## 3 Results and Discussion  
During meat processing, the pH value is linked to several processes such as protein denaturizing and gelation, enzymatic activities and chemical reactions such as the Maillard reaction or non-enzymatic browning. Its control during processing is therefore necessary to produce safe, high-quality and value-added products [32]. As shown in Figure 2A, pH values were greater in the SN (6.20 \(\pm\) 0.03) and NM (6.20 \(\pm\) 0.03) groups compared to the CON (6.14 \(\pm\) 0.03) and POL (6.15 \(\pm\) 0.03) groups on day 0 (\(p\) < 0.05). The SN and NM groups also had greater pH values at months 1, 2 and 3, with the greater difference observed during the last sampling day (6.23 \(\pm\) 0.03 and 6.14 \(\pm\) 0.03 versus 5.94 \(\pm\) 0.03, 5.92 \(\pm\) 0.03 and 5.85 \(\pm\) 0.03 for the SN, NM, CON, POL and NM + POL groups, respectively (\(p\) < 0.05). The replacement of nitrate/nitrite with an olive leaf extract containing oleuppen at 93 mg/kg in ripened pork sausages resulted in a decrease in the pH values [33], as indicated in the present study. In another study, olive leaf extract had no effect on the pH of pork sausages compared with a control sample [34]. [PERSON] et al. [35] observed a decrease in the pork sausages' pH values after applying phenols (75-150 mg/100 g of dough) extracted from an oil mill by-product. No effect of hot-water lemon balm ethanol extract (10%) on the pH values in beef patties was observed by [PERSON] et al. [36]. However, pH values were decreased as an effect of the addition of lemon balm powder (total polyphenol content of 800 mg on dry matter basis) at 1% in hamburger patties [37]. A decrease in the pH value was also evident as an effect of rosemary addition (total phenolic content of 31.36 mg gallic acid equivalent--GAE--on dry matter basis) in western-style smoked sausages [38]. The pH was significantly decreased in pork sausages following the addition of thyme and rosemary powder at 0.1-0.2 [39]. Moreover, the pH levels in the five experimental groups were greater at month 2 compared to month 0 and month 1; this fact could be ascribed to the generation of proteases by psychrotrophic bacteria [40]. Finally, a reduction in the pH values was observed in the treatment groups at month 3, possibly as a result of lactic acid bacterial development [41]. Values for cooking loss and tenderness were not significantly influenced by the addition of natural polyphenols and/or an herbal mix (Figure 2B,C). Cooking loss has a great impact on sensory quality attributes such as juiciness and tenderness [42]. The texture of meat products is an important quality trait strongly associated with sensory perception and consumer acceptance [32]. Shear force value was therefore evaluated in the present study to identify any possible side effects following the addition of the polyphenols and/or herbal mix to the sausages that might induce a negative eating experience for the consumer [43]. To our knowledge, few studies have been performed to evaluate texture parameters in meat products after polyphenol supplementation. As indicated, phenolic compounds can contribute to the structural alteration and partial fragmentation of myofibril proteins, which could lead to an improvement in meat tenderness [44]. However, when the total polyphenol content is increased, the number of hydroxyl groups and their interaction with myofibril proteins are also enhanced resulting in the aggregation of proteins. As a result, a more compact meat structure is observed and the water from the myofibrils is expelled, leading to impaired tenderness [44]. In accordance with our results, previous researchers also observed no significant effect of the addition of olive leaf extract on the pH, cooking losses and tenderness of beef patties [45] and pork sausages [34]. The maximum compression force (N) during texture analysis was not affected by a green tea extract addition (500 mg/kg) in frankfurter-type sausages, while the incorporation of olive leaves' extract (500 mg/kg) increased this value [46].