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

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 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.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.The Atlantic cod (Gadus morhua) is a cold-adapted fish species which has been captured for human consumption for many years. It is a perishable commodity and for that reason, preservation methods like freezing or salting have traditionally been used to extend its shelf life [1,2].The fish is a microbial ecosystem of its own where the ecological principles of succession are as valid as in any other ecosystem. This microbiological environment consists of a high nutrient content with an oxygen tension favourable to the proliferation of fast-growing heterotrophs also responsible for the spoilage of food [3-5]. Until now, the process of fish spoilage has been investigated intensively with regard to sensory evaluation, chemical changes of volatile and non-volatile compounds and microbiological growth by cultivation methods [5-9].Pseudomonas spp.