Deteriorative Changes During Frozen Storage in Fillets and Minced Flesh of Silver Hake (Merluccius bilinearis) Processed from Round Fish Held in Ice and Refrigerated Sea Water

Abstract

During frozen storage at -10.degree. C, deterioration in muscle of silver hake (M. bilinearis) was marked by rapid and extensive production of dimethylamine, concomitant decrease in extractable protein and by lipid hydrolysis. Evidence of lipid oxidation in this gadoid species of relatively high fat content (2-4%) was also obtained. In minced flesh the rates of deterioration were about twice as fast as in fillets. Holding round fish for up to 6 days in refrigerated sea water (RSW) at 0-1.degree. C before processing extended the frozen storage life of fillets at 10.degree. C by 2-3 wk and of minced flesh by 1 wk over that for comparable materials prepared from round fish held in ice. Materials prepared from winter (March) and summer (Aug.) fish showed little or no difference in rates of deterioration. The susceptibility of silver hake to deterioration at -10.degree. C is similar to cusk; deterioration is faster than in cod or haddock, but not as fast as in red hake (Urophycis chuss). In all silver hake materials negligible deterioration occurred during frozen storage at -26.degree. C for up to 6 mo. During preprocessing storage of round silver hake in RSW, a firm texture and acceptable appearance were retained for several days longer than in round fish held in ice, where objectionable softening of the flesh occurred, particularly in summer-caught fish. Saturation of the sea water with CO2 retarded the onset of bacterial spoilage in RSW-held fish, which otherwise developed more rapidly than in iced fish.