Effect of atmospheric cold plasma treatment on structural, thermal, and mechanical properties of pea protein isolate edible films

The current study has been undertaken to examine the influence of atmospheric cold plasma (ACP) treatment on the thermo-mechanical, structural, and barrier properties of pea protein isolate (PPI) edible films. ACP treatment was applied to the PPI films for selected exposure times (30, 60, 90, and 120 s) at a fixed voltage of 20 kV. The ACP treatment increased the surface hydrophobicity of the films considerably, from 38.43 ± 3.32° to 61.67 ± 2.06°, demonstrating the unfolding of hydrophobic protein groups due to surface etching. The effect was further pronounced with the reduced protein aggregates and improved compactness in the surface microstructure. FTIR and XRD results demonstrated ACP-induced modifications in the secondary protein structures, including the transformation of α-helix into β-sheet structures. The DSC protein denaturation temperature increased from 61.16 °C to 72.56 °C after 30 s of ACP treatment, suggesting cross-linking on the PPI surface. After 120 s of ACP treatment, the tensile strength increased from 2.40 ± 0.08 to 3.98 ± 0.15 MPa, and elongation at break increased from 77.53 ± 1.26 to 106.95 ± 2.70%. Additionally, the water vapor transmission rate decreased from 2.32 ± 0.13 to 1.80 ± 0.03 g/h.m2. Furthermore, the treatment also enhanced the biodegradation process of PPI films. Overall, the ACP treatment appears to be a successful structural modification technique for plant-based edible films with improved packaging properties.