In recent years, research on edible films has gained considerable popularity due to the potential use of biodegradable packaging. In this study, sodium alginate was extracted from the brown alga sargassum angostifolium, collected from the shores of the Persian Gulf (Bushehr province), and its structure and physicochemical properties were investigated. Alginate extraction was performed under optimized conditions at 50 ° C for 3 hours (three replications), and then, for further purification, ethanol was re-precipitated. The structure of the extracted alginate was identified using 1hnmr and ft-ir spectroscopy. Then the values of manuronic to gluronic acid ratio (m / g), fgg, fmm and fgm (or fmg) blocks were calculated by 1hnmr spectroscopy as 0.89, 0.39, 0.33 and 0.14, respectively. Alginates of other species of Sargassum were compared. Intrinsic viscosity was also determined and a molecular mass of 7.026 105 105 g / mol was obtained. Sodium alginate was then extracted and detected and used to make an oral film. To prepare the film, a 1% solution (w / w) of sodium alginate was prepared and 1 g of glycerol was added as a plasticizer. The resulting solution was spread on Teflon plates and dried at 40 ° C for 48 hours. For comparison, films with the same formulation were prepared from industrial alginates and Sigma Aldrich and the physical and mechanical properties of the films were investigated. The prepared film showed lower water vapor passage speed, tensile strength and elongation to break point higher than the other two types of film. Also, the prepared films were immersed in 2% calcium chloride solution (mass / volume) for 5 minutes and their physical and mechanical properties were compared with its sodium alginate film. The results showed an improvement in the properties of the resulting film. Finally, the tg of the films was determined using the thermodynamic-mechanical thermal analysis test profiles.
