COMPARISON OF SUPERCHILLING AND FREEZING ON THE MICROSTRUCTURE, MUSCLE QUALITY AND PROTEIN DENATURATION OF GRASS CARP (CTENOPHARYNGODON IDELLUS)

Quality changes in grass carp during superchilled storage at -2C were evaluated in terms of the microstructure, drip loss, pH value, total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), water holding capacity (WHC), salt soluble protein (SSP) and Ca2+-ATPase activity by comparison with frozen storage at -18C. The microstructure of grass carp muscle was seriously damaged with the exhibition of myofibril shrinkage and breakage under frozen storage. Both TVB-N and TMA-N contents in superchilled grass carp were controlled under the acceptable values within 21 days of storage. Significant lower drip loss and higher WHC under superchilled storage was observed compared with frozen storage. Superchilling attenuated the denaturation of myofibrillar protein and the damage of muscle structure associated with freezing, where extractability of SSP and Ca2+-ATPase activity were reduced. A shelf life of 21 days for superchilled grass carp could be estimated by the overall quality evaluation. PRACTICAL APPLICATIONSTraditional frozen fish can be extended for a long time. However, large amounts of water frozen out lead to serious texture change and drip loss after thawing. This study evaluated the potential of superchilling technology to keep the quality of grass carp with little damage caused by freezing storage. The results confirmed that superchilled grass carp could maintain the fresh quality up to 3 weeks. The present study provided a possible application of superchilling for medium period storage of freshwater fish.