson 5.15 286 1.8 



Pancreatin, 3XN.F. . . Cudahy 3.50 222 1.6 



Trypsin, 1:80 WUson 4.05 222 1.8 



Panol (papain) EDC 7.00 294 2.4 



Papain Miles 11.00 370 3.0 



Papain Wallerstein 11.50 294 3.9 



Ficin EDC 11.00 167 6.6 



Ficin Mdes 13.50 200 6.8 



Pronase Calbiochem 450.00 1,110 40.0 



' Suppliers of enzymes are listed in the Appendix. 



Effect of cooking on degree of digestion. — A 

 more recent experiment provided quantitative 

 evidence of the effect of cooking on the degree 

 of digestion of hake. Flasks containing equal 

 weights of comminuted hake and distilled water 

 were cooked for 30 min in a 95 °C water bath 

 and then reacted for 5 hr with proteolytic en- 

 zymes added at concentrations of 0, 0.2, 1.0, and 

 5.0% (dry weight basis) . An equal number of 

 flasks containing raw hake slurries were reacted 

 at the same enzyme levels. In phase 1 of the 

 experiment, pancreatin was used at 45 °C with- 

 out pH adjustment. The pH dropped during 

 hydrolysis from pH 7.2 to a lower value depend- 

 ing on enzyme concentration (pH 6.5 minimum) . 

 In the second half of the experiment the added 

 enzyme was Alcalase,* and the pH was main- 

 tained at 9.5 during the 5-hr digestion at 55°C. 

 The hydrolysates were acidified, centrifuged, and 

 gravity filtered at the end of the 5-hr digestion 

 period. The percent recoveries of dissolved sol- 

 ids, crude protein, and tryptophan in the fil- 

 trates, corrected for added enzymes and salts, 

 were plotted versus enzyme concentration for 

 each set of conditions. 



In Figure 4 the yields of dissolved solids from 

 raw and cooked hake are plotted versus the con- 

 centration of pancreatin added. The percent 

 yield from raw hake autolysis (zero enzyme add- 

 ed) could have been obtained from cooked hake 

 by adding about 0.7% enzyme. The normally 

 used concentration of pancreatin, 0.5%, results 

 in a yield under the test conditions of about 11%. 



* Alcalase is an alkaline B. subtilis protease manu- 

 factured by Novo Industries. See Appendix for enzyme 

 listing. 



12 3 4 



ENZYME ADDED. PERCENT [DRY WEIGHT] 



Figure 4. — Yields of soluble solids from raw hake and 

 cooked hake as a function of enzyme concentration. 

 Pancreatin, 5 hr at 45°C, no pH adjustment. 



The second dashed line illustrates that a com- 

 parable yield from cooked hake would require the 

 addition of about 3.1% enzyme. 



In Figure 5 soluble tryptophan recoveries in 

 the filtrates as percent of tryptophan content 

 of the starting material are plotted versus con- 

 centration of Alcalase used at pH 9.5. With no 

 enzyme additions similar yields were obtained 

 from raw and cooked hake. A tryptophan re- 

 covery from cooked hake equivalent to that from 



14 



