# Evaluation and Characterization of Alginate Extracted from Brown Seaweed Collected in the Red Sea
## 2 Materials and Methods
### Biochemical Composition of the Extracted Sodium Alginate
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Species**} & **\% of Dietary** & **g of Seaweed DW for** & **g of Dietary Fiber for 5** & **\% of the RDFI/5g of** \\  & **Fiber/Seaweed DW** & **25 g of Dietary Fiber** & **g of Seaweed DW** & **Seaweed DW** \\ \hline _D. ciliulata_ & 20.2 \(\pm\) 1.1 & 123.76 & 1.01 & 4 \\ _H. cuneiformis_ & 13.3 \(\pm\) 0.52 & 187.97 & 0.67 & 2.68 \\ _P. beorgesenti_ & 16.6 \(\pm\) 1.2 & 150.60 & 0.83 & 3.32 \\ _S. aquifolium_ & 18.3 \(\pm\) 1.2 & 136.61 & 0.92 & 3.68 \\ _T. triquetta_ & 22.2 \(\pm\) 0.56 & 112.61 & 1.11 & 4.44 \\ \hline \end{tabular}
\end{table} 
Table 6: Thresholds of daily consumption of seaweeds based on their polysaccharide content. be concluded that they are in accordance with the quality standards established by the food industry. The rheological features are a key factor in the use and application of alignates in the food industry [7]. In the present study, the viscosity of sodium alginate was significantly different between species, ranging from 57.6 to 134.4 cP. However, the results obtained are in accordance with the FCC standard. The FCC authorizes sodium alginate viscosities between 10 to 5000 cP. Nevertheless, the viscosity of the alginate is affected by several factors, such as the proportion of M and G units in the extracted alginate, the temperature, and the acidic media [68]. To determine and identify the presence of functional groups in alginate, FTIR spectroscopy analysis was used [23; 69]. In this study, the FTIR analysis revealed that the band at 947 cm\({}^{-1}\) (elongation vibration C-O of uronic acid residues) and the small band at 903 cm\({}^{-1}\) are attributed to C-H of \(\alpha\)-L guluronic acid. Mannuronic units have a band at approximately 1025 cm\({}^{-1}\), while guluronic units have a band at 1082 cm\({}^{-1}\). The 872 cm\({}^{-1}\) band is typical of \(\beta\)-mannuronic acid residues. In our spectrum, it was observed that the presence of a band around 1025 cm\({}^{-1}\) (M blocks) is slightly more intense than the band around 1082 cm\({}^{-1}\) (G blocks), suggesting that our alginate is slightly richer in mannuronic residues than in guluronic residues [23; 42; 70]. However, this method lacks quantification precision. All of the spectra of isolated alignates are very comparable to those of commercial standard sodium alginate (Sigma-Aldrich, Gillingham, UK), as reported by [PERSON] et al. [42], showing similar locations of the characteristic bands. Furthermore, when using FTIR, it the peaks of other compounds were not detected, such as Phlorotannins or carotenoids, which can be bonded to alginate in the seaweed cell walls [71]. For the determination of the composition, structure, M/G ratio, and block distribution of alignates, \({}^{1}\)H-NMR was used [69]. The sodium alginate extracted from all of the studied brown algae revealed characteristic spectra similar to the commercial sodium alginate, as reported by [PERSON] et al. [42]. This study [42] also demonstrates that alignates with a high M/G ratio have more elastic tension, which is more desirable for the food industry (as a thickener, gel, emulsifier, flavor enhancer, and stabilizer), and also in cosmetic or pharmaceutical areas [42; 72]. Although with similar conformation, the alginate viscosity difference can be derivated in the alternance of GG, MM, or MG units within the species analyzed, which are important to alginate viscosity and moisture retention [42]. Additionally, other impurities that alginate has, such as proteins and lipids, also contribute to variations in viscosity. Another important parameter to analyze before applying sodium alginate in the food and biomedical fields is the alginate purity yield. The phytochemical characteristics results indicate that the sodium alginate extracted from different brown seaweeds do not have terpenoids, tannins, glycosides, phlorotannins, flavonoids, phenols, steroids, and alkaloids. Similarly, [PERSON] et al. [12] and [PERSON] et al.