EFFECT OF ICE STORAGE ON 

 THE CHEMICAL AND NUTRITIVE PROPERTIES OF 

 SOLVENT-EXTRACTED WHOLE FISH-RED HAKE, Urophycis chuss 



David L. Dubrow, Norman L. Brown, E. R. Pariser, 

 Harry Miller, Jr., V. D. Sidwell, and Mary E. Ambrose' 



ABSTRACT 



Because red hake that are to be used in the future production of fish protein concentrate will be caught 

 in quantity, the preservation of the hake during periods of glut will present a problem that possibly can 

 be solved by storage of the hake in ice. 



In our study of this problem, whole red hake were held in ice for 2, 6, 8, and 11 days. Organoleptic 

 tests on the fresh fish showed that they were edible on the 8th day but were not edible on the 11th day. 



Samples of fish were removed during each period of storage and were processed ( 1 ) by f reeze-drying to 

 produce a reference sample (2) by solvent extraction with isopropyl alcohol to produce a fish protein 

 concentrate. Proximate composition, amino acid composition, and nutritive quality were determined 

 comparatively on both of these two kinds of processed samples. 



From the data obtained, we concluded that red hake stored in ice for 8 days are suitable for use in 

 the production of fish protein concentrate and that they would be suitable for this use up to the point 

 of spoilage of the fish, which occurs sometime between 8 and 11 days. 



In the period between the capture and processing: 

 of fish that are to be used in products for human 

 consumption, they must be preserved in a man- 

 ner that maintains their food-grade quality. 

 This requirement applies to the production of 

 fish protein concentrate (FPC) as well as to 

 that of more common fish products. 



The preservation of fish is a problem not only 

 aboard the harvesting vessel but at the shore 

 processing plant as well. The problem ashore 

 becomes especially important during periods of 

 glut when the fresh fish must be held several 

 days before being processed. 



In the manufacture of FPC by the method 

 we use, oil and moisture are removed from the 

 fish with isopropyl alcohol. We therefore in- 

 vestigated the possibility of holding fish in this 

 solvent (Dubrow and Hammerle, 1969). We 

 found the method to be entirely suitable for pe- 

 riods of holding up to 11 days. 



Although storage in isopropyl alcohol was 

 satisfactory, more conventional means of holding 



' National Marine Fisheries Service National Center 

 for Fish Protein Concentrate, College Park, Md. 20740. 



the fish, such as storing them in ice, are likely 

 to be used in commercial operations. During 

 the time fish are held in ice, however, consider- 

 able change may occur in the components of 

 the fish tissue. Endogenous and bacterial en- 

 zymes may break down protein into water-sol- 

 uble and volatile components, causing off-flavors 

 and odors in the fish. In addition, the highly 

 unsaturated lipids of the fish may oxidize rapidly, 

 causing the fish to become rancid. 



While these changes are taking place in iced 

 fish, the water from the melting ice is leaching 

 out some of the compounds that are forming. 

 Furthermore, the subsequent extraction with 

 alcohol during the production of FPC, if ade- 

 quate, removes most of the undesirable com- 

 Ijounds that were not leached out by the melt 

 water. 



Just what effect the enzymatic and oxidative 

 changes have on the various components of the 

 tissues as well as on the nutritive quality of 

 the protein in the finally processed FPC is not 

 known. Accordingly, solubilization of the com- 

 ponents of the fish tissues could alter the com- 

 position of the finally processed FPC. We should 



Manuscript received August 1970. 



FISHERY BULLETIN; VOL. 69, NO. 1. 1971. 



145 



