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Gunnar Þórðarson
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gunnar.thordarson@matis.is
The effect of rigor mortis on fillet quality
The purpose of the study was, on the one hand, to investigate the effects of supercooling on freezing and comparing it to conventional refrigeration, and on the other hand to prepare promotional material that could be used to introduce stakeholders in the fisheries sector to the importance of controlling the freezing process. A study was carried out 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 and where 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; supercooled and traditional, and on the other hand to interpret the results for promotional material. 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 within groups indicate a more accurate and credible conclusion. The results show that there is a large difference in the contraction of the fish muscle when it goes through the freezing process, depending on whether it is supercooled or conventional cooling is used. It can be concluded that there is a great quality benefit in the use of supercooling for death stiffness, which reduces contraction and consequently reduces tension between muscles and spine. With too fast and too much contraction of the death stiffness, the muscle can easily be damaged, such as loosening, the stiffness of the fillets decreases, etc.
The purpose of this project was to study the effect of superchilling on rigor mortis process and compare it to traditional chilling with ice. Also to prepare promotional material to enlighten the fishery industry on the importance of managing the process of rigor mortis for product quality. A study was conducted on cod and salmon, including seasonality effect on rigor mortis for cod. The definition on sub chilling in this study is; for cod it is based on cooling to -0.7 ° C and for salmon down to -1.5 ° C and for traditional chilling by ice is targeted at 0 ° C for both species. The rigor process was studied between groups, sub-chilled and traditional, and within groups to investigate standard deviation between samples to sample credibility of outcome. The results indicate a large difference in the contraction process on whether the fish is super chilled or traditional cooling used. The conclusion of the study indicates that sub chilling, which reduces the contraction and consequently the tension between muscle and backbone in the process, can have a large effect on fillet quality, less gaping and a firmer product.