## 3 Results and Discussion  
### Thermorheological Behavior of Gluten-Free Matrices  
Monitoring of the thermorheological, textural and color features, as well as the water syneresis of the above systems, was performed in order to assess the quality of the proposed gluten-free matrices. Figure 2 shows the cooling profiles for the control aqueous samples prepared with hybrid carrageenanan (C1) and potato starch (S1), representative of all the tested systems. Note that the matrices formulated with both gelling agents enriched with antioxidant extracts (E1-E7) exhibited the same trends as the corresponding control samples, but with lower magnitudes of both moduli (about eightfold). At a fixed temperature, it was observed that the incorporation of soluble extracts with the highest total phenolic content (Table 1) involved the softest viscoelastic properties, which could be related to increased competition for water between the gelling agents and the antioxidant compounds [19]. The viscous (\(G^{\prime\prime}\)) and elastic (\(G^{\prime}\)) moduli increased with decreasing temperatures. The rise of both moduli was more pronounced for the starch gelled matrices (around six decades for \(G^{\prime}\) and two decades for \(G^{\prime\prime}\)) when compared with the hybrid carrageenanan ones (around three decades for \(G^{\prime}\) and one decade for \(G^{\prime\prime}\)). In all cases, the cooling profiles were consistent with those previously reported for other hybrid carrageenanan [8] and starch solutions [15]. Regardless of the gelling agent used, \(G^{\prime\prime}\) was higher than \(G^{\prime}\) at the highest temperatures (liquid-like behavior). Subsequently, a crossover (tan \(\delta=G^{\prime\prime}/G^{\prime}=1\)) related with the gelling temperature (\(T_{g}\)) was identified. The magnitude of \(T_{g}\) varied between 43 \({}^{\circ}\)C for the C1 system and 67 \({}^{\circ}\)C for the S1 system. The values of this parameter were shifted by the presence of antioxidant soluble extracts (Figure 1b). The determined \(T_{g}\) values were in the range of those reported for this kind of biopolymer [20]. Overall, it was observed that the systems with the lowest total phenolic contents required the highest gelling temperatures. For both gelling agents, the \(T_{g}\) varied significantly, following the order E2 \(\approx\) E3 \(>\) E1 \(\approx\) E5 \(>\) E4 \(\approx\) E6 \(\approx\) E7 \(>\) C1 and E1 \(\approx\) E2 \(\approx\) E3 \(>\) E4 \(\approx\) E5 \(\approx\) E6 \(\approx\) E7. Figure 2: Cooling profiles for (**a**) the control matrices prepared with the hybrid carrageenanan (C1) or potato starch (S1), as well as (**b**) the corresponding gelling temperatures (\(T_{g}\)) for all formulated matrices. Note that in this and subsequent plots, error bars were not presented when they were smaller than the symbol size. After the crossover, a steep increase of the elastic and viscous moduli (with \(G^{\prime}>G^{\prime\prime}\)) was identified, as has been reported for other commonly used gelling agents [21]. It should be indicated that high stability was identified at 85 \({}^{\circ}\)C for all proposed matrices independent of the used extract, achieving straightaway \(G^{\prime}\) and \(G^{\prime\prime}\) moduli which were almost invariant over time (data from time sweeps not shown). These time sweeps highlighted that the dynamic equilibration of the gel network was immediately achieved. This is an interesting feature from the processing point of view, since the required time to reach stable \(G^{\prime}\) and \(G^{\prime\prime}\) moduli after the cooling step varied greatly, depending on the matrix employed [22]. Figure 3 shows the viscoelastic properties of the above gelled matrices, taken after the cooling maturation stage. In all cases, a typical gel profile could be observed (\(G^{\prime}>G^{\prime\prime}\) and both moduli almost invariant over the tested frequency range) [23]. The softening of the gelled matrices in the presence of the tested extracts (E1-E7) was verified with the mechanical spectra.