Extraction and modification of brown algae-derived sodium alginate by ozonation: Characterization and behavior at different pH levels

Alginate, a biopolymer found in brown algae, has diverse physicochemical properties that enable its broad application across various industries. Ozone gas stands out as an innovative tool for modifying alginate, with potential benefits in enhancing properties, such as gel strength, hydrophobicity, and biodegradability. This study evaluated ozone-induced modifications in sodium alginate (SA) extracted from Sargassum cymosum C. Agardh, offering valuable insights into structural and physicochemical changes and potential industrial applications. Ozone-treated SA maintained its chemical integrity and thermal stability. Total color difference (ΔE) analysis revealed that the native sample had a significantly greater deviation from commercial SA than the ozonized sample, likely due to the bleaching effect induced by ozonation. Significant SA chain depolymerization occurred after ozonation, reducing the average molecular weight and viscosity. Rheological analysis demonstrated pH-dependent behavior, with commercial and ozonized samples having similar Newtonian characteristics. Polydispersity index analysis showed a uniform molecular size distribution, and the zeta potential decreased after ozonation. These properties can be explored, for example, in gel formation. These findings enhance our understanding of modified SA applications, addressing a significant knowledge gap.