Effect of cold plasma treatment at different stages on the physicochemical properties and pork preservation of whey protein isolate-carboxymethyl chitosan composite films

This study aimed to investigate the impact of cold plasma (CP) treatment at different stages on the physicochemical properties of whey protein isolate (WPI)-carboxymethyl chitosan (CMCS) composite films and their application in pork preservation. CP treatment was implemented at three stages: before blending WPI with CMCS (WPI-CP-CMCS), after forming the WPI-CMCS composite (WPI-CMCS-CP), and following film drying (WPI-CMCS-H-CP). Results demonstrated that CP treatment influenced the film-forming solution by promoting WPI and CMCS aggregation, thereby increasing viscosity and viscoelasticity. The WPI-CMCS-CP film exhibited superior mechanical properties, achieving a tensile strength of 6.29 ± 0.11 MPa and an elongation at break of 21.34 ± 0.78 %, values significantly higher than those of WPI-CP-CMCS (5.24 ± 0.14 MPa, 7.98 ± 0.69 %) and WPI-CMCS-H-CP (4.72 ± 0.10 MPa, 10.21 ± 0.56 %) films. Microscopic imaging and intermolecular analysis revealed that CP enhanced molecular interactions, particularly by increasing disulfide bond formation in the WPI-CMCS-CP film. In pork preservation trials, CP-treated composite films delayed spoilage, inhibited microbial growth, stabilized pH, and reduced protein and lipid oxidation, with the WPI-CMCS-CP group showing the most pronounced effects. Overall, CP treatment significantly improved the performance of WPI-CMCS composite films, demonstrating their potential as sustainable, high-performance materials for food packaging applications. • The influence of CP at different stages on the film forming characteristics was investigated. • WPI-CMCS-CP films exhibited enhanced tensile strength and elongation at break. • CP is an effective method to develop WPI-CMCS composite films via promoting formation of disulfide bonds. • CP treated WPI-CMCS composite films exhibited excellent preserving function on the pork, particularly the WPI-CMCS-CP films.