# Evaluation and Characterization of Alginate Extracted from Brown Seaweed Collected in the Red Sea
###### Abstract  
Alginates are one of the most important compounds of brown seaweeds. These compounds are employed in the food area, because of their important rheological properties, such as viscosity, gelling, and stabilizing features and as dietary fiber source. In this study, five species of dominant brown seaweeds were collected in the Red Sea (_Padina boregessini, Turbinaria triquetra, Hormophysa cuneiformis, Dictyota ciliolata,_ and _Sargassum aquifolium_) so as to characterize the alginate yield and its properties. The analysis demonstrated differences in the alginate yield among the seaweeds. The highest yield of alginate was recorded in the species _T. triquetra_ (22.2 \(\pm\) 0.56% DW), while the lowest content was observed in _H. cuneiformis_ (13.3 \(\pm\) 0.52% DW). The viscosity from the alginate varied greatly between the species, whereas the pH varied slightly. The alginate exhibited a moisture content between 6.4 and 13.1%, the ash content ranged between 12.3 and 20% DW, the protein reached values from 0.57 to 1.47% DW, and the lipid concentration varied from 0.3 to 3.5% DW. Thus, the phytochemical analysis demonstrated that the extracted aginates can be safely applied in the food industry. Furthermore, the alginate yield reveals the potential application of these seaweeds as a nutraceutical raw source, which can be exploited by the food industry. alginate; dietary fiber; Red Sea; physicochemical properties; phytochemical properties; nutritional +
Footnote †: journal: Medical  
food processing. This safety record is mainly determined by analyzing its phytochemicalen properties and protein content (purity rate or polysaccharide quality level) [12; 13]. If the polysaccharide purity rate is high, these polysaccharides show interesting rheological properties [14], as well as biodegradability, biocompatibility, and the absence of toxicity [6]. If the polysaccharide demonstrates a high rate of impurities, it can have adverse effects on human health, and their application in the food, pharmaceutical, and biomedical areas is not recommended [15]. This is very explicit and restrictive by the authorities from Europe and United States of America so as to guarantee a safe human intake with low adverse effects [16; 17]. The low adverse effects are mainly the results of an overdosage of a specific nutrient, and the excessive dietary fiber ingestion results in soft stools or diarrhea symptomatology [18; 19]. Alginate, the main polysaccharide synthesized by brown seaweeds, is one of the most exploited polysaccharides in the food industry, because of its inherent and excellent properties as a thickener and stabilizer agent in processed foods [2]. It presents positive features for the food industry, such as being low cost, easy to incorporate into food, being well accepted for human food consumption, and quick to adapt for a specific role [2; 20]. Alginic acid is the main structural polysaccharide present in the cell wall and in the intercellular matrix of brown seaweed, providing flexibility and mechanical resistance to the force of the water in the marine environment where the seaweed grows [21]. Alginic acid is a complex organic compound composed of monomers of d-manuronic acid and l-galuronic acid. So, alginate is composed of 1, 4-\(\beta\)-d-manuronic acid (M) and 1, 4-\(\alpha\)-l-galuronic acid (G) monomers, with a homogeneous (Poly-M and Poly-G) or heterogeneous (MG) block configuration. The extraction process is based on the conversion of an insoluble mixture of salts of alginic acid into a soluble salt (alginate), which is suitable for water extraction [2; 22; 23]. The proportion of the three kinds of blocks, namely GG, MM, and MG, defines the physical features of alginates, with alginates with a high proportion of M blocks having a higher viscosity, while those with a high proportion of G blocks having higher gelling properties [2; 24]. Alginates vary in composition among species, from 20 to 60% dry matter, and occur mainly as gels comprising magnesium, calcium, sodium, and barium ions [25].