## 3 Results and Discussion
### The Results of Microbiological Analyses  
Fish is a commodity with a very short shelf life. Among others, its overall quality is influenced by storage temperature, packaging, and the initial quality of the raw material. The results of microbiological analyses of vacuum-packed fresh burgers are shown in  
Figure 6: Total mesophilic microbial counts (**a**), psychrophilic microbial counts (**b**), Enterobacteriaceaeaceae (**c**), _Pseudomonas_ sp. (**d**), and lactic acid bacteria (**e**) counts expressed in log CFU/g of fish burgers during 13 days of storage. CON—burger without extracts; JB—burger with 2% of 1:2 common juniper by-product/blackberry leaves extract; PCJ—burger with 2% of 1:1 _Padina paroonia_/prickly juniper needles extract; BCV—burger with 2% of 2:1:1 blackberry leaves extract/catechin/vanillic acid. Figure 6a-e. The initial TVC number reported for sea bass or hake is usually higher in the range of 3-4 log CFU/g [39; 55; 56]. The MEZ counts increased from 2.03 to 4.65 log CFU/g in the control burger. The initial MEZ count was lower in fish burgers with extracts; however, the count increased in all fish burgers throughout the storage. The lowest MEZ count at the end of the storage period was recorded for the JB burger (4.32 log CFU/g), followed by the BCV burger (4.49 log CFU/g). The PSI counts increased from 1.99 to 4.71 log CFU/g in the control burger during the 13 days (Figure 6a). All burgers with extracts had lower PSI microbial counts on the first day of storage, with 1.76 log CFU/g for JB, 1.79 log CFU/g for PCJ, and 1.91 log CFU/g for BCV. Total PSI counts increased with storage time in all fish burgers; however, JB and BCV burgers had lower PSI counts than the control burger at the end of the storage period (Figure 6b). Furthermore, the highest initial count of Enterobacteriaceae was found in the control burger (1.44 log CFU/g). Fish burgers with extracts had lower initial Enterobacteriaceae cause counts but slightly higher counts at the end of the storage period (Figure 6c). The counts of LAB differed significantly. Over the storage period, the LAB count was the highest in the PCJ burger, reaching 4.07 log CFU/g at the end (Figure 6d). Pseudomonas sp. counts increased from 1.87 to 4.88 log CFU/g in the control burger during the 19 days of shelf life in refrigerated conditions. All fish burgers with extracts had lower initial and final Pseudomonas sp. counts, with the lowest final count of 4.09 log CFU/g recorded for the JB burger (Figure 6e). Microbiological standards and guidelines accept a total aerobic psychotropic count of 6 log CFU/g for chilled fish as acceptable quality for human consumption, while at microbial loads of 7-8 log CFU/g, the spoilage can be detected organoleptically [57; 58]. Testing the effect of the plant extract mixtures (blackberry, juniper, _Padina pavonica_) alone and with pure compounds to evaluate their effects against microbial counts in fish products is limited to one previously published report. Previously studied extracts have been proven to be effective against Gram-positive pathogens, _Pseudomonas_ and _Shewanella_ spp. [16; 27], and these results were tested in a study on sea bass fillets under MAP. _Padina pavonica_ extract (alone or in combination) suppressed the bacterial growth, contributing to a shelf-life prolongation of the product [16]. Juniperus essential oil (0.3-0.6%) significantly inhibited total mesophilic bacteria count in vacuum-packed rainbow trout fillets stored at 2 \(\pm\) 1 \({}^{\circ}\)C. The threshold of 7 log CFU/g was reached after 19 days in the control samples, and after 25 and 31 days in 0.3 and 0.6% juniper essential oil samples, respectively [46]. Rosemary was found to be effective in reducing microbial growth in sea bass fillets during storage at 4 \({}^{\circ}\)C and in extending the shelf life from 20 to 29 days [55]. [PERSON] et al. [39] found that combined effect of plant-based extracts of blueberry and seaweeds, together with LAB supernatant, can increase the microbiological stability of modified packed sea bass fillets.