DUBROW ET AL, : EFFECT OF ICE STORAGE 



Table 2. — Proximate composition of freeze-dried, ground 

 whole hake (standard reference samples) stored in ice 

 for periods up to 11 days. 



Storage 

 time 



Volatiles 



Lipids! 



Ash' 



Crude 

 protein^ 



Days 

 2 

 6 

 8 

 11 



3.80 

 2.49 

 2.46 

 4.70 



»■(. % 

 15.30 

 14.06 

 14.34 

 15.07 



in. % 



13.44 

 12.84 

 12.43 

 12.49 



(ff. % 

 74.47 

 77.34 

 77.38 

 77.01 



' The data on lipids, osh, and protein were based on the dry weight 

 of sample. 



2 Crude protein was calculated as N X 0.25. 



the various samples of freeze-dried whole fish. 

 Data are presented on a dry-weight basis to re- 

 veal possible losses during storage. 



The concentration of lipid varied between 14 

 andl5';r; that of ash, between 12 and 13^c. The 

 data indicate that the nitrogen fraction did not 

 change greatly. The crude protein remained rel- 

 atively constant at about 77 Sr (on a dry- weight 

 basis) except on the second day of sampling. 

 This deviation on the second day was probably 

 the result of a sampling error. Analyses for 

 nonprotein nitrogen would have been helpful 

 for interpretive purposes. Unfortunately, they 

 were not made. Dassow" has reported that the 

 nonprotein nitrogen fraction of whole Pacific 

 hake stored in ice did not change significantly 

 over a period of 11 days. 



Fish Protein Concentrate 



From the remaining portion of each lot of 

 fish, 20 lb were selected at random and were ex- 

 tracted with isopropyl alcohol according to 

 established procedures (Brown and Miller, 

 1969). In brief, the fish were ground through 

 a Hobart meat grinder, were slurried with 15 

 liters of 91% (v/v) isopropyl alcohol for 30 

 min, and were centrifuged. The centrifuged 

 solids were then extracted continuously with hot 

 isopropyl alcohol at 60° to 70° C and at a rate 

 of flow of 0.2 gal per minute. After 2 hr the 

 solids were removed by centrifugation and were 

 desolventized under vacuum at 60° C. 



= Dassow, John A. 1966. Statement of project ac- 

 complishment, Utilization of fishery resources program. 

 In Quarterly progress report of the BCF Technological 

 Laboratory, Seattle, Wash., July 1 - September 30, 1966. 

 Unpublished report, 6 p. 



This method of processing was not intended 

 to be representative of commercial methods. It 

 was used in our laboratory at that time solely 

 as an experimental technique to evaluate selected 

 variables in the preparation of FPC by solvent 

 extraction. It has since been replaced by a sev- 

 eral-stage countercurrent extraction system, 

 which is both much more economical in the vol- 

 ume of solvent needed and is more representa- 

 tive of commercial processing methods. A com- 

 parison of FPC made by each system has shown 

 no significant differences, however, either in 

 chemical composition or in nutritive value. 



The proximate composition was determined 

 by the same method used with the freeze-dried 

 fish. 



Table 3 lists the proximate compositions of the 

 FPC's prepared from the fish stored in ice for 

 various periods. The concentrations of lipids 



Table 3. — Proximate composition of FPC prepared from 

 raw fish stored in ice for periods up to 11 days. 



! The dato on lipids, ash, and protein were based on the dry weight 

 of sample. 



- Crude protein was calculated as N X 6.25. 



and volatiles remained essentially unafi'ected by 

 storage. The concentration of ash increased, 

 however, and that of protein (that is, of nitro- 

 gen) decreased. The major change occurred 

 after the 8th day of storage. Because the con- 

 centration of protein in the standard reference 

 samples did not drop in the same manner as 

 the concentration of protein did in the FPC's, 

 the loss of protein could not have occurred dur- 

 ing storage but must have occurred during pro- 

 cessing. This conclusion could be accounted for 

 by the formation, during storage, of soluble ni- 

 trogenous products resulting from enzymatic 

 breakdown or bacterial breakdown, or from 

 both, that were not leached out of the fish during 

 storage but that were subsequently leached out 

 during the extraction process used in making 

 the FPC. This conclusion was further support- 



147 



