poorer. The pepsin digestion at pH 2 involved 

 fish muscle tissue rather than whole hake. His- 

 tidine recovery was good but yields of protein 

 and tryptophan in the soluble phase were very 

 poor. Digestion of whole hake at pH 8.5 with 

 the alkaline protease gave good yields of protein 

 and tryptophan combined with a fair recovery 

 of histidine. 



Replicate runs, red hake. — Replicate runs 

 were carried out with three different processes 

 using red hake as the feed material. Three 6- 

 liter batches and one 20-gal batch were prepared 

 by each process. Digestion conditions used in 

 these runs and similar runs with alewife, a fat- 

 ty fish, are shown in Table 8. These enzymes 

 and conditions were chosen on the basis of re- 

 sults presented in Tables 5 and 6. Average val- 



ues of yields, proximate analyses, and essential 

 amino acid concentrations for the raw hake and 

 products resulting from each process are listed 

 in Table 9. The high yield and fat content for 

 autolysis is due to the inclusion of insoluble 

 solids. Two feeding trials were carried out with 

 the products of each process. One was with a 

 blend of the spray-dried products from the three 

 6-liter batches and the other was from the 20- 

 gal batch. 



Replicate runs, aletvife. — Three 6-liter batches 

 of alewife, a fatty fish, were hydrolysed by each 

 of three processes and blends of the spray-dried 

 products were used in rat feeding trials. Av- 

 erage values of yields, proximate analyses, and 

 essential amino acid concentrations for the raw 

 alewife and products resulting from each process 



Table 7. — Recovery of histidine, tryptophan, and other amino acids in soluble product and in solubles plus sludge. 



II-PC-Blend Raw hake Pancreatin 



II-PC-40'' Raw hake Pancreatin 



II-A-Blend Raw hake Alcalase 



II-A-40" Raw hake Alcalase 



II-Aut-Blend Raw hake Autolysis 



lI-Aut-40'' Raw hake Autolysis 



III-A-Blend Raw alewife Alcalase 



III-AW-Blend Raw alewife Autolysis 



III-APC-Blend Alewife Alcalase 



Press cake 



° These three products were prepared in 20-gal batches, 

 three 6-liter batches. 



0.50 

 0.50 

 0.35 

 0.35 



0.50 

 0.30 



8.5 

 8.5 

 9.0 

 10.0 

 6.8 

 6.8 

 8.5 

 5.0 

 8.5 



°C 



45 

 45 

 55 

 55 

 55 

 55 

 55 

 55 

 55 



Each of the other products was a blend, after spray drying, of 



18 



