Abstract
In order to clarify the effects of defrosting conditions on the quality of frozen fish, the fillets of carp (Cyprinus carpio) ordinary muscle stored at -5°C for 28 days or -20°C for 3 days were defrosted at 5, 20, 50°C or in a high frequeucy oven. Their K-value (as a chemical index), breaking strength, apparent modulus of elasticity, hardness, cohesiveness and gumminess (as physical indices) were determined.
Preliminary experiments revealed that these indices except cohesiveness were useful for evaluation of the quality of the fillets stored at 5°C. Among them, K-value was found to be the most reliable index of the quality.
When the fillets stored at -5°C for 28 days were defrosted under various conditions, the K-value was the lowest in the fillets defrosted at 5°C, but values of the physical indices were below the limited ones. When the fillets stored at -20°Cfor 3 days were used, the lowest K-value was also obtained in the sample defrosted at 5°C. Higher values of the physical indices obtained on the fillets defrosted at 50°C or in the high frequency oven were attributable to the shrinkage of muscle due to hlgh telnperature. This was supported by the histological observation of defrosted fillets.
