## 3 Results and Discussion
### Microbial Growth during Refrigerated Storage  
The microbial load of TVC, _Pseudomonas_ spp., _Enterobacteriaceae_ spp., and LAB in MAP and ACT-MAP gutted sea bass stored at temperatures 0, 5, and 10 \({}^{\circ}\)C is depicted in Figures 3-6, respectively. The experimental data were fitted to the Baranyi growth model, and the respective kinetic parameters at each condition were determined, as presented in Table 1.  
The initial total viable count for the fresh gutted sea bass was approximately 4 log CFU g\({}^{-1}\) (Figure 3) [27]. The MAP and ACT-MAP gutted sea bass samples presented similar TVC growth curves. The ACT-MAP gutted sea bass samples reached the value of 7 log CFU g\({}^{-1}\) on days 22, 17, and 10 at 0, 5, and 10 \({}^{\circ}\)C, respectively. The MAP gutted sea bass samples reached the same log CFU g\({}^{-1}\) value quicker on days 18, 10, and 6 at 0, 5, and 10 \({}^{\circ}\)C, respectively. The significant inhibitory effect of CO\({}_{2}\) emitters was observed for the total viable microbial growth due to a lag phase increase in all the ACT-MAP samples (\(p<0.05\)) (e.g., 6.7 d for ACT-MAP samples compared to 1.8 d for the respective MAP samples stored at 5 \({}^{\circ}\)C; Table 1). The rates of TVC growth were also lower for the ACT-MAP samples compared  
Figure 2: O\({}_{2}\) concentration in the sea bass package headspace during the isothermal storage at (a) 0 \({}^{\circ}\)C, (b) 5 \({}^{\circ}\)C, and (c) 10 \({}^{\circ}\)C (grey bars ACT-MAP, black bars MAP). to the MAP samples (\(p<0.05\); apart from the ACT-MAP samples stored at the lowest temperature of 0 \({}^{\circ}\)C). [PERSON] et al. [19; 20; 21] measured the TVC of the MAP and MAP + CO\({}_{2}\) emitter packaged salmon fillets to be from 5 to 6 log CFU g\({}^{-1}\) after 15 days compared to the packaged under vacuum salmon samples that reached the same value after 7 to 10 days. It has been reported that MAP packaging with CO\({}_{2}\) enrichment is the most effective packaging technique for the microbial growth inhibition and shelf life extension of sea bass [28; 29]. More specifically, increasing the CO\({}_{2}\) and reducing the O\({}_{2}\), the aerobic bacteria and Gram-negative bacteria growth (e.g., _Pseudomonas_ spp., _Shewanella_ spp.) is delayed. Figure 3: Total viable count in MAP and ACT-MAP sea bass during the isothermal storage at (**a**) 0 \({}^{\circ}\)C, (**b**) 5 \({}^{\circ}\)C, and (**c**) 10 \({}^{\circ}\)C (\(\bigcirc\) ACT-MAP, \(\bigcirc\) MAP). The initial _Pseudomonas_ spp. has been reported to be between 2.5 and 3.9 log CFU g\({}^{-1}\) for sea bass [30; 31; 32]. In this study, at initial storage times, _Pseudomonas_ counts were also low (ranging from the initial value of 3.0 to the value of 4.0 log CFU g\({}^{-1}\)), reaching the value of 6.0 log CFU g\({}^{-1}\) (Figure 4). The _Pseudomonas_ spp. growth rates were significantly lower for ACT-MAP samples compared to MAP samples stored under the same time-temperature conditions (\(p<0.05\)). At a storage temperature of 0 \({}^{\circ}\)C, the decrease of the _Pseudomonas_ spp. growth rate (0.165 compared to 0.108 d\({}^{-1}\)) was accompanied by a lag phase increase (from 2 to 8 d), showing that the use of the CO\({}_{2}\) emitter led to a significant inhibition of _Pseudomonas_ spp. growth. _Enterobacteriaceae_ spp. and LAB have also been reported in sea bass fillets (smaller extent) [29]. In this study, the initial population of _Enterobacteriaceae_ spp. and LAB was low (Figure 5). _Enterobacteriaceae_ spp. and LAB was  
Figure 4: _Pseudomonas_ spp. count in MAP and ACT-MAP sea bass during the isothermal storage at (a) 0 \({}^{\circ}\)C, (b) 5 \({}^{\circ}\)C, and (c) 10 \({}^{\circ}\)C (\(\odot\) ACT-MAP, \(\bullet\) MAP). spp. presented increased growth rates under MAP with increasing storage temperatures from 0 \({}^{\circ}\)C to 10 \({}^{\circ}\)C for both MAP and ACT-MAP samples. ACT-MAP samples presented an _Enterobacteriaceae_ spp.