## 3 Results and Discussion
### Assessment of Lipid Oxidation Development  
The development of lipid oxidation in pouting muscle was determined at different stages of this damage mechanism. Thus, the formation of CD and CT compounds indicated progressive formation (\(p<0.05\)) of these kinds of molecules during chilling storage (Table 3). The CD content depicted a fair correlation value with the chilling time (\(r=0.88\), quadratic fitting), while better correlation was detected for the CT value (\(r=0.93\), quadratic fitting). Compared with the lipid hydrolysis evolution (i.e., the FFA value), a fair correlation value for the CD content (\(r=0.90\)) and a better one for the CT level (\(r=0.94\)) were observed. Figure 2: Formation of free fatty acids (FFAs; g\(\cdot\)kg\({}^{-1}\) lipids) in pouting muscle subjected to chilling storage. Average values of three independent determinations (\(n=3\)), where standard deviations are denoted by bars. Different letters (a, b, c and d) denote differences (\(p<0.05\)) in chilling time. Regarding peroxide formation (Table 3), the levels found for this kind of oxidation compound were roughly in the 1.2-2.2 meq. active oxygen: kg\({}^{-1}\) lipid range throughout the whole study. This range can be considered especially low if we compare it to the values found for other fish species stored under similar processing conditions [26; 60; 61]. Due to the effect of the storage time, a small increase (\(p<0.05\)) was achieved on day 3, but no differences (\(p>0.05\)) were subsequently detected for the 3-9 day storage times in this study. The determination of the secondary lipid oxidation compounds (i.e., TBARSs) indicated progressive formation (\(p<0.05\)) as the chilling time increased (\(r=0.94\)) (Table 3). Thus, an increase (\(p<0.05\)) was detected after 3 and 6 d of storage, but no effect (\(p>0.05\)) was detected at the end of the study. Fair correlation values (\(r=0.87\)) for the TBA index with the CD and CT values were determined. The investigation of the FR indicated relevant formation (\(p<0.05\)) of interaction compounds after 6 and 9 d of chilling storage (Figure 3). Thus, good correlation with the chilling time was achieved (\(r=0.91\), quadratic fitting). Good correlation values were also detected with other lipid quality indices, such as the FFA (\(r=0.94\)) and CT (\(r=0.91\)) values. Figure 3: Fluorescent compound formation (fluorescence ratio (FR)) in pouting muscle subjected to chilling storage. Average values of three independent determinations (\(n=3\)), with standard deviations indicated by bars. Different letters (a, b and c) denote differences (\(p<0.05\)) in chilling time. \begin{table}
\begin{tabular}{c c c c c} \hline
**Lipid Oxidation Index** & \multicolumn{4}{c}{**Chilling Time (Days)**} \\ \hline  & **0** & **3** & **6** & **9** \\ \hline Conjugated dienes & 0.46 \(\pm\) 0.04 a & 0.56 \(\pm\) 0.02 b & 0.55 \(\pm\) 0.02 b & 0.70 \(\pm\) 0.07 c \\ (absorbance: mL sample:mg\({}^{-1}\) sample) & 0.053 \(\pm\) 0.010 a & 0.068 \(\pm\) 0.007 ab & 0.076 \(\pm\) 0.006 b & 0.116 \(\pm\) 0.048 c \\ (absorbance: mL sample:mg\({}^{-1}\) sample) & 1.29 \(\pm\) 0.17 a & 2.18 \(\pm\) 0.24 b & 2.00 \(\pm\) 0.19 b & 2.17 \(\pm\) 0.11 b \\ (meq. active oxygen:kg\({}^{-1}\) lipids) & 1.29 \(\pm\) 0.17 a & 2.18 \(\pm\) 0.24 b & 2.00 \(\pm\) 0.19 b & 2.17 \(\pm\) 0.11 b \\ \hline Thiborbituric acid index & & & & \\ (mg malondialdehydedehyde-kg\({}^{-1}\) muscle) & 0.09 \(\pm\) 0.02 a & 0.43 \(\pm\) 0.10 b & 0.68 \(\pm\) 0.04 c & 0.88 \(\pm\) 0.29 c \\ \hline \end{tabular}  
* Average values \(\pm\) standard deviations of three independent determinations (\(n=3\)). ** In each row, different letters (a, b and c) denote differences (\(p<0.05\)) in chilling time.  
\end{table} 
Table 3: Assessment of lipid oxidation events * in pouting muscle subjected to chilling storage **. The lipid oxidation mechanism has been described as a complex process in which different types of molecules are produced, with most of them being unstable [61; 62].