A DSC study of phase transition in muscle and oil of the main commercial fish species from the North-Atlantic

- The unfreezable water, melting and glass transition temperatures were measured.
- The fat fraction did not influence the glass transition detection in fish.
- The high temperature glass transition was associated with ice melting.
- The best stability of a fish quality can be achieved at temperatures below − 86 °C.

Phase transitions were investigated for Atlantic Salmon, Cod, Herring, Mackerel and Rainbow Trout. The onset of melting was found between − 33.5 °C and − 29.3 °C. The amount of unfreezable water was calculated by the DSC (differential scanning calorimetry) melting endotherm integration and was in the range between 5.1% and 8.6% for all investigated samples. The low temperature glass transition was determined to be in the range between − 86.0 °C and − 68.0 °C. The high temperature glass transition was found within the melting peak, in the range between − 14.0 °C and − 12.0 °C, and was associated with ice melting. Phase transitions of fats, which were present in the fish muscles, did not influence the detection of low and high temperature glass transitions in the samples of fresh fish investigated. The data obtained could be useful to model the freezing process, especially at temperatures below − 40.0 °C, and the prediction of the fish quality during frozen storage.