Effects of different saccharides glycosylation modified soy protein isolate on its structure and film-forming characteristics

With the serious impact of traditional plastic packaging on the environment, the development of safe, environmentally friendly and degradable packaging materials has become a research hotspot. Glycosylation reaction has been explored by researchers because of its green, efficient and simple. In this study, the film-forming properties of soy protein isolate (SPI) were improved by glycosylation modification. Different types of saccharides (monosaccharides: glucose, fructose, xylose; oligosaccharides: maltose, fructooligosaccharide, xylooligosaccharide; polysaccharide: gum arabic) were introduced into the SPI by moist heat method. The results show that the xylose-modified SPI film has the best performance in mechanical properties and thermal stability, and its tensile strength is increased to 5.1 MPa, and its elongation reached 117.8 %. Structural analysis revealed that glycosylation resulted in a decrease in α-helix content of SPI, while β-sheets and random coils increased, forming a tighter cross-linked network, improving film density and stability. Furthermore, xylose modification significantly reduced the water vapor transmission rate to only 12.64 g/m²·24 h. These modifications significantly enhance the comprehensive properties of SPI films, especially in terms of thermal stability and moisture barrier properties. The correlation analysis between SPI film properties and internal structure shows that glycosylation can change the internal structure of protein and further affect the film properties. The research in this paper provides a theoretical basis for the glycosylation modification of SPI, and provides a new idea for the sustainable development of food packaging materials.