## 3 Results and Discussion
acidoterrestris_ in BAM broth when treated at 350 and 450 MPa combined with different temperatures (35, 45, and 50 \({}^{\circ}\)C) [35]. Moreover, apart from HHP treatment, the Weibull model could effectively describe the inactivation of _A. acidoterrestris_ vegetative cells and spores by other emerging technologies such as ultrasound [21], UV-C light irradiation [44] and pulsed light [22]. An increase trend in the shape factor (\(p\)) with the HHP treatment was observed at all temperatures assayed with the exception of 600 MPa for strain B where a decrease in the values of \(p\) was evident with increasing temperature level (Table 1; Figure 3). This trend in shape factor values is in agreement with previous researchers [35; 45] who reported that the shape parameter was dependent on temperature at certain pressures. However, other reports noted that the shape factor indicates the kinetic pattern that describes the inactivation process and thus it should be independent of the external factor \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Strain A** & **T 1 (\({}^{\circ}\)C)** & \(\delta\) 2 (min)** & \(p\)3 ** & **RMSE 4** & **R2 5** \\ \hline  & 45 & 0.039 & 0.176 & 0.517 & 0.769 \\
500 MPa & 60 & 0.013 & 0.218 & 0.496 & 0.940 \\  & 70 & 0.020 & 0.258 & 0.249 & 0.985 \\ \hline  & 45 & 0.009 & 0.153 & 0.251 & 0.944 \\
600 MPa & 60 & 0.007 & 0.222 & 0.185 & 0.991 \\  & 70 & 0.004 & 0.286 & 0.407 & 0.962 \\ \hline
**Strain B** & **T (\({}^{\circ}\)C)** & \(\delta\) **(min)** & \(p\) & **RMSE** & **R2** \\ \hline  & 45 & 0.492 & 0.225 & 0.320 & 0.844 \\
500 MPa & 60 & 0.104 & 0.293 & 0.323 & 0.961 \\  & 70 & 0.027 & 0.264 & 0.200 & 0.990 \\ \hline  & 45 & 2.493 & 0.318 & 0.172 & 0.407 \\
600 MPa & 60 & 0.040 & 0.248 & 0.544 & 0.894 \\  & 70 & 0.007 & 0.235 & 0.538 & 0.981 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: [PERSON] model-estimated kinetic parameters and goodness-of-fit indices for the inactivation of _A. acidoterrestris_ spores for Strains A and B using temperature-assisted high-pressure processing. (i.e., temperature) [5; 46], whereas [PERSON] [38] reported that in only 7 out of 55 studies the shape factor seemed to be dependent from temperature. The scale parameter \(\delta\) in this model equals the first decimal reduction time (1D, min) that results in 1-log CFU/mL reduction of the surviving spores' population and could be used as an indication of how rapidly the spores are inactivated [47]. Based on the estimated values of this parameter (\(\delta\)), the longest spore survival in orange juice was observed for the reference strain B at 600 MPa/45 \({}^{\circ}\)C, whereas the wild-type strain A presented lower survival at the same temperature (Figure 4). The differences for the 1-log CFU/mL reduction in the surviving population of spores between the two strains were practically diminished as processing temperature increased. It could thus be suggested that at the selected high pressure levels, the temperature should be higher than 60 \({}^{\circ}\)C for effective spore inactivation. Regarding the scale parameter (\(\delta\)), a decrease of log(\(\delta\)) with temperature was noted at all high pressure levels applied (Figure 3). The data points were fitted with a linear function as shown in Figure 3 providing information on the temperature sensitivity of \(\delta\) values for a given high pressure level. Thus, for the wild strain A the \(z\) values were 76 and 74 \({}^{\circ}\)C for HPP treatment at 500 and 600 MPa, respectively, indicating that temperature changes have minor effect on \(\delta\) values for this strain. However, the respective \(z\) values for strain B were 20 and 10 \({}^{\circ}\)C for the same pressurization levels, indicating a larger effect of temperature changes on \(\delta\) values for this strain of the bacterium. The results obtained in this work for the \(z\) values of the reference strain B are comparable with previous researchers [5] who reported \(z\) values between 20.07 and 21.43 \({}^{\circ}\)C for _A.