## 4 Discussion
The extraction efficiency and properties of alignates are influenced by various parameters, such as temperature, extraction time, pH, sample size and the alkaline extraction used [83]. Statistical analysis revealed that both the extraction temperature and the seaweed sample had highly significant effects on the extraction yield of alginate (\(p<0.001\)), along with a significant interaction effect. This indicates that the impact of temperature on yield is dependent on the biomass source used. Post hoc Tukey HSD tests showed that all tested temperatures (25 \({}^{\circ}\)C, 60 \({}^{\circ}\)C, and 80 \({}^{\circ}\)C) differed significantly in terms of extraction yield, with mean values increasing as the temperature increased. This trend suggests that higher temperatures enhance alginate solubilization from the cell wall, possibly due to increased molecular mobility and disruption of intermolecular interactions. Regarding the biomass type, all sample groups differed significantly from each other. Our extractions yielded 7.33 to 51.04% dw of alignates, with _L. ochroleuca_ registering the lowest yield at 25 \({}^{\circ}\)C extraction and the residual pulp the highest. Lower results were obtained by [PERSON] et al. [74], while a similar yield was obtained for _S. polyschides_ and _L. ochroleuca_ by [PERSON] et al. [84]. As for _M. pyrifera_, the best values were obtained at 80 \({}^{\circ}\)C, which were higher than those obtained by [PERSON] et al. [43]. These differences may be attributed to the extent of cell wall degradation and intrinsic alginate content. The significant interaction between temperature and biomass type further highlights that extraction efficiency is not governed by a single factor, providing a clear indication of the variation between species and the need to optimize the extraction protocols for each of them. Specifically, regarding the _M. pyrifera_ residual biomass, our results show that the highest extraction yield was obtained with an extraction temperature of 60 \({}^{\circ}\)C. In all the extractions, and regardless of the extraction temperature, the residual biomass always showed higher alginate extraction yield values. Figure 2A shows that the cell wall of the algal biomass of _M. pyrifera_ had a well-organized cell structure compared to the structure of the residual pulp, which was disrupted due to the aqueous extraction, an aspect that is clearly visible in Figure 2B. It is likely that this cellular disintegration, resulting from the processing, fostered the release of alginate and improved the overall efficiency of the extraction. As far as the FTIR analysis is concerned, the most prominent absorption peaks found correspond to the functional groups typically associated with sodium alginate. Between the wavelengths of 3000 and 3500 cm\({}^{-1}\), water is typically found [9; 85]. Characteristic peakswere detected around 1600 cm\({}^{-1}\) and 1400 cm\({}^{-1}\), which are indicative of asymmetric and symmetric stretching vibrations of the carboxylate (-COO\({}^{-}\)) groups, respectively, key functional groups in the alginate backbone [9]. These confirm the presence of uronic acids, such as galuronic (G) and mannuronic (M) acid residues, which constitute the main structural components of alginate. In the region between 3000 and 3500 cm\({}^{-1}\), a broad absorption band was observed, which is commonly attributed to the O-H stretching vibrations of hydroxyl groups and adsorbed water molecules [86]. This is typical in polysaccharide samples and reflects both the intrinsic hydrophilicity of alginate and the moisture retained within the matrix or bound to its structure. The intensity of this band may also be influenced by residual humidity or hydrogen bonding within the polymer network. Overall, the FTIR spectral profile supports the presence of alginate and related polysaccharides in the sample and can also be used as a rapid tool for confirming functional group integrity following extraction processes.