Summary:
Background
The bacteriology during storage of the North Atlantic cod has been investigated for the past decades using conventional cultivation strategies which have generated large amount of information. This paper presents a study where both conventional cultivation and cultivation independent approaches were used to investigate the bacterial succession during storage of cod loins at chilled and superchilled temperatures.
Results
Unbrined (0.4% NaCl) and brined (2.5% NaCl) cod loins were stored at chilled (0 ° C) and superchilled (-2 and -3.6 ° C) temperatures in air or modified atmosphere (MA, % CO2/ O2/ N2: 49.0 ± 0.6 / 7.4 ± 0.2 / 43.7 ± 0.4). Discrepancy was observed between cultivation enumeration and culture independent methods where the former showed a general dominance of Pseudomonas spp. (up to 59%) while the latter showed a dominance of Photobacterium phosphoreum (up to 100%).
Gas chromatography-mass spectrophotometry (GC-MC) showed that trimethylamine was the most abundantly volatile in mid- and late storage periods. Terminal restriction polymorphism (t-RFLP) analysis showed that the relative abundance of P. phosphoreum increased with storage time.
Conclusion
The present study shows the bacteriological developments on lightly salted or non-salted cod loins during storage at superchilled temperatures. It furthermore confirms the importance of P. phosphoreum as a spoilage organism during storage of cod loins at low temperatures using molecular techniques. The methods used compensate each other, giving more detailed data on bacterial population developments during spoilage.