Effects of Technological Parameters and Fishing Ground on Quality Attributes of Thawed, Chilled Cod Fillets Stored in Modified Atmosphere Packaging

Abstract

Effects were studied of various technological parameters and fishing ground on quality attributes of thawed, chilled cod fillets stored in modified atmosphere packaging (MAP). Frozen fillets of Baltic Sea and Barents Sea cod, representing two commercial fishing grounds, were used as raw material. The parameters investigated were: (1) packaging in modified atmosphere during frozen storage, (2) frozen storage period and temperature, (3) fishing ground and chill storage temperature, together with (4) the addition of trimethylamine oxide (TMAO) and sodium chloride (NaCl) to cod fillets before freezing or after freezing and thawing. Application of MAP during frozen storage resulted in a significant increase in the drip loss of thawed, chilled MAP cod fillets but none of the other quality attributes studied were influenced by this treatment. This implies that packaging cod fillets without MAP during frozen storage is more appropriate for manufacturing of thawed chilled MAP cod fillets. During chill storage of thawed MAP Barents Sea fillets previously kept at −30°C for 15 weeks, significant growth of Photobacterium phosphoreum and production of trimethylamine were observed. On the contrary, P. phosphoreum growth and trimethylamine production in thawed and chill-stored MAP Baltic Sea cod fillets were strongly inhibited after as little as 4 weeks of frozen storage at 30°C. Contents of trimethylamine oxide and NaCl were substantially higher in fillets of Barents Sea cod compared to fillets of Baltic Sea cod. Therefore, addition of trimethylamine oxide and NaCl to Baltic Sea cod fillets was evaluated and shown to protect P. phosphoreum against frozen storage inactivation and this explained the observed differences in growth of the spoilage bacteria and trimethylamine production between thawed and chill stored MAP fillets from the two fishing grounds. Despite modest production of trimethylamine in Baltic Sea fillets, this cod raw material was less suitable for production of thawed MAP products due to high drip losses during chill storage.