# An Overview of the Alternative Use of Seaweeds to Produce Safe and Sustainable Bio-Packaging
## 3 Physicochemical Characteristics of Seaweeds Phyccolloids  
The hydrocolloidal and gelling properties of phyccolloids in seaweeds are dependent on their polymer structure, concentration in a solution, temperature, pH, and syneresis potential [79; 80; 81]. The physicochemical quality of phyccolloids is heavily influenced by the seaweed species, environmental conditions, extraction methods, and treatment processes [79; 82]; thus, a deep understanding of these factors will allow us to discover the most efficient techniques to obtain high-quality phyccolloids. In the form of salts, carrageenanans possess high gel strength [83]. Both \(\kappa\)-carrageenanan and \(\iota\)-carrageenanan gels are stable at room temperature. One exception is \(\lambda\)-carrageenanan, which has typical nongelling property, and is the only cold-water soluble carrageenanan in its native form. According to [PERSON] et al. [84], \(\kappa\)-carrageenanan enriched with cations enhances the gel formation and strength of phyccolloids. [PERSON] et al. [85] studied the physical properties of glycerol-plasticized edible films made with \(\kappa\)-carrageenanan, \(\iota\)-carrageenanan, and alginate; \(\kappa\)-carrageenanan exhibited higher tensile strength and elasticity, higher moisture permeability, and lower opacity compared to \(\iota\)-carrageenanan, while alginate films revealed higher transparency [85]. Similar to carrageenanan, alginate also forms rigid and stable gel matrix in the presence cations, especially Ca\({}^{2+}\)[86]. Films obtained from sodium alginate with 1%-3% (_w/v_) calcium chloride solution exhibited an increase in tensile strength and elongation properties, and reduced opacity [87; 88]. Agar films, compared to carrageenanan and alginate films, have a lower tensile strength and water vapor permeability. On the other hand, they exhibit twice the elongation value  
Figure 3: Chemical structure of agarose polymer. of \(\kappa\)-carrageenanan film, and with better elasticity [89, 90]. Due to their gelling properties and viscosity, seaweed phycocolloids are widely used as stabilizers and/or thickening and gelling agents in the manufacturing of food, pharmaceuticals, and cosmetics. With new methodologies, it has been possible to investigate the behaviour of these seaweed-derived compounds when incorporated into biofilms, and thus to use them as potential candidates to develop biofilms and packaging [91, 92, 93, 94]. Different methods of film formation had significant effects on the physical properties and microstructures of the film. An example is given by [PERSON] et al. [95], in which chitosan-alginate films were produced through different processes. Their results showed that biofilm prepared through layer-by-layer assembly combined with ferulic acid crosslinking has enhanced mechanical properties, opacity, and hydrophobicity compared to films prepared by direct mixing, crosslinking alone, and layer-by-layer assembly alone. Seaweed-derived bioactive compounds possess biological properties that can assure the safety of the packaged product [96]. Due to their biocompatibility, non-cytotoxicity, and antimicrobial properties, biopolymers from seaweeds are excellent candidates to develop safe packaging for food and pharmaceuticals [97]. Bioplastics made from extracted, seaweed-derived biopolymers are reported to be more resistant to microwave radiation due to the photoproduction properties of seaweed compounds, and thus can conserve the quality of packaging for food or pharmaceuticals [98]. The extraction of carrageenanan and agar typically involves hot water as a solvent, as they possess great solubility. Alginate, on the other hand, requires hot alkali as the major solvent, as alginic acid is composed of water-insoluble salts. Thus, through alkali extraction, alginate salts are converted into water-soluble alginate salts.