## 3 Results and Discussion  
### Effect of Water Depuration on Volatile Organic Compounds  
Table 1 presents the main families of VOCs in fish samples subjected to different water deprivation times. Acid derivatives were the most abundant, while phenols, ketones, alcohols, hydrocarbons, and terpenes were present in smaller proportions. Some VOCs increase with longer fish washing times, as removing off-flavor aromatic compounds during washing may enhance the detection of certain compounds with pleasant aromas that intensify with increased washing. This applies to phenol, alcohol, and hydrocarbon families, which are compounds responsible for positive aromas. The phenol group doubled after 48 h of sample washing. Additionally, after 24 h of water depuration, alcohol groups increased significantly. These aromas are related to a fish-like, green, citrus, or fruity odor [22]. Hydrocarbons were the second most important VOCs, showing an increase of 20% in fish subjected to longer washing times compared with fish submitted to no washing treatment (0 h). As per [PERSON] et al. [23], hydrocarbons may result from the degradation of fatty acids, contributing to a sweet flavor. By contrast, families of VOCs such as ketones, terpenes, and acid derivatives were found in greater proportions in trench that spent less time in washing ponds (0 h, 12 h, and 24 h), with levels being 10-20% higher the in initial treatments. Acid derivatives were the most represented VOCs throughout the treatments. However, a significant aroma reduction occurred after 24 h, and content levels equalized from 48 h onward. Figure 2 shows the main VOCs associated with off-flavor aromas, namely 3,5,5-trimethyl-1-hexene (TMH), dimethyl-8-hydronaphalen (GEO), 1-octen-3-ol (OCT), diethyl phthalate (DEP), 2-methylisoborneol (MIB), and \(\alpha\)-isomethylionone (IML). The highest VOC concentrations (Figure 2) were observed in the treatment at 0 h, and it gradually decreased in all fish subjected to the higher-intensity deputation process with clean water. In fact, after 24 h, these VOCs decreased by 50%, continuing to drop after 48 h, with some compounds such as \(\alpha\)-isomethylionone showing non-detectable levels. The key VOCs responsible for off-flavor aromas, as highlighted by the existing literature, are dimethyl-8-hydronaphalen, also known as geosmin, and 2-methylisoborneol [3]. Although not present in high concentrations, these compounds play a crucial role in the unpleasant aroma associated with freshwater fish, particularly benthic species like tench. Notably, diethyl phthalate had the highest concentration in this study, peaking in the washing treatments at 0 h. Diethyl phthalate is a phthalic acid ester commonly used in plastics or cosmetics, has a characteristic unpleasant odor, and is recognized as a pollutant [24]. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **0 h** & **12 h** & **24 h** & **48 h** & **72 h** & **96 h** \\ \hline Hydrocarbons & 10.7 \(\pm\) 1.3 & 12.5 \(\pm\) 1.1 & 12.1 \(\pm\) 1.0 & 16.7 \(\pm\) 1.2 & 15.4 \(\pm\) 1.5 & 15.8 \(\pm\) 1.6 \\ Alcohols & 8.5 \(\pm\) 1.4 & 7.8 \(\pm\) 1.1 & 12.7 \(\pm\) 0.3 & 17.9 \(\pm\) 1.3 & 18.8 \(\pm\) 1.6 & 21.4 \(\pm\) 2.2 \\ Acid & 59.1 \(\pm\) 2.1 & 58.7 \(\pm\) 1.1 & 54.6 \(\pm\) 3.2 & 48.5 \(\pm\) 2.6 & 47.7 \(\pm\) 3.8 & 45.1 \(\pm\) 5.4 \\ derivates & 12.5 \(\pm\) 1.0 & 11.1 \(\pm\) 1.3 & 11.5 \(\pm\) 1.3 & 9.9 \(\pm\) 1.1 & 9.0 \(\pm\) 1.2 & 9.5 \(\pm\) 2.1 \\ Terpenes & 6.9 \(\pm\) 2.1 & 7.7 \(\pm\) 1.0 & 6.8 \(\pm\) 1.5 & 2.1 \(\pm\) 0.3 & 4.8 \(\pm\) 0.6 & 4.1 \(\pm\) 0.6 \\ Phenols & 2.3 \(\pm\) 0.6 & 2.2 \(\pm\) 0.5 & 2.1 \(\pm\) 0.5 & 4.7 \(\pm\) 1.2 & 4.1 \(\pm\) 1.1 & 3.8 \(\pm\) 0.6 \\ \hline \In the samples, 1-octen-3-ol, an unsaturated alcohol characterized by its contribution of a'mushroom-like' and 'raw mushroom' flavor [25] and that is synthesized by different species of microorganisms [22], was identified. [PERSON] et al.