Characterisation of the dominant bacterial population in modified atmosphere packaged farmed halibut (Hippoglossus hippoglossus) based on 16S rDNA-DGGE.

It is not well understood why Atlantic halibut (Hippoglossus hippoglossus) has longer shelf-life than most other white fish species. Our approach was to examine the microbiological diversity of the spoilage microbiota during modified atmosphere (MA) packaging of farmed Atlantic halibut. Portions were packaged with gas mixtures of CO(2):N(2) and CO(2):O(2) (50%:50%) and with air as a reference. The packages were stored at 4 degrees C and samples were taken 6 times during the 23 days of storage. Analyses with molecular techniques (PCR-DGGE) determined profiles of the bacterial populations in the various samples and sequencing detected the bacterial species present. In addition, samples were analysed for microbial, chemical and sensory parameters. The shelf-life was 10-13 days when stored in air and between 13 and 20 days for MA packages, with oxygen-enriched packages suggested as the better gas mixture, based on microbial growth and sensory scores. From sequence analyses of the bacterial population Photobacterium phosphoreum and Pseudomonas spp. were found to dominate in the halibut. Brochothrix thermosphacta was found in most samples at the end of the storage period. Shewanella putrefaciens was found sporadically and in low concentrations based on microbial methods, but not detected by PCR-DGGE.