Bacterial composition and succession during storage of North-Atlantic cod (Gadus morhua) at superchilled temperatures

Abstract

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, % CO 2/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 abundant 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. © 2009 Reynisson et al; licensee BioMed Central Ltd.