## 3 Results and Discussion
### Estimation of Microbial Growth Parameters and Shelf Life
#### 3.2.2 Microbial Growth Curves of HPP Samples  
In Figures 8a-d and 9a-d, the growth of TVCs and lactic acid bacteria in the HPP samples during storage at 4, 8, 12, and 18 \({}^{\circ}\)C is depicted, respectively. The results show that the predominant spoilage microorganisms were lactic acid bacteria for the HPP samples stored at all temperatures studied. Regarding _Brochotlrix thermosphacta_, its population remained below the detection limit (<2 log CFU/g) in the HPP frankfurter-type sausages during storage at all temperatures examined in this study. This growth can be attributed to the low redox potential (anaerobic environment) created due to vacuum and skin packaging, which inhibits aerobic microorganisms and favors the growth of lactic acid bacteria. The results of the microbiological analysis indicate that growth of the total viable count (TVC) and lactic acid bacteria increased with an increase in the storage temperature and time, following a similar profile to the CNT sausages. The initial TVC for the HPP sausage samples was below the detection limit <2.00 log CFU/g (Figure 8), showing that the initial microbiological quality of all frankfurter-type sausages was superior. It was observed that the numbers increased with an increase in both storage temperature and storage time, reaching 8.40-8.80 log CFU/g on the last day of storage at 4, 8, 12, and 18 \({}^{\circ}\)C. The longer frankfurter sausages were stored, the more the growth of microorganisms increased due to there being sufficient time for microbial multiplication. For frankfurters, the limit of acceptability in terms of the TVC (8 log CFU/g) for the HPP samples was reached after 89, 41, 11 and 7 days of storage at 4, 8, 12, and 18 \({}^{\circ}\)C, respectively. High-pressure processing (HPP)-cold pasteurization was observed to disrupt the microbial outer membrane, impacting both its structure and function [19]. The details of the mechanism by which HPP disrupts microbial cell membranes, leading to reduced microbial viability in meat products, have also been described by [PERSON] et al. [57]. Previous research has documented HPP as a highly effective \"cold\" sterilization technology that is widely used \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Storage Temperature (\({}^{\circ}\)C)** & \begin{tabular}{c} **Growth Rate** \\ **k (d\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Lag Phase** \\ **(d)** \\ \end{tabular} & \
\begin{tabular}{c} **R\({}^{2}\)** \\ **T\({}_{d}\) (d)** \\ \end{tabular} &
\begin{tabular}{c} **Doubling Time** \\ **T\({}_{d}\) (d)** \\ \end{tabular} \\ \hline
4 & 0.384 \(\pm\) 0.041 b & 8.27 \(\pm\) 0.87 a & 0.984 & 1.8 \\
8 & 0.465 \(\pm\) 0.063 c & 2.15 \(\pm\) 0.42 c & 0.971 & 1.4 \\
12 & 0.521 \(\pm\) 0.081 d & N.D. & 0.924 & 1.3 \\
18 & 1.132 \(\pm\) 0.301 e & N.D. & 0.947 & 0.6 \\ \hline VARI (T\({}_{\text{eff}}\) = 3.8 \({}^{\circ}\)C) & 0.267 \(\pm\) 0.032 a & 5.34 \(\pm\) 1.57 b & 0.979 & 2.6 \\ VAR2 (T\({}_{\text{eff}}\) = 9.7 \({}^{\circ}\)C) & 0.853 \(\pm\) 0.147 e & 2.05 \(\pm\) 0.84 c & 0.981 & 0.8 \\ \hline \hline \end{tabular}  
* N.D.: not detected. Different letters among lines indicate significant differences between means (\(\pm\)standard deviation) according to the mean values of [PERSON]’s post hoc comparison test for a significance level of \(p=0.05\).  
\end{table} 
Table 1: Kinetic parameters of the TVC growth in frankfurter-type sausages before HPP (reference samples (CNT)) at different isothermal and dynamic storage conditions. to improve microbiological safety and extend the shelf life of both pre- and post-packaged meat products [58]. The LAB behavior in response to HPP during storage at 4, 8, 12, and 18 \({}^{\circ}\)C has rarely been investigated. The initial LAB counts in all the groups were not detected (<1 log CFU/g; Figure 9). Similar growth to that of the TVC was also observed for the LAB on the HPP samples. As the storage time increased, the LAB counts in the HPP sausages became significantly lower (\(p\) < 0.05) than those in the CNT group.