Cold plasma-assisted transglutaminase cross-linking: Effects on the structure and film-forming properties of soybean protein fractions

To investigate the impact of cold plasma (CP) and transglutaminase (TGase) on the structural and physicochemical properties of soybean protein fraction solutions and films, dynamic monitoring was performed at different stages during the preparation of film-forming solution. The study focused on key parameters including surface hydrophobicity, particle size, intrinsic fluorescence, and sulfhydryl content. The results showed that both different durations (1, 2, 3, 4 and 5 min) of CP treatment and TGase cross-linking significantly affected the interfacial properties and intermolecular interactions of the proteins. With the increase in CP treatment time, the cross-linking degree and protein interaction of the films were significantly enhanced. Additionally, the improved order of protein secondary structure, water barrier and mechanical properties indicated the feasibility and effectiveness of CP-assisted TGase cross-linking of proteins, especially the film sample treated with CP for 3 min showed higher mechanical strength (from 7.71 MPa to 9.00 MPa) and lower water vapor permeability (from 4.77 × 10⁻¹⁰ g Pa⁻¹s⁻¹m⁻¹ to 3.97 × 10⁻¹⁰ g Pa⁻¹s⁻¹m⁻¹) (p < 0.05). This research provides new insights into the application of CP technology in environmentally friendly packaging films.