## 3 Results and Discussion
### Effect of HPP on Textural Properties  
Cheese texture is an important quality parameter that derives from the extensive chemical and biochemical changes that occur during ripening. Proteolysis is among the biochemical changes that may contribute to such textural properties. An evaluation of texture in Serra da Estrela cheese manufactured in different dairies was reported in [31]. The textural changes during the refrigerated storage of the control and HPP-treated _Serra da Estrela_ cheeses are shown in Table 2. Significant texture changes (\(p<0.05\)) were observed throughout refrigerated storage for all cheeses under analysis. However, HPP treatment did not significantly affect the hardness, consistency, adhesiveness, cohesiveness and gumminess of the cheeses at 0 months in comparison to the Ch\({}_{\text{C}}\) cheeses (\(p>0.05\)). Similarly, [PERSON] et al. (2007) [12] and [PERSON] et al. (2012) [25] noticed that HPP (400 MPa/10 min) applied to La Serena cheese at 50 days of ripening and HPP (400 or 600 MPa/7 min) applied to Ibores cheese (raw goat's milk) at 30 days of ripening had no significant effect on texture. However, a significant effect was observed after storage (10 days) of HPP-treated and non-treated ripened (50 days) cheeses [22]. Camembert cheese (pasteurized cow milk) HPP-treated (550 MPa/10 min) at 45 days of ripening revealed no significant effect on firmness [32]. Hardness (instrumental/sensorial) values express the maximum force needed to attain a given deformation or the force required to compress a cheese with the molars to the point of penetration, respectively [33]. As shown in Table 2, the P1 cheeses became harder and more consistent during the storage period (\(p<0.001\)), except for the samples measured after 15 months of storage. Such an increase may be related, on the one hand, with the progressively lower moisture contents reported up to 6 months of refrigerated storage. On the other hand, this variation in the textural properties of the P1 cheeses also revealed a positive correlation with the proteolysis levels previously discussed and with the sensorial analysis  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Property**} & **Storage Time** & \multicolumn{2}{c}{**P1**} & **P2** & **P3** \\  & **(Months)** & **Chc** & **600 MPa/6\({}^{\prime}\)** & **450 MPa/6\({}^{\prime}\)** & **450 MPa/9\({}^{\prime}\)** \\ \hline \multirow{4}{*}{Activity for Leu-\(p\)-Na *} & 0 & 11.0 \(\pm\) 0.8 \({}^{\text{a,A}}\) & 11.2 \(\pm\) 0.5 \({}^{\text{a,B}}\) & 10.4 \(\pm\) 0.8 \({}^{\text{a,A}}\) & 10.4 \(\pm\) 0.8 \({}^{\text{a,A}}\) \\  & 3 & 9.8 \(\pm\) 0.6 \({}^{  
described below; as previously discussed, a lower ripening extension index (less primary proteolysis) is related to a firmer cheese. [PERSON] et al. (2013) [PERSON] et al. (2013) reported an increase in hardness for ripened Ibores cheeses treated with HPP (600 MPa/7 min) and after storage for 90 days. The P2 cheeses maintained similar values of hardness and consistency throughout storage (\(p>0.05\)), with values closer to those of the \(\mathrm{Ch_{C}}\) cheeses at 0 months (upon 45 days of ripening), in line with what was observed and discussed for the proteolytic indexes. In general, the cohesiveness increased during the first 90 days of storage for all the cheeses but then showed no significant differences (\(p>0.05\)), except for the \(\mathrm{Ch_{C}}\) cheeses at 15 months storage, which revealed significantly lower values (\(p<0.001\)) than the HPP-treated cheeses. Cohesiveness (instrumental/sensorial) expresses the energy needed to be applied during mastication to break down the product until it is ready to be swallowed, representing the strength of internal bonds, or it measures the cohesion of the cheese mass throughout mastication, respectively [PERSON] et al. (2013).