Effect of polyol plasticizers on properties and microstructure of soluble soybean polysaccharide edible films

Similar to most of the other films based on water-soluble natural polymers, pure soluble soybean polysaccharide (SSPS) films are rigid, fragile and brittle in nature, which make them difficult to process and limit their practical applications in food packaging. In this work, the effects of three commonly used polyol plasticizers, i. e. glycerol, sorbitol and polyethylene glycol 400 (PEG400), on properties of SSPS films were investigated. The SSPS films were prepared by solvent-casting and plasticized at three plasticizer concentrations (15 wt%, 30 wt% and 45 wt% based on SSPS). The addition of plasticizers significantly improved the ductility and water content of the SSPS films, thus overcoming the inherent brittleness of pure SSPS matrix. SSPS films plasticized with PEG400 exhibit the highest optical transparency, thermal stability and the lowest water solubility. Sorbitol-plasticized SSPS films show better tensile strength and water vapor barrier properties compared to other plasticized SSPS films. The use of glycerol as a plasticizer resulted in SSPS films with the highest elongation at break, moisture content and water solubility. X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy analyses suggested that the changed interactions between adjacent polysaccharide chains with the addition of various polyol plasticizers can be responsible for the observed changes in the properties of the SSPS films.