Title: Conservation of fresh golden redfish (Sebastes marinus) fillets: influence of bleeding, modified atmosphare packaging using different gas mixtures and superchilling on quality deterioration

Author(s): Alisa Martin
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The objective of this study was to evaluate the influence of bleeding, modified atmosphere packaging (MAP) and superchilling on freshness deterioration and sensory shelf life of redfish (Sebastes marinus) deskinned fillets. Changes in psychrotrophic microorganisms (TVC), specific spoilage organisms (SSO), their metabolites (TMA, TVB-N), pH, drip loss, headspace gas composition, and sensory characteristics (Torry freshness score and texture) were analysed. The pre-trial conducted involved four gas mixtures as well as vacuum packaging (VP) and air (A) storage at -0.4°C to select the most effective packaging method. The VP fish deteriorated fastest, followed by A treatment. All MAP treatments showed a similar inhibitive effect towards the SSO investigated. The lower (40%) concentration of CO2 was sufficient to delay SSO growth but the gas to fish ratio of 2.2-2.5 caused some textural problems. The initial quality of the fillets obtained for the pre-trial varied in redness and bruises, affecting the sensory assessment, and resulted in some differences within treatments. For the shelf study, unbled deskinned fillets stored in air were compared to two MAP treatments and to bled air-stored (AB) fillets during storage for 6 days at -1°C and +2°C, thereafter mimicking distribution via sea freight to European markets. Bleeding of the whole fish resulted in fillets with slightly slower TVB-N and TMA formation due to slower growth of Photobacterium phosphoreum, an important spoilage bacterium in cold water marine fish. Low pH in MAP fillets resulted in higher drip loss but a lower gas to fish ratio reduced texture problems. P. phosphoreum and pseudomonads were the main SSO in MAP and air storage respectively. MAP led to an extension of freshness and shelf life by few days.

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