## 3 Results and Discussion
### Assessment of Lipid Oxidation Development
Such molecules are likely to degrade, leading to low molecular weight compound formation or reaction with other compounds included in the fish muscle. Thus, the determination of each kind of compound cannot always afford a valuable method for assessment of the quality degradation in fish. A relevant increase in the CD, CT and TBARS values was observed in the present study. The high reactivity or the electrophilic character of lipid oxidation compounds in general led them to break down or react with food constituents possessing nucleophilic groups (i.e., -NH\({}_{2}\) and -SH functions) [63; 64; 65; 66]. As a result, a remarkable increase in the presence of fluorescent compounds (tertiary lipid oxidation compounds) was observed [67; 68]. It is concluded that lipid-related indices (CD, CT, TBA and FR values) are valuable tools for assessing the lipid damage development of the current species under chilling conditions. Contrary to this, the PV did not afford an accurate measurement of the oxidation degree as being an indication of the initiation of lipid oxidation [26; 61]. To the best of our knowledge, no previous information is available regarding the lipid oxidation development of pouting during refrigerated storage. However, lipid oxidation development in pouting muscle has been described when subjected to other technological treatments. Thus, an important fluorescent compound formation was detected in a heated muscle system (25 d at 30 \({}^{\circ}\)C) [24]. However, no increase in the TBA value was detected by [PERSON] et al. [19] in frozen pouting muscle after 6 months of storage at \(-20\) \({}^{\circ}\)C.  
Previous reports accounted for the assessment of lipid oxidation development in lean fish species during chilled storage. According to these reports, low peroxide formation was detected in chilled hake (_M. merlucius_) (3.7 meq.kg\({}^{-1}\) lipids after 8 d) [58] and turbot (_P. maxima_) (2.9 meq.kg\({}^{-1}\) lipids after 9 d) [59]. However, relevant peroxide formation was observed in Atlantic pomfret (_B. brama_) (12.1-15.3 meq. active oxygen\(\cdot\)kg\({}^{-1}\) lipids) after a 9 day storage period [52]. A marked increase in peroxide formation was detected in an underutilized species, Bombay duck (_H. nehereus_), (ca. 25 meq. active oxygen\(\cdot\)kg\({}^{-1}\) lipids), after 13 d of storage [46]. In agreement with the present study, TBARS formation has been detected in chilled lean fish. Thus, relatively low TBARS formation was detected in Atlantic pomfret (_B. brama_) (0.2-0.3 mg malondialdehydedehyde\(\cdot\)kg\({}^{-1}\) muscle range value after a 15 day storage period) [52] and wild turbot (_S. maximus_) (0.5 mg malondialdehydedehyde\(\cdot\)kg\({}^{-1}\) muscle value after a 19 day storage period) [51]. On the contrary, greater formation was observed in sea bream (_S. aurata_) and farmed sea bass (_D. labrax_) after an 18 day storage period in ice (1.4 and 1.0 mg malondialdehydedehyde\(\cdot\)kg\({}^{-1}\) muscle values, respectively) [45]. Regarding underutilized lean species, lobster krill (_Munida_ sp.) exhibited a 0.13 mg malondialdehydedehyde\(\cdot\)kg\({}^{-1}\) muscle value after a 10 day storage period [11]. Finally, progressive formation of fluorescent compounds was detected in related lean species during the storage time. These results refer to Atlantic pomfret (_B. brama_) [52], European hake (_M. merlucius_) [58] and lobster krill (_Munida_ sp.) [11].