## 3 Results and Discussion
### pH of Pasteurized Orange Juice  
The following exponential 3P model describes the best-fit change in pH with the storage time via temperature as an accelerating factor (AICc = 418.2, R\({}^{2}\) = 0.554):  
\[Y=a+b*c^{*Days} \tag{2}\]  
where \(a\) is the asymptote, \(b\) is the scale, and c is the growth rate.  
Table 3 presents comparisons of the inflection points between different aging temperatures of the juice pH. This table highlights the decreasing trend of the pH along with the temperature increase based on the increasing growth rates, although this trend is more evident and statistically significant at higher temperature levels (20-25 \({}^{\circ}\)C) based on \(p\)-values. Furtherly, the progression of the pH is stable during the storage time at levels ranging between 3.9 and 4 until the 30 th day, regardless of the storage temperature (Figure 3). This trend was also observed in the work performed by [PERSON] et al. [21], where the pH of orange juice remained nearly stable during 24 days of storage at 4 and 25 \({}^{\circ}\)C, with values ranging from 4.45 to 4.23 and 4.31 to 4.29, respectively. Also, in the work performed by [PERSON] et al. (2008) [4], the pH of pasteurized orange juice remained stable for 6 weeks at 2 and 10 \({}^{\circ}\)C, with values ranging from 3.32 to 3.49 and 3.32 to 3.48, respectively. In our study, from the 30 th to the 40 th day of storage, the pH values declined progressively, with greater  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Temperature** & **Days** & **APC (Cfu/mL)** & \(-\)**95\%** & **95\%** \\ \hline
4 & 48.31 & 1000.4 & 109.1 & 9175.5 \\
5 & 37.11 & 1001.5 & 109.2 & 9186.3 \\
6 & 30.03 & - & - & - \\
10 & 16.35 & 1002.6 & 109.3 & 9195.8 \\
15 & 10.12 & 1001.4 & 109.2 & 9185.3 \\
20 & 7.2 & 1000.1 & 109 & 9173.2 \\
25 & 5.53 & 1000.3 & 109.1 & 9174.8 \\
30 & 4.46 & 1001.4 & 109.2 & 9184.6 \\
40 & 3.17 & 1000.7 & 109.1 & 9178.7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Shelf life of pasteurized orange juice at different temperature levels.  
Figure 2: Degradation profiler of APC versus period (days) and temperature level using a polynomial model.  
intensity for the samples with a higher storage temperature. More specifically, regarding samples preserved at 25 \({}^{\circ}\)C, a steep decrease in the pH from 3.8 to 3.4 was observed from the 30 th to the 40 th day (Figure 3), which is also illustrated by the value of the specific growth rate, i.e., 0.31, compared to the growth rates of 4 \({}^{\circ}\)C and 15 \({}^{\circ}\)C, which were 0.18 and \(-\)0.09, respectively (Table 3). This trend could be attributed to the rapid metabolization of the orange juice simple carbohydrates by the large numbers of aerobic plate counts at prolonged storage periods and higher temperatures, leading to the accumulation of organic acids as by-products of the reaction, subsequently lowering the pH values [21; 22]. Under normal conditions, in a pasteurized product, the bacteria that ferment sugars into organic acids are heat-sensitive and are destroyed, but the spore-forming strains of the _Alicyclobacillus_ genera and, more specifically, _Alicyclobacillus acidoterstris_, survive pasteurization and, after germination in ideal conditions, they cause acidification of the juice [23].