Abstract: Soybean protein isolate (SPI) as a major ingredient was mixed with glycerol-based biopolyester prepared from modified glycerol to obtain SPI composite films, and changes in the mechanical properties, water content and glycerol migration rate of the resulting films during storage were monitored to investigate the effect of modified glycerol as a plasticizer on the film mechanical stability, water-holding capacity, glycerol migration stability and microstructure. The results showed that the composite films plasticized by a mixture of biopolyglycerol and fatty acid ratio (1:1, m/m) had the highest mechanical stability, and that of the tensile strength, extension at break, water vapor permeability coefficient, water content and glycerol migration rate increased by 18.08%, 34.52%, 14.68%, 17.02% and 74.28%, respectively, compared with the SPI films without unmodified glycerol. Moreover, the structure of the films plasticized by modified glycerol was more compact and continuous, forming a compact network on the surface. In conclusion, the incorporation of glycerol-based biopolyester could improve the mechanical stability of SPI composite films, which will provide the theoretical basis and technical support for broadening the application of SPI composite films.

Key words: soybean protein isolate (SPI), glycerol modification, glycerol-based biopolyester, mechanical stability, glycerol migration rate