Influence of Freshness and Frozen Storage Temperature on Quality of Thawed Cod Fillets Stored in Modified Atmosphere Packaging

The effects of keeping cod fillets in air at 0°C for 1 or 8 d prior to modified atmosphere packaging (MAP) and subsequent frozen storage at -20°C and -30°C for 6 wk were studied. Quality attributes of thawed MAP cod fillets stored at 2°C for up to 17 d were evaluated. The known specific spoilage organism of fresh MAP cod, Photobacterium phosphoreum, was found in levels of 2.3 and 5.8 Log (cfu/g) after 1 and 8 d of chill storage in air at 0°C, respectively. Frozen storage at both -20°C and -30°C for 6 wk reduced numbers of P. phosphoreum to below the limit of detection. After chill storage at 2°C, P. phosphoreum was not detected in cod fillets stored frozen at -20°C. Significant growth of P. phosphoreum and production of TMA during chill storage at 2°C were only observed in cod fillets kept for 8 d in air at 0°C prior to frozen storage at -30°C. Frozen storage odour and taste developed in thawed MAP cod fillets during chill storage but they were substantially more pronounced in cod fillets stored 8 d in air at 0°C before freezing. The present study clearly showed the need for fresh raw material when producing thawed chilled cod fillets packed in modified atmosphere. Consequently, it was concluded that `frozen at seaʹ raw material in combination with MAP seems to be a promising technology, combining the inhibitory effect on microbial growth and TMA production for the manufacture of prime quality thawed MAP cod fillets for retail.