Abstract:With the increasing demands of modern life on the environment，the preparation of packaging film using natural biopolymers（such as polysaccharides and proteins）instead of petroleum-based materials has attracted more attention.However，the poor mechanical properties restricted the application of protein-based films.In this paper，casein powder was modified by dielectric barrier discharge cold plasma（DBD-CP），and the structure and properties of casein film were investigated.After group assignment with treatment voltage and treatment time as variables，changes in microstructure，functional groups，secondary structure，and crystal structure of casein before and after DBD-CP modification were analyzed，and meanwhile，the physical properties of the modified casein film were also studied.It was found that after DBD-CP treatment，casein showed rough molecular surface and smaller size，and the secondary structure of casein films also was changed via DBD-CP treatment with the time and voltage.Moreover，the thermal stability and ultimate tensile elongation of the modified casein increased significantly（p＜0.05）.