## 3 Results and Discussion
### Quality of High Pressure Treated-Desalted Cod
#### 3.4.2 Microbial Activity Variation in Treated-Desalted Cod  
The results of the microbial loads of the control (untreated) and HPP-treated samples are shown in Figure 5. The initial microbial load of the control sample was 2.76 \(\pm\) 0.05, 2.99 \(\pm\) 0.16, 1.15 \(\pm\) 0.15, and 1.85 \(\pm\) 0.01 log CFU/g for TAM, TAP, Enterobacteriaceae, and YM, respectively. [PERSON] et al. (2003) [24] verified similar initial values for TAP counts (2.8 log CFU/g, respectively) but higher YM counts (3.2 log CFU/g). In this study, 6.0 log CFU/g of TAM counts were used as the limit to evaluate microbial spoilage acceptability for consumption [37]. During storage at 4 \({}^{\circ}\)C, TAM (Figure 5A) and TAP (Figure 5B) counts in untreated desalted cod increased (\(p<0.05\)) to 7.15 \(\pm\) 0.21 and 7.62 \(\pm\) 0.09 log CFU/g at the seventh day of storage, respectively, exceeding the acceptable limit for the consumption of 6 log CFU/g. Enterobacteriaceae (Figure 5C) and YM (Figure 5D) counts showed a similar behaviour, with a progressive increase (\(p<0.05\)) over the storage time, reaching values of 5.79 \(\pm\) 0.11 and 4.56 \(\pm\) 0.17 log CFU/g, respectively, at the 14 th day. For all microorganisms, counts were maintained at similar values (\(p>0.05\)) after the 14 th day of storage. Initially (day 0), HPP treatments effectively reduced (\(p<0.05\)) TAM and TAP to values very close to 1.00 log CFU/g, which corresponds to a reduction of about 1.53 and 1.75 log units, respectively. Concerning Enterobacteriaceae and YM, counts in the HPP samples were below the detection limit in both cases (\(<\)1.00 and \(<\)1.70 log CFU/g, respectively) during the total storage time (28 days). Compared to the control samples, a slower TAM and TAP growth rate was observed along storage in HPP-treated samples, showing similar profiles until the day 14 with no significant differences (\(p>0.05\)) between the HPP conditions. Afterwards, TAM and TAP counts increased to values above 6.00 log CFU/g (acceptable limit) at the 21 st day of storage, being observed as slower growth (\(p<0.05\)) occurred in the samples treated at 550 MPa, rather than on those treated at 400 MPa. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Storage Time (Days)**} & \multirow{2}{*}{**Control Desalted Cod**} & \multicolumn{2}{c}{**HPP Desalted Cod**} \\ \cline{3-4}  & & **400 MPa** & **550 MPa** \\ \hline
0 & 6.33 \(\pm\) 0.01 bB & 6.53 \(\pm\) 0.01 aA & 6.54 \(\pm\) 0.01 aA \\
7 & 6.49 \(\pm\) 0.10 aA & 6.53 \(\pm\) 0.09 aA & 6.59 \(\pm\) 0.10 aA \\
14 & 6.50 \(\pm\) 0.04 aA & 6.53 \(\pm\) 0.06 aA & 6.58 \(\pm\) 0.01 aA \\
21 & 6.50 \(\pm\) 0.07 aA & 6.59 \(\pm\) 0.06 aA & 6.51 \(\pm\) 0.04 aA \\
28 & 6.54 \(\pm\) 0.01 aA & 6.59 \(\pm\) 0.09 aA & 6.60 \(\pm\) 0.05 aA \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Variation of pH on control desalted and treated by high-pressure processing (HPP) cod samples during 28 days of storage at 4 \({}^{\circ}\)C. Different letters denote significant differences (\(p<0.05\)) between storage times (a,b) and processing conditions (A,B). These contrasting effects of HPP treatment between microbial groups can be attributed to the difference in resistance levels of these organisms to HPP. Enterobacteriaceae (which regards gram-negative bacteria) and YM are more susceptible to HPP due to their weaker cellular structures, which likely explains why their counts remained below the detection limits. On the other hand, TAM and TAP, particularly mesophiles and psychrophiles, may include other bacteria, especially gram-positive bacteria, which are known to be more pressure-resistant than gram-negative bacteria and YM due to the thick peptidoglycan layer [38]. Similarly, [PERSON] and [PERSON] (2021) [13] study the effect of different packaging methods (vacuum, MAP, and CO\({}_{2}\) emitter) alone or in combination with HPP for the shelf life extension of rehydrated clipfish and saltfish.