## 3 Results  
### Physicochemical Analysis  
1.1 Effects of the Three Tested Plant Powders on the pH and Water Activity (a\({}_{\mathrm{w}}\)) Values of the Mortadellas  
The mean values and standard deviations of the pH and water activity (a\({}_{\mathrm{w}}\)) of the three experimental mortadella formulations (MTS1 (containing mandarin peel powder), MTS2 (containing common lambsquarter powder), and MTS3 (containing oregano powder)) and the control one (MTC) are shown in Figures 2 and 3. Further statistical information is reported in the supplementary materials (Table S1).  
From day 1 to day 30, corresponding to the beginning and the end of the evaluation period, pH trends were non-linear across all the samples (Figure 2). Notably, MTS1 and MTS3 showed similar trends, with pH values initially increasing, then decreasing, and subsequently rising again. In meat and meat products, an increase in pH values during aging could be attributed to the hydrolysis of meat proteins to amino acids [42]. A similar trend was reported by [PERSON] et al. [43], who conducted a study comparable to ours, comparing mortadella formulated with synthetic antioxidants to that made of curcumin microcrystals in relation to their physicochemical and sensory characteristics. Conversely, the pH values of MTS2 showed a decrease at 15 days of storage, probably attributed to the antimicrobial activity of the extract [30], followed by an increase from day 15 to day 30. Although at the end of the evaluation period (T3), all the samples showed higher values compared to those recorded at T0, according to [PERSON] et al. [44], the observed pH levels are still considered as ideal to guarantee the microbiological and structural stability of emulsified products. Furthermore, these values have also contributed to the color stability of the mortadellas, especially the redness values (Table 1). Similar findings were obtained by [PERSON] et al. [45], in which mortadella formulations were prepared by adding mango seed extract, and slight increases in pH values were observed, rising from 5.91 \(\pm\) 0.01 (at day 0) to 6.06 \(\pm\) 0.02 at the end of a 21-day storage period. Our results align with the findings of [PERSON] et al. [43], who incorporated curcumin into mortadella formulations. In their study, a pH value of 6.10 was recorded after 30 days of storage. The pH variations of the three experimental mortadella samples were compared to those of the control sample from day 1 to day 30, highlighting that the trends for MTS1 and MTS3 deviated from that observed in the control.  
Regarding the water activity (a\({}_{\mathrm{w}}\)), this is a critical parameter of cooked meat products, as high values promote the development of undesirable microorganisms, while low values negatively impact the texture and flavor [44]. From Figure 3, it is evident that the obtained a\({}_{\mathrm{v}}\) values remained consistently around 0.95-0.96 across all the samples (MTS1, MTS2, MTS3, and MTC), indicating that this parameter was well controlled by the natural powders. Notably, slight increases in a\({}_{\mathrm{w}}\) were observed at 15 days of the storage period in all the samples, followed by slight decreases at 30 days of storage (Figure 3). These results agree with the findings of [PERSON] et al. [46], who reported similar trends in mortadella formulations stored at 14 \({}^{\circ}\)C.  
Figure 3: Trends of a\({}_{\mathrm{w}}\) values in the four mortadella formulations during the storage period. MTS1 = mandarin peel, MTS2 = common lambsquarters, MTS3 = oregano, and MTC = sodium nitrite.  
Figure 2: Trends of pH values in the four mortadella formulations during the storage period. MTS1 = mandarin peel, MTS2 = common lambsquarters, MTS3 = oregano, and MTC = sodium nitrite.