DETERIORATION IN QUALITY OF THAWED FISH IN COLD CHAIN SYSTEM AND THE MECHANISMS OF THE DETERIOLATION

1987 Fiscal Year Final Research Report Summary

• Project/Area Number: 61470138
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: Fisheries chemistry
• Research Institution: TOKYO UNIVERSITY OF FISHERIES
• Principal Investigator: OKUZUMI MASAYO TOKYO UNIVERSITY OF FISHERIES, 水産学部, 教授 (10017030)
• Co-Investigator(Kenkyū-buntansha): HIRANO TOSHIYUKI TOKYO UNIVERSITY OF FISHERIES, 水産学部, 教授 (60017043) ; KOIZUMI CHIAKI TOKYO UNIVERSITY OF FISHERIES, 水産学部, 教授 (80017045) ; MAGAYAMA FUMIO TOKYO UNIVERSITY OF FISHERIES, 水産学部, 教授 (90017020)
• Project Period (FY): 1986 – 1987
• Keywords: Thawed Fish / Cold Chain System / Freshnes / Bacterial Flora / Lipids Non-Protein Nitrogen / β-N-アセチルグルコサミニダーゼ / 脂質類 / 非タン白態窒素

Research Abstract

The present study was undertaken to elucidate the mechanisms of the deteriolation in quality of thawed fish in cold chain system. The experiments were caried out in order to find any differences in the bacterial flora, intercellular enzyme activities, and lipids and non-protein nitrogen contents between the thawed fish and unfrozen fish (control samples). The frozen mackerel stored at -20゜, -30゜, -40゜ and -50゜c, frespectively were thawed with running water at 15゜C and then the fishes were stored at 0゜C. The control samples stored at 0゜C gave off an unpleasant odor after 11 days storage, and the bacterial flora of them consisted of Pseudomonas III/IV-NH, Vibrio, Ps I/II and Moraxella. On the other hand, the thawed fish gave off an odor different from the control samples, and the flora mainly consisted of Ps I/II. Effect of frozen storage process on the viability of the microfora of marine fishes was compared, and the organisms of PsIII/IV-H, PsIII/IV-NH and Vibrio died off much more rap idly than those of the other bacteria. To check on the degree of injury of fish muscle cells by freezing, the activity of <beta>-N-acetylglucosaminidase as a marker was examined using the muscle samples of mackerel, spiny lobster and scallops. It was elucidated that the enzyme is not appreciable to use as a marker. The activity of hypoxantne forming enzyme system of fish muscles was investigated, and the notable results were obtained. Changes in lipids, free aminoacids and ATP of the thawed fish (sardine) muscle during 5゜C and 0゜C storage were studied using GLC, HPLC and TLC. During the storage, the contents of pyosphatidylethanolamine and phosphatidylcholine in control samples decreased more rapidly than those in the experimental samples, but free fatty acids and sterol increased in the experimental ones. The amounts of histidine and ATP in experimental ones decreased much more markedly than those in controle ones. It is considered that the decrease may be depend upon the loss of extracts in the drip from muscle of thawed fish.