The 30 W low-temperature plasma was used to scan the surface of the whey protein isolate-sodium caseinate-glycerol composite protein films for 0, 5, 10, 15 and 20 min. The effects of protein secondary structure, microscopic morphology, surface water-oil affinity, mechanical properties, barrier properties, thermal stability and sterilization ability of films were studied. The results showed that after plasma treatment for 5-10 min, the structure, the degree of α-helix and β-sheet in the secondary structure of the protein increased about 15%. In addition, the surface of the film became denser, rougher and showed less porous, and the glass transition temperature (Tg) rose to 150.60 ℃, decomposition temperature (Td) rose to 197.08 ℃. In terms of packaging performance, the tensile strength increased by 24.10%, the elongation at break decreased by 27.13% respectively. At the same time, the barrier properties of the film increased, and the oxygen transmission rate was reduced to 1.20 cm3/(m2·d), the water vapor transmission coefficient was reduced to 5.555×10-12 g·cm/(cm2·s·Pa), and the surface hydrophobicity and oleophobicity were significantly reduced due to their apparent changes (P<0.05). Besides, the light transmittance was reduced by 20%, and the water solubility was also slightly reduced. Good potential in the application of film sterilization treatment was showed that the total number of film colonies was reduced by about 93.93%. Therefore, plasma treatment with a lower energy rate could effectively improve the packaging characteristics of the film and the stability of the protein, enhance its surface roughness to facilitate the composite with other materials.
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