## 3 Results and Discussion
### Characterization of Fried Mackerel Fillets
#### 3.3.3 Nutritional Characterization of Fried Mackerel Filllets
At frying temperature, highly reactive peroxyl and alkyl radicals are formed, leading to chain reactions that result in PUFA degradation and formation of secondary oxidation compounds, namely volatile and polar compounds [11]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**FA** & **Control** & **Alg** & **Alg Pc** & **Car** & **Car Pc** \\ \hline C12:0 & 0.08 \(\pm\) 0.02 & 0.07 \(\pm\) 0.02 & 0.05 \(\pm\) 0.01 & 0.06 \(\pm\) 0.02 & 0.07 \(\pm\) 0.01 \\ C13:0 & 0.10 \(\  
The results obtained suggest that both alginate- and carrageenanan-based coatings promoted higher degradation of C18:2 since considerably lower values of this FA were found in Alg, Car, and Car Pc, in comparison with the control. Nevertheless, _P. canaliculata_ extract seemed to have a protective effect on preventing C18:2 degradation in the alginate matrix, since 10 times higher values were observed in Alg Pc (21.4 \(\pm\) 1.8%) compared to Alg (2.39 \(\pm\) 0.16%). Considering that the FA profile was expressed as a percentage of total FA, a remarkable decrease in C18:2 may have influenced the remaining values. This can explain the results attained for oleic (C18:1), the most abundant FA in all the samples. In fact, the highest amounts of this MUFA, ranging from 37.49 \(\pm\) 0.36% to 44.94 \(\pm\) 0.95%, were found in samples with lower C18:2 values (in Car, Alg, and Car Pc samples), while Alg Pc and Control had similar values (27.14 \(\pm\) 0.66% and 24.56 \(\pm\) 0.10%, respectively). This hypothesis requires an in-depth study of the microstructure of coatings, as well as analyses of fatty acid degradation products. The fatty acid profile determines the nutritional quality of foods. Several health lipid indices are usually used to evaluate fat quality. It is well established that an n-3/n-6 ratio between 1:1 and 5:1 is recommended to help prevent several chronic diseases. Moreover, the ratio between hypocholesterolemomic (C18:1 and PUFA) and hypercholesterolemia (C14:0 and C16:0) fatty acids, known as the h/H index, is used to assess the effect of the FA profile in cholesterol metabolism, being recommended as a nutritional evaluation tool. The atherogenic index (AI), which is used to assess the risk for cardiovascular diseases, relates the proportion between the proatherogenic SFA and the main classes of antiatherogenic unsaturated fatty acids (UFA). The thrombogenic index (TI) is related to the tendency for clot formation in the blood vessels, corresponding to the relationship between the prothrombinogenic (SFA) and antithrombotic fatty acids (MUFA, n-6 and n-3 PUFA). Values lower than 1.0 and 0.5 for AI and TI, respectively, are desirable for a health-promoting diet [34]. In this study, higher values of the n3/n6 ratio (4.27 \(\pm\) 0.19 in Car Pc to 5.02 \(\pm\) 0.19 in Alg) were observed for samples with the lowest content of C18:2, conversely to those of the control (1.21 \(\pm\) 0.05) and Alg Pc (0.80 \(\pm\) 0.04). The coated fillets supplemented with _P. canaliculata_ exhibited better health lipid indices. In fact, significantly higher values of h/H were attained for Alg Pc (3.55 \(\pm\) 0.46) and Car Pc (3.34 \(\pm\) 0.05) in comparison with the control (2.67 \(\pm\) 0.05). Moreover, the best values of AI index were attained for Alg Pc (0.40 \(\pm\) 0.04) and Car Pc (0.41 \(\pm\) 0.01) in contrast to the control sample (0.52 \(\pm\) 0.01). No statistically significant differences were observed for the TI index, with values around 0.3 for all the samples.