Skaginn / 3X Technology in collaboration with Matís and Westfjords companies working in the fisheries and aquaculture industry, ie Arnarlax and Íslandssaga, with the support of the AVS Fisheries Research Fund, have studied the effects of supercooling on death stiffness in salmon and cod.
Local collaboration on projects that have an impact
The results of the project can be used to increase knowledge about the death stiffness of fish and thus be a contribution to the discussion on increased product quality. It is well known that fish stiffens at the onset of death and is more often than not treated in such a condition, moved between vessels after landing as well as being gutted and cared for. With a large and powerful contraction in the death rigidity, loosening can occur in fillets which reduces the quality of the raw material. It is important to adapt processing to lethal stiffening and control the process to prevent quality loss, such as loosening and poorer texture.
Comparison of conventional cooling and supercooling
The purpose of the study was, on the one hand, to investigate the effect of supercooling on death stiffness and to compare it with conventional cooling. Supercooling is defined as cooling below 0 ° C, but not in such a way that ice crystals form which can damage cells in the raw material. Another purpose of the project was to create promotional material that could be used to introduce stakeholders in the fisheries sector to the importance of managing the mortality process. Until now, death sterilization has been described with photographs and drawings, but in this project the aim was to take advantage of new opportunities for the dissemination of knowledge, such as videos.
The study
A study was conducted on cod and salmon and it was carried out at two different seasons for cod, but there can be great differences in the condition of the raw material depending on when the fish is caught. The study was twofold in that, on the one hand, data were obtained on the effect of cooling on the death solidification process, where the groups were compared; super-chilled and traditional and on the other hand promotional material was prepared.
Supercooling in cod is based on cooling down to -0.8 ° C and salmon at -1.5 ° C, while conventional cooling is based on 0 ° C for both species. Differences between groups were examined as well as comparing differences within groups. Small differences, standard deviations, within groups indicate a more accurate result.
Comparison of the quality of four-day-old salmon fillets, traditional left-hand side and super-chilled right-hand side
results
The results show that there is a large difference in the contraction of the mortality process depending on whether the fish is supercooled or uses conventional cooling. It can be concluded that there are benefits to using supercooling for lethal stiffness, which reduces contractions and consequently reduces tension between muscles and skeletal system in the process.
The results of the project show well the effect of increased cooling on the death solidification process and images can be useful as teaching material and for use in meetings and conferences. Videos of the death-hardening process in salmon and cod were posted on the Internet to distribute them as efficiently as possible.
Discussion
In view of the fact that fillets cut from the spine before death stiffen are significantly shortened beyond the fillets on the spine throughout the process, the question must be answered as to whether this shortening has any effect on the quality of the products. Farmed fish are known to be filleted immediately after slaughter before the freezing process, so it is important to know the effect on taste and texture. It is also important to be able to measure the timing of when the death solidification process ends, but this requires accurate measurements that were outside the scope of this study.
For further information Gunnar Þórðarson, consultant at Matís and station manager for the company in the Westfjords.
Project: The effect of mortality on the quality of fish fillets - (R 16 014-16)