## 3 Results and Discussion  
### Physico-Chemical Parameters  
The TVBN values increased in all samples (\(p<0.001\)) but with significant differences between groups at all storage times. Indeed, the pad showed lower values than the control both after 3 (\(16.8\pm 0.1\) and \(16.4\) mg/100 g \(\pm\) 0.1 for C and PAD group, respectively; \(p\) = 0.036) and 6 days (\(19.2\pm 0.1\) and \(18.1\) mg/100 g \(\pm\) 0.1 for C and PAD group, respectively; \(p<0.001\)) of storage. Overall, the initial pH (\(5.54\pm 0.01\)) decreased after 3 days (\(5.46\pm 0.01\)) and then increased until \(5.57\pm 0.01\) after 6 days of storage (\(p<0.001\)). At day 3, the pad had higher values compared to the control group (\(p=0.004\)) but the differences were no longer significant after 6 days of storage (\(p=0.354\); Table 1). During the storage of fresh meat, the pH generally follows a similar trend, with values that tend to increase as the shelf life progresses. This is associated with the presence of nitrogen compounds that are generated during storage following the degradation of proteins by certain microbial species, in particular Gram-negative bacteria [25]. In our study, however, we observed an initial pH reduction (day 3) in the control group, which could be explained by a slight acidification induced by lactic acid bacteria. These microorganisms are normally present on meat and their metabolism leads to lactic acid production [26]. Therefore, if the ratio between basic compounds and acids is in favor of the latter, the pH will tend to decrease. This analysis is consistent with the microbial counts detected, where at day 3, Lactobacillus and Lactococci had higher concentrations in the control samples than in the meat packaged with active pad (Figure 3A,B). The color parameters L*, a*, and b* reduced over time in both groups (\(p<0.001\)) but significant differences between groups were found only for L*. In particular, pad samples showed higher L* values than the control at day 6 of storage (\(p<0.001\); Table 1). Color alteration is one of the aspects that limits the preservation of meat the most, as well as conditioning the consumer's preference at the time of purchase [27; 28]. It is therefore essential that during retail display, the color deteriorates as little as possible. Color changes are mainly related to the oxidation of the protein (transformation of red oximioglobin to brown methyloglobin) and lipid components and the two processes are closely correlated [29]. For these reasons, the meat industry \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Day**} & \multicolumn{2}{c}{**Group**} & \multicolumn{3}{c}{**Significance**} \\  & & **Control** & **PAD** & **Group** & **Time** & **Group \(\times\) Time** \\ \hline \multirow{3}{*}{**pH**} & **0** & \multicolumn{3}{c}{\(5.54\pm 0.01\)} & \multirow{3}{*}{0.008} & \multirow{3}{*}{\(<\)0.001} \\  & **3** & \(5.42\pm 0.02\) & \(5.49\pm 0.02\) & & \\  & **6** & \(5.56\pm 0.02\) & \(5.58\pm 0.02\) & & \\ \hline \multirow{3}{*}{**L*} & **0** & \multicolumn{3}{c}{\(45.90\pm 0.24\)} & \multirow{3}{*}{\(<\)0.001} & \multirow{3}{*}{\(<\)0.001} & \multirow{3}{*}{\(<\)0.001} \\  & **3** & \(45.22\pm 0.25\) & \(45.04\pm 0.25\) & & \\  & **6** & \(36.83\pm 0.25\) & \(42.15\pm 0.25\) & & \\ \hline \multirow{3}{*}{**a*} & **0** & \multicolumn{3}{c}{\(22.43\pm 0.07\)} & \multirow{3}{*}{0.562} & \multirow{3}{*}{\(<\)0.001} & \multirow{3}{*}{0.087} \\  & **3** & \(21.40\pm 0.15\) & \(22.23\pm 0.15\) & & \\ \cline{1-1}  & **6** & \(19.86\pm 0.71\) & \(19.44\pm 0.27\) & & \\ \hline \multirow{3}{*}{**b*} & **0** & \multicolumn{3}{c}{\(14.54\pm 0.10\)} & \multirow{3}{*}{0.198} & \multirow{3}{*}{\(<\)0.001} & \multirow{3}{*}{0.908} \\  & **3** & \(13.58\pm 0.09\) & \(13.33\pm 0.07\) & & \\ \cline{1-1}  & **6** & \(11.62\pm 0.35\) & \(11.41\pm 0.08\) & & \\ \hline \hline \end{tabular} Values at time 0 were included in each model as covariate. Values followed by the same letter in each row do not differ significantly (\(p<0.05\)).  
\end{table}