## 3 Results and Discussion
### Characterization of Edible Coating Solutions  
Carrageenan and alginate coating solutions, prepared as described in Section 2.4, were supplemented with _P. canaliculata_ ethanolic extract at concentrations ranging from 0% to 1% (\(m/v\)), resulting in a total of 12 solutions. Each solution was then characterized for total phenolic content and antioxidant activity by the DPPH method (Figure 1). These assays aimed to evaluate the effect of the binomial extract-polysaccharide on the coating solution properties.  
In general, an increase in phenolic content (Figure 1A) and antioxidant activity (Figure 1B) was observed with increasing _P. canaliculata_ extract concentration in both carrageenan and alginate coating solutions. Moreover, coating solutions without extract addition (0%) showed no antioxidant activity or phenolic content. However, some differences between the two base coating solutions were detected. Analysing the results of the DPPH assays, it was evident that alginate-based solutions consistently presented higher antioxidant activity compared to carrageenan solutions at the same extract concentration. Carrageenan with 1% extract achieved an antioxidant activity of 0.66 \(\pm\) 0.01 mg Trolox per mL, which was clearly lower than alginate with the same extract concentration (0.81 \(\pm\) 0.01 mg/mL) and similar to the value for alginate with 0.5% extract (0.61 \(\pm\) 0.1% mg/mL). This differ  
Figure 1: **(A)** Total phenolic content and (**B**) DPPH antioxidant activity of carrageenan and alginate coating solutions supplemented with ethanolic extract of _P. canaliculata_ at concentrations ranging from 0% to 1%.  
ence between the two base solutions is further supported by the IC50 values, the extract concentration capable of inhibiting 50% of the DPPH radical, which were 0.96% and 0.50% for carrageenan and alginate base solutions, respectively. However, this difference was not observed in the total phenolic content results, as the highest TPC values were found in carrageenan solutions.  
These results may be explained based on the distinct bounds that are established between polysaccharide coatings and the phenolic compound from the extracts, which potentially affects their reactivity in both DPPH and Folin assays. In fact, only the free hydroxyl groups are able to undergo redox reactions, being detected in the Folin-Ciocalteu assay [38; 39]. Also, the results of the DPPH method, which measures the free radical scavenging ability of antioxidants, can be influenced by several factors attributed to polysaccharide matrices. In fact, physical entrapment of antioxidants and the barrier effect of matrices, as well as their interference with the solubility or dispersion of phenolic compounds, have been reported [40]. However, a more insightful explanation for the observed differences would require a detailed analysis of the phenolic profile of the algae extract.  
Aiming to select the appropriate extract concentration to apply in both base coating solutions for frying assays, a compromise strategy was adopted. Although increasing the extract concentration resulted in higher DPPH and TPC values, it also adversely affected the rheological properties of the coating solution, namely its viscosity and, consequently, its adhesion to the food matrix. Therefore, the extract concentration corresponding to the DPPH IC\({}_{50}\) value was selected, i.e., 1% for carrageenanan-based and 0.5% for alginate-based coatings (Table 1).