## 3 Results and Discussions
### Microbiological Analysis
#### 3.2.1 Aerobic Plate Count (APC)
All three cooking systems that involved convection had an average APC of 3.69 log CFU/g, still below the accepted maximum. In the cook-chill system, this level showed some fluctuations, decreasing by 0.02 log CFU/g after the first day and then increasing slightly until day four. Between day four and day five, a new decrease of another 0.02 log CFU/g was recorded. Over the 5 days of sample testing of the cook-chill system, the APC increased by a total of 0.06 log CFU/g. In the cook-freeze system, the APC level decreased by a total of 0.08 log CFU/g until day 30, after which it increased by a total of 0.09 log CFU/g. Thus, in the fish dish made in the cook-serve system, the APC decreased by 61%, in the cook-chill sample, it decreased by 44%, and in the cook-freeze sample, it decreased by 52%. Unconventional heat treatment using microwaves proved to be more effective in reducing the microbial load. Thus, the APC in sample A3 was 2.99 log CFU/g, 10.5 times lower than the non-heat-treated product and 4 times lower than the conventional heat-treated product. All APC values are presented in Figure 1 as log CFU/g. The production of the fish dish in the cook-chill system (CC-CC, convective oven followed by rapid cooling in two stages to the refrigeration temperature) resulted in a 45% higher level of bacterial contamination than in the product prepared in the cook-serve system. Products made in the cook-freeze system (CC-CF, convective oven followed by rapid cooling in two stages to freezing temperature) presented a 24.2% higher load compared to that of the same product made in the cook-serve system. Other studies have reported similar APCs below the European Commission Regulation limits, such as of 4 log CFU/g (sardines [64]), 3.9 log CFU/g (red porgy [65]), 3.46 log CFU/g (bonito [66]), 3.70 log CFU/g (_Dicentrarchus labrax_, [67]), and 3.53 log CFU/g (carp fillets [68]), while some others had considerably lower levels (2.9 log CFU/g in eel [69]). [PERSON] et al. [70] also analyzed four different fish species, with salmon being one of them, and obtained minimal results in the microbial loads, with the APCs under 1 log CFU/g. _E. coli_, _S. aureus_, _Salmonella_ sp., _L. monocytogenes_, and _C. perfringens_ were not detected in their samples. APCs that exceed the European Commission Regulation limits  
Figure 1: Total aerobic mesophilic bacterial count (log10 CFU/g) in the different catering fish dishes cooked using different techniques (A0—control; A1—sous vide cook-serve; A2—convection cook–serve; A3—microwave cook-serve; A4—convection cook–hill; A5—convection cook–freeze). The results are expressed as the mean value of the three replicates \(\pm\) the standard deviation (SD); different letters indicate significant differences (Tukey’s test, \(p\leq 0.05\)). have been reported by [PERSON] et al. [71] (4.5 log CFU/g in sous vide cooked salmon fillets), [PERSON] et al. [72] (6.08 log CFU/g in sardines), and [PERSON] et al. [73] (9.14 log CFU/g also in sardines). The microbiological stability of catering products was monitored during the shelf life provided by the product standard in terms of the evolution of the aerobic mesophilic microorganisms' content. The shelf life is estimated at 5 days for dishes prepared in the cook-chill system (CC-CC), stored at a temperature of 4 \({}^{\circ}\)C, and 50 days for dishes prepared in the cook-freeze system (CC-CF), stored at a temperature of \(-\)18 \({}^{\circ}\)C. Following the microbiological analysis of the sample stored for 5 (A4-e) and 50 days (A5-e), respectively, it was possible to assume and declare the shelf life of the catering products. Samples were taken and analyzed from the refrigerated products coded A4a-e every day of the shelf life.