Table 13. — Nutritive quality of FPC produced from alewife by enzymatic hydrolysis. 



Standard error of the mean. 



See Table 8 for processing details. 



4.0i- 



3.0- 



2 0- 



0- 



20 



30 



40 

 CHEMICAL SCORE 



50 



60 



Figure 9. — Protein efficiency ratio (PER) versus chem- 

 ical score for enzymatic hydrolysates of red hake and 

 alewife. 



4.0 



3,0 



2,0 



ID 



n 



30 



40 



50 



60 

 EAAI 



70 



80 



Figure 10. — PER versus Essential Amino Acid Index 

 (EA.Al) for fish protein hydrolysates. 



The correlation between PER and essential 

 amino acid index (EAAI) is shown in Figure 

 10. The EAAI is a geometric mean of the essen- 

 tial amino acid concentrations in the sample rel- 

 ative to those in whole egg (limited to 100 9f for 

 those exceeding whole egg) . A good correlation 

 was obtained for the data from the replicate 

 runs, but one product (II-PC-40) and most of 

 the soluble hake products from earlier runs had 

 lower PER for corresponding amino acid indices. 



Both chemical score and EAAI are useful as 

 a general guide to the nutritive value of fish 

 protein hydrolysates, but relatively large vari- 

 ations in PER are found between products with 

 similar scores or indices. One probable reason 

 for the variations is that biological availabilities 

 of the amino acids present are not included in 

 the computations. Also, although the amino acid 

 analysis for whole egg as reported by Block and 



Boiling has generally been used for chemical 

 score calculations, a modified version of it would 

 provide better PER-chemical score correlations. 



Material balances. 



Hydrolysis of red hake. — -Supernatant, 

 sludge, and bone fractions from replicate 6-liter 

 runs were weighed and sampled in order to cal- 

 culate material balances for each process. Ma- 

 terial balances for one run by each of the three 

 processes are summarized in Table 14. Total re- 

 coveries for the pancreatin and Alcalese digests 

 are reasonably good. Note the high concentra- 

 tion of lipids in the sludge fractions relative to 

 the supernates. Also note that about one-half of 

 the ash recovered is soluble ash. The autolysate, 

 II-Aut-2, was spray-dried as a whole slurry after 

 removal of bones and scales. Calculated recov- 

 eries of lipids and ash are excessive. 



21 



