Growth and spoilage metabolites production of a mesophilic Aeromonas salmonicida strain in Atlantic salmon ( Salmo salar L.) during cold storage in modified atmosphere

Abstract

Aims The aim of the study was to quantify the growth kinetic parameters and spoilage‐associated metabolites of an inoculated strain of Aeromonas salmonicida in pre‐rigor filleted Atlantic salmon (Salmo salar L.) stored in vacuum (VP) or modified atmosphere (MAP 60/40% CO2/N2) at 4 and 8°C. Methods and Results The maximum growth rate of A. salmonicida in VP salmon stored at 4°C was 0·56 ± 0·04 day−1 with no detectable lag‐phase and the concentration of Aeromonas reached 8·33 log CFU per g after 10 days. The growth rates and maximum population density of Aeromonas in MAP salmon were lower but the applied atmosphere did not inhibit the growth. A selection of metabolites associated with fish spoilage were quantified using 1H nuclear magnetic resonance (NMR) spectroscopy. The concentration of trimethylamine (TMA) was significantly affected by storage time and temperature, packaging atmosphere and inoculation with A. salmonicida (General Linear Model (GLM), P < 0·001 for all factors). Conclusion The study presents preliminary results on A. salmonicida as a potential spoilage organism in vacuum‐packaged salmon during cold storage. The combination of refrigeration and a packaging atmosphere consisting of 60/40 % CO2/N2 did not completely inhibit the growth but prevented the formation of TMA. Significance and Impact of the Study Little information is available on the spoilage potential of Aeromonas spp. in minimally processed salmon products under different packaging conditions. The study clearly demonstrates the importance of hurdle technology and provides data to further elucidate the significance of Aeromonas spp. as a spoilage organism.

Spoilage‐related microbiota in fish and crustaceans during storage: Research progress and future trends

“…A timely supplement to CO 2 absorbed by food matrixes could also be beneficial for improving the preservative effect (Tsironi et al., 2019). As for common spoilage bacteria in air‐packed fishery products, Aeromonas and Shewanella are usually more resistant to CO 2 than Pseudomonas and can keep slow growth in MAP conditions (Antunes‐Rohling, Artaiz, et al., 2019; Jakobsen, Shumilina, Lied, & Hoel, 2020; Zhang et al., 2019). The viability of Aeromonas and Shewanella in MAP may be due to the existence of facultative anaerobic species/mutants, which suggests us to study the microbiota isolated from MAP products at species/strain‐level.…”

Growth and Spoilage Potential of an Aeromonas salmonicida Strain in Refrigerated Atlantic Cod (Gadus morhua) Stored under Various Modified Atmospheres

“…The initial concentration of the inoculated strain quantified on SAA averaged log 5.1 ± 0.1 CFU/g. The relatively high concentration of inoculum was applied to increase the likelihood of detection of metabolites in a naturally contaminated system, as previously described in Jakobsen et al [ 30 ] and Lerfall et al [ 42 ]. The combination of MA (balanced with either O 2 or N 2 ) and refrigeration (4 °C) inhibited the growth of A. salmonicida in the cod fillet during 13 days of storage ( Figure 2 a).…”

“…Vacuum packaging allowed the growth of the inoculated strain, and the concentration of Aeromonas increased by almost 3 log units to 7.7 ± 0.32 log CFU/g during storage. The lag phase (3.4 ± 0.66 days), estimated by fitting the data to the primary growth model of Baranyi and Roberts [ 37 ], was longer than observed for the same strain in salmon under comparable conditions [ 30 ]. The maximum growth rate of the inoculated A. salmonicida SU strain quantified on SAA in the present study was almost two times higher in cod (µ max = 1.00 ± 0.38 log CFU/day) compared to the rate previously reported in salmon (µ max = 0.56 ± 0.04 log CFU/g/day) [ 30 ].…”

“…The lag phase (3.4 ± 0.66 days), estimated by fitting the data to the primary growth model of Baranyi and Roberts [ 37 ], was longer than observed for the same strain in salmon under comparable conditions [ 30 ]. The maximum growth rate of the inoculated A. salmonicida SU strain quantified on SAA in the present study was almost two times higher in cod (µ max = 1.00 ± 0.38 log CFU/day) compared to the rate previously reported in salmon (µ max = 0.56 ± 0.04 log CFU/g/day) [ 30 ]. However, when comparing the growth curves for the inoculated strain quantified on SAA to the curve derived from IA, it was apparent that the inoculated culture was somewhat inhibited during the first two days, possibly from selective conditions in the SAA, resulting in a steeper slope from day two and onwards ( Figure 2 a).…”

“…Inoculation studies have demonstrated that Aeromonas spp. can be associated with spoilage in vacuum packaged products such as pre-rigor filleted Atlantic salmon by the production of TMA, hypoxanthine, and H 2 S [ 30 ], and in cold smoked salmon by the production of TVBN [ 31 ]. Inoculation of A. salmonicida in shrimps under MA (50/50% CO 2 /N 2 ) resulted in the production of off-odours described as butter, sour, sulphur, and amine [ 32 ].…”