DUBROW ET AL. : EFFECT OF ICE STORAGE 



decreased about 15.5'^f within the same period of 

 time. Both glycine and proline increased in 

 percentage of the total amino acid concentra- 

 tion. This increase could possibly be due to 

 the lack of enzymatic breakdown of the fish 

 collagens, thereby increasing the percentage of 

 these amino acids as compared with that of the 

 amino acids of the myofibrillar proteins. 



In retrospect, an analysis of the raw, unpro- 

 cessed fish for free amino acids or total non- 

 protein nitrogen would have made the interpre- 

 tation of these results more certain. 



No marked differences in the amino acid 

 pattern of the standard reference sample could 

 be detected after storing the whole fish in ice 

 for periods up to 11 days. The amino acid pat- 

 tern of the FPC's produced from the same 

 batch of fish as was the standard reference 

 sample, did, however, show changes, which were 

 more pronounced in the FPC processed from 

 11-day-old fish. These changes appeared to be 

 the result of alcohol extraction of solubles that 

 were apparently formed during ice storage and 

 not leached out by the melt water from the ice. 



PROTEIN QUALITY 



Table 6. — Mean weight gained, food consumed, and ad- 

 justed protein efficiency ratio of groups of eight rats fed 

 freeze-dried whole hake prepared from fish stored in 

 ice, compared with casein. 



Storage 

 time 



Meon 

 werghr gained 



Mean weight of 

 food consumed 



Adjusted 



protein 



efficiency 



ratio^ 



^ The protein efficiency ratios were odjusted ta a protein efficiency 

 ratio of 3,00 for casein. 



protein quality of the standard reference sample 

 taken on the 11th day was similar to that of 

 casein and therefore was lower than that of 

 the three samples taken earlier. 



Proximate composition and concentrations of 

 amino acid do not account for the difference ob- 

 tained in the quality of the protein in the 

 sample of fish held in ice for 11 days. Because 

 the fish were from the same lot and were chosen 

 randomly, we can only speculate either that the 

 utilization (digestibility) of the protein (amino 

 acids) was decreased or that compounds de- 

 pressing growth were formed during storage. 



STANDARD REFERENCE SAMPLE 



Protein efficiency ratios were determined by 

 the method of Campbell (1960). Diets of the 

 standard reference samples and of FPC pre- 

 pared from raw fish stored in ice were fed ad 

 libitum to male albino rats (Charles River 

 strain), which were randomly allotted to groups 

 of 10 animals. The samples were added to a 

 basal diet at a 10 ""r level of crude protein. Gain 

 in weight and consumption of food were re- 

 corded each week for 4 weeks, and the protein 

 efficiency ratio was calculated as (weight gain)/' 

 (weight of protein consumed) . A diet in which 

 casein was the source of protein was used as a 

 reference. 



Table 6 shows the data obtained from the 

 animal-feeding studies comparing the quality 

 of the protein of the various samples. Except 

 for the sample jjrepared from fish held 11 days, 

 the protein quality of the standard refei'ence 

 samples was better than that of casein. The 



FISH PROTEIN CONCENTRATE 



The same methods were used to determine 

 protein quality as were used with the freeze- 

 dried fish. 



Table 7 shows the data obtained from the 

 feeding tests made on FPC's produced from 

 the fish held in iced storage. All the FPC's 

 gave a greater gain in weight and a higher pro- 



Table 7. — Mean weight gained, food consumed, and pro- 

 tein efficiency ratio of groups of eight rats fed diets of 

 FPC prepared from raw fish stored in ice for periods 

 up to 11 days compared with casein. 



1 The protein efficiency ratios were adjusted to a protein efficiency 

 ratio of 3.00 for casein. 



149 



