# Physicochemical and Microbiological Changes Associated with Processing in Dry-Cured Tuna
## 3 Results and Discussion
### Biochemical Parameters  
Table 3 shows the changes in the total volatile base nitrogen (TVBN) and lipid oxidation test values during the _mojama_ elaboration process. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **Raw Tuna** & **Salting** & **Salt-Washing** & **Dry-Cured Tuna** & \(p\)**-Value** \\ \hline TVBN (mg/100 g) & mean \(\pm\) SD & 34.00 \(\pm\) 0.85 b & 31.00 \(\pm\) 1.71 bc & 28.42 \(\pm\) 2.97 c & 52.67 \(\pm\) 5.68 a & *** \\  & range & 33.00–35.00 & 28.00–34.00 & 25.00–34.00 & 45.00–57.00 & \\ \hline TBARS (mg MDA/kg) & mean \(\pm\) SD & 1.37 \(\pm\) 0.98 b & 4.04 \(\pm\) 1.87 ab & 2.05 \(\pm\) 1.18 ab & 5.56 \(\pm\) 4.11 a & * \\  & range & \textless{}LOD–3.36 & \textless{}LOD–7.52 & \textless{}LOD–4.06 & \textless{}LOD–15.37 & \\ \hline \hline \end{tabular}  
* Different letters in the same row indicate significant differences by [PERSON]’s test. *, ***–significant at \(p\) \(<\) 0.05 and \(p\) \(<\) 0.001, respectively. SD—standard deviation. LOD—limit of detection.  
\end{table} 
Table 3: Changes in malondialdehydedehyde (MDA) and total volatile basic nitrogen (TVBN) content of yellowfin tuna during the _mojama_ elaboration process. The TVBN is one of the most widely used measurements for evaluating fish quality, this being one of the most common chemical indicators for fish spoilage [52]. This parameter includes the measurement of trimethylamine (produced by spoilage bacteria), dimethylamine (produced by autolytic enzymes), ammonia (produced by the deamination of amino acids and nucleotide catalogues), and other volatile basic nitrogenous compounds associated with fish spoilage [53]. In our study, the values of TVBN in raw tuna were 34 mg/100 g on average. The significant decrease in this value for the samples obtained after the salt-washing step (28.42 mg/100 g) could be explained by the fact that some of the TVBN compounds diffused into the water together with the other nitrogen fractions. An increase in this value was observed for the samples obtained after the drying step (52.67 mg/100 g), resulting from the concentration effect caused by the water loss. The degradation of proteins due to protein oxidation during the manufacturing process has been identified as a contributing factor to the accumulation of TVBN in fish products [54; 55]. To ensure the safety and quality of _mojama_, it is important to control the processing stages that can affect TVBN levels. For example, parameters such as salting and drying time, salt concentration, and storage temperature, and humidity can help minimize the increase in TVBN levels during processing. Proper storage and handling practices can also prevent the growth of spoilage bacteria and ensure the safety and freshness of tuna products. Several studies have reported a correlation between TVBN levels and fish freshness [56; 57; 58], but there is controversy regarding the use of TVBN as the sole indicator of fish freshness [59; 60]. While TVBN levels are a useful indicator of the degree of spoilage in fish, they do not provide a complete picture of the freshness of fish. Other factors, such as the presence of specific volatile organic compounds (VOCs), color, and pH, can also be important indicators of freshness [60]. Furthermore, the relationship between TVBN levels and the sensory quality of fish may vary depending on the fish species, storage conditions, and other factors. For instance, some fish species may have high levels of TVBN naturally occurring in fresh fish, while other species even during spoiling may present low levels of TVBN [61], in conclusion, the TVBN data should be evaluated together with other complementary parameters for checking the freshness of the fish. On the other hand, MDA is commonly used as a marker for oxidation in fish, this being a product of the oxidation of polyunsaturated fatty acids. The development of lipid oxidation is an indicator of the enzymatic reaction and changes in non-enzymatic free radicals [62].