## 3 Results and Discussion
### Microbiological Analyses  
The microbial population present in fresh meat at the time of packaging is extremely varied and depends on the hygienic characteristics of the previous processing phases [31]. In our study, all samples were negative for coagulse positive staphylococci, _Listeria monocytogenes_, and _Salmonella_ spp., and the initial microbial loads ranged from \(2.5\pm 0.2\) Log CFU/g for _Lactobacillus_ spp. to \(3.6\pm 0.1\) Log CFU/g for the total viable count. After 6 days, a significant effect of storage time was found for all microorganisms evaluated, with an increase in overall bacterial counts over time (\(p<0.01\)). In fact, all bacteria had concentrations greater than 4 Log, with the exception of Lactobacillus (\(2.8\pm 0.1\) Log CFU/g). During storage, both temperature and packaging type are able to exercise selective pressure--with different consequences--on the bacterial replication rate and, therefore, on the related growth curves, regardless of the type of meat [33; 34; 35]. For example, in aerobic conditions, spoilage bacteria are mainly represented by _Pseudomonas_ spp. [36], while in the absence of oxygen, facultative anaerobic bacteria such as lactic acid bacteria and _Brochotrix thermosphacta_ are predominant [37]. In the current work, with the same oxygen and refrigeration conditions, the packaging influenced the growth trend and all bacteria showed a significant effect in response to the group and/or of the group--time interaction (\(p<0.05\)). In particular, after 3 days of storage, the control group showed higher concentrations in total viable count (\(+0.4\pm 0.1\) Log CFU/g; \(p=0.003\); Figure 3C), _Lactobacillus_ spp. (\(+0.2\pm 0.1\) Log CFU/g; \(p=0.028\); Figure 3A), _Lactococcus_ spp. (\(+0.3\pm 0.1\) Log CFU/g; \(p=0.014\); Figure 3B), _Enterobacteriaceae_ (\(+0.5\pm 0.1\) Log CFU/g; \(p<0.001\); Figure 3D), total coliforms (\(+0.5\pm 0.1\) Log CFU/g; \(p<0.001\); Figure 3E), _Pseudomonas_ spp. (\(+0.5\pm 0.1\) Log CFU/g; \(p<0.002\); Figure 3F), and _Brochotrix thermosphacta_ (\(+0.4\pm 0.1\) Log CFU/g; \(p=0.002\); Figure 3G) than the PAD group. At the end of the storage period (D6), all microbial counts, except for TVC and _Brochotrix thermosphacta_, continued to be lower in the PAD group, but these differences were no longer significant. Therefore, the antimicrobial effect exerted by the active pad seems to have been exhausted in the second part of storage, allowing all microorganisms to reach similar counts as the control group at day 6. It is possible that the capturing action of the pad, which is physical-mechanical and not bactericidal, may have been effective only up to a certain microbial load, beyond which the bacteria were released again on the meat surface. However, analyzing in percentage terms, the differences in concentrations detected at day 3, the growth rate of total coliform, _Enterobacteriaceae_, _Pseudomonas_ spp. and _Brocottrix thermosphacta_ was influenced more by the active pad, with count reductions of 20.2%, 18.4%, 16.8% and 16.1%, respectively, while TVC, Lactobacillus and Lactococci were less affected (reduction of 11%, 10% and 8.2%, respectively). This different growth trend under the same conservation conditions could be relevant, considering that only a fraction of the initial microbial population is effectively involved in the deterioration process [37]. In particular, _Brocottrix thermosphacta_ and _Pseudomonas_ spp. are recognized to be spoilage related. Previous studies have shown that some members of the _Pseudomonas_ family, \begin{table}
\begin{tabular}{c c c c} \hline  & \multicolumn{3}{c}{**Storage Time**} \\ \cline{2-4}  & **Day 0** & **Control vs. PAD Day 3** & **Control vs. PAD Day 6** \\ \hline  & & 1.69 & 5.35 * \\ \hline  & D0–D3 & D3–D6 & D0–D6 \\ \hline Control & 1.41 & 9.34 * & 9.88 * \\ PAD & 1.96 & 4.05 * & 5.73 * \\ \hline \end{tabular}  
* Value over the threshold (2.3 points) with a noticeable difference in color between the samples.  
\end{table}