Title: Methods of pre-cooling for fresh cod (Gadus morhua) and influences on quality during chilled storage at -1.5°C

Author(s): HongYan Gao
Final project
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Cod (Gadus morhua); pre-cooling; quality; chilled-storage; slurry ice; CBC pre-cooling; cooling mats.


In recent years super-chilling and pre-cooling techniques have attracted considerable interest. The aim of this study was to analyse the influences of different pre-cooling methods, i.e slurry ice, CBC (combined blast and contact freezing) and usage of cooling mats, on the quality of fresh cod fillets during further storage at -1.5 ˚C. The objective of this project was to assess the suitability of pre-cooling using CBC as a technique both for whole fish and fillets (or portions). Analysis of variance (ANOVA) was carried out on QDA data in the statistical program NCSS 2000 (NCSS, Utah, USA). PCA (principal component analysis) was performed both for QDA and comparison of measurements in the program Unscrambler (Version 9.5, CAMO Trondheim, Norway). From the CBC pre-cooling experiments an appropriate temperature condition might be concluded as being from -23 ˚C to 20 ˚C for whole cod with an average weight of 1.04 kg when pre-cooled in a CBC freezer for 11 minutes. During the early storage period all of the three different cooling methods slowed down the rate of formation of TVN and TMA spoilage compared to the group without any cooling method applied. The three pre-cooling methods had similar effects on prohibition of growth of bacteria if hygienic handling with slurry ice was performed. The treatment with slurry ice and further chilled storage had an effect on prolonging the process from neutral quality to spoilage with regard to sensory results. Comparison of chemical, microbiological and physical quality parameters of fresh cod showed that TVN, TMA, TVC, pH and H2S producer have good correlations with the evaluation of the quality of fresh cod. 

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