## 3 Results and Discussion
### Shelf Life Estimation
More recently, [PERSON] et al. [21] showed that vacuum + -CO\({}_{2}\) emitter packaged cod fillets displayed 2 days of shelf life extension compared to vacuum-packed samples. The maximum shelf life (13 d) was reported for the MAP (60% CO\({}_{2}\)-40% N\({}_{2}\)) and CO\({}_{2}\) emitters. In the present study, the incorporation of CO\({}_{2}\) emitters in the MAP of gutted sea bass has been investigated as a potential tool to maintain fish quality and further extend shelf life. The tested CO\({}_{2}\) emitters, prepared by NaHCO\({}_{3}\) and citric acid, produce CO\({}_{2}\) gas in contact with water that is obtained from liquid leaking from the fish flesh and thereby compensate for the reduced gas volume to product volume ratio. Thus, such CO\({}_{2}\) emitters may also simultaneously act as liquid absorbers [1]. In any case, CO\({}_{2}\) generators are used in the active packaging system for the purpose of increasing the lag phase and inhibiting the growth of bacteria in certain food products. Similar CO\({}_{2}\) pads have also been reported to sufficiently reduce the transport volume of MAP-farmed cod and Atlantic salmon [19; 20]. Different types of CO\({}_{2}\) emitters have also been developed, which utilize the O\({}_{2}\) from the package atmosphere to form CO\({}_{2}\) and develop a CO\({}_{2}\)/N\({}_{2}\) headspace into the package without implicating any gas insertion. Alternative techniques to generate CO\({}_{2}\) into the food package after sealing include the utilization of dry ice or carbonate in some cases in combination with weak acids [22; 37]. It has been reported that the effect of CO\({}_{2}\) varies upon microorganisms. For example, moderate to high CO\({}_{2}\) concentrations (10-20%) can slow down the growth of aerobic bacteria, while the growth of LAB is stimulated by CO\({}_{2}\)[38]. Commercially available CO\({}_{2}\) emitters in many cases include ferrous carbonate and a metal halide catalyst to absorb O\({}_{2}\) and produce equal volumes of CO\({}_{2}\)[39; 40]. The present article demonstrates the investigation of the effect of a CO\({}_{2}\) emitter-assisted MAP type as an effective active packaging system to prolong the shelf life of gutted sea bass in the cold chain. This study has been implemented at isothermal storage conditions in the range of 0-10 \({}^{\circ}\)C. Effective mathematical models must be validated at variable conditions, simulated time-temperature scenarios of the actual cold chain, and on independent fish batches. Additionally, since high concentrations of CO\({}_{2}\) are enabled, particular care should be taken in determining the safety of packed fish, especially when processing significantly extends the shelf life, such as for example high pressure [41; 42; 43]. For this \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **Shelf Life (d)** & \\ \hline Storage temperature & 0 \({}^{\circ}\)C & 5 \({}^{\circ}\)C & 10 \({}^{\circ}\)C \\ \hline MAP & 18 & 10 & 6 \\ \hline ACT-MAP & 22 & 17 & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Shelf life of MAP and ACT-MAP gutted sea bass during the isothermal storage at 0 \({}^{\circ}\)C, 5 \({}^{\circ}\)C, and 10 \({}^{\circ}\)C by using the developed mathematical model (limit for shelf life estimation = 10\({}^{7}\) CFU g\({}^{-1}\) for the total viable count). reason, the U.S. Food and Drug Administration (FDA) Seafood Hazard Analysis Critical Control. Points (HACCP) guidelines (Chapter 13) suggest a minimum oxygen transmission rate in the final package of fish of at least 10,000 cc/m\({}^{2}\)/24 h at 24 \({}^{\circ}\)C to provide sufficient oxygen that allows growth of aerobic spoilage organisms before _Clostridium botulinum_ toxin formation under moderate abuse temperatures, thus limiting the innovation and application of new packaging methods in the fish industry sector [44]. Future research should be focused on initiating hurdle technologies for optimum active packaging systems by incorporating multiple active components or active and smart functionalities in one system [38; 45; 46].