Film-forming modifications and mechanistic studies of soybean protein isolate by glycerol plasticization and thermal denaturation: A molecular interaction perspective

[Display omitted] •Hydrogen bonds and van der Waals forces were occurred between glycerol and SPI.•Glycerol combined with basic amino acids interfered interactions between proteins.•Glycerol has an effect on the formation of inter-subunit disulfide bonds.•Heat denaturation resulted in a more uniform distribution of protein particle size.•Thermal denaturation enhanced the light barrier and mechanical properties of films. Plasticizer and thermal denaturation are indeed important factors for soybean protein film formation. The objective of the study was to investigate the effects of glycerol and thermal denaturation on the film-forming performances of soybean protein isolate (SPI) and elucidate the underlying mechanisms. From the results, glycerol had almost no effect on the protein’s secondary and tertiary structures. Indeed, the dispersion of glycerol diminished the intra- or intermolecular hydrogen bonding of SPI and interacted with the amino acids of subunits through hydrogen bonding and van der Waals forces. By interfering with protein network interactions, the glycerol molecule achieved a plasticizing effect on SPI films. The effects of heat treatment on SPI film properties were mainly realized through the changes in molecular conformation caused by protein denaturation, which manifested in the enhancement of light barrier and mechanical capabilities, and markedly altered the distribution of water states within the film network. This study provided valuable insights to clarify the mechanism of protein film formation.