Abstract: This work was undertaken in order to study the effects of different freezing methods on water state, tissue structure and quality changes of Trachinotus ovatus. Four different freezing methods such as plate freezer (PF), spiral freezer (SF), cryogenic freezer (CF) and ordinary freezer (OF) were used to freeze fresh Trachinotus ovatus. The pH, total volatile basis nitrogen (TVB-N) content, texture profile analysis (TPA) parameters, color difference, water retention capacity (water holding capacity (WHC), cooking loss rate and juice loss rate) of the frozen fish samples were measured and they were also evaluated by low-field nuclear magnetic resonance (LF-NMR) and light microscopy. The results showed that SF samples were generally superior to OF samples in all the parameters tested. The pH and TVB-N content of CF and SF samples were lower, and the TPA parameters, color parameters and water retention capacity changed more slowly than those of PF and OF samples. From the results of LF-NMR, it was found that SF had the least effect on water loss. The observation of muscle tissue microstructure showed the presence of narrow intermyofibrillar space that was evenly distributed as well as small ice crystals, indicating that the quality of Trachinotus ovatus could be well maintained. Therefore, the overall performance of SF was better than the other freezing methods.

Key words: Trachinotus ovatus, freezing method, water, tissue structure, quality