Thermodynamic analysis as a useful tool to study the physical properties of sweet‐potato starch films reinforced with alginate microparticles

Abstract Thermodynamic analysis is a useful instrument for understanding the state of adsorbed water molecules and their influence on the physical and chemical stability of packaging materials during their functioning. This study assesses the effect of alginate microparticles as reinforcement on the water‐adsorption characteristics and physical properties of sweet‐potato starch biopolymer films. Glycerol was utilized as plasticizer. Then, physical stability was evaluated through minimum integral entropy criteria. The incorporation of alginate microparticles significantly decreased (p < 0.05) spin–lattice relaxation times, water‐vapor permeability, and the films' water solubility. Additionally, the adsorption capacity, as well as the physical stability of the films, were increased from 0.38 to 0.63 water activity at 25°C. An antiplasticization effect of water was noted in the water‐activity range, where the adsorption process was entropy‐controlled. Maximal resistance to breakage was enhanced in the minimum integral‐entropy zone. SEM micrographs revealed a rougher surface of reinforced films. Therefore, it is feasible to anticipate the most appropriate water activity where best film performance is achieved, employing minimum integral‐entropy criteria.