Condition of Newfoundland Trap-Caught Cod and Its Influence on Quality After Single and Double Freezing

Quality assessments, based on organoleptic evaluations and chemical tests, were conducted before and after cold storage, on trap-caught cod (Gadus morhua) which was unfrozen, once-frozen, or twice-frozen. The cod was processed both before and during rigor, after icing or after handling without ice,...

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Bibliographic Details
Published in:Journal of the Fisheries Research Board of Canada
Main Authors: MacCallum, W. A., Jaffray, June I., Churchill, D. N., Idler, D. R.
Format: Article in Journal/Newspaper
Language:English
Published: Canadian Science Publishing 1968
Subjects:
Online Access:http://dx.doi.org/10.1139/f68-067
http://www.nrcresearchpress.com/doi/pdf/10.1139/f68-067
Description
Summary:Quality assessments, based on organoleptic evaluations and chemical tests, were conducted before and after cold storage, on trap-caught cod (Gadus morhua) which was unfrozen, once-frozen, or twice-frozen. The cod was processed both before and during rigor, after icing or after handling without ice, at various times during the catching season.Lactate determinations and pH measurements on whole fish at killing showed a seasonal variation. There was a correlation between lactate determinations and pH measurements in freshly killed and freshly frozen fillets that had been frozen both before and during rigor. Icing immediately after killing slowed the rate of lactate accumulation.Differences in the state of pre- and in-rigor chilled fish at freezing, as assessed by muscle glycogen, lactate, and reserves of ATP, resulted in differences in texture, thaw-drip, and pH. Patterns in texture may be predicted by the amounts of thaw-drip and the pH measured in the cold-stored pack.Intensity of mealiness and short-grained features in freshly frozen (once) fish was correlated with the level of ATP immediately before cooking. Fillets frozen before rigor toughened very slowly in storage at −23 C and the mealy condition eventually disappeared. Hence, fish downgraded for mealiness at freezing improved or maintained initial overall texture scores during 6 months in storage. Although the panel showed a clear preference for fish frozen pre-rigor, it would be impossible for industry to freeze more than a portion of the landings pre-rigor. To obtain the next best once-frozen product, chilled in-rigor fish should be processed.Double freezing gave the next best product from chilled, prerigor fish. Fish frozen pre-rigor in the "dressed" condition and stored at −23 C, then thawed, processed, and refrozen at 16 weeks, was equal in quality to once-frozen controls. The texture in the twice-frozen material prepared from iced, prerigor frozen fish dropped after a further 10 weeks storage, making it little better than the twice-frozen product of ...