Control of pathogenic bacteria on the surface of rolling fruits by an atmospheric pressure air dielectric barrier discharge system

Atmospheric pressure cold plasma technology has great application potential in the field of food safety. A novel atmospheric air dielectric barrier discharge device has been designed to generate plasma directly on the surface of spherical fruit. This device consists of the quartz tube, the high-voltage electrode attached to the outer wall of the quartz tube, and the fruit placed onto the inner surface of the quartz tube, acting as the ground electrode. The intensified charge-coupled detector images show that a uniformly scanning discharge channel is formed between the surface of treated substance and the inner wall of quartz tube. When the treated substance is rolled in the device, the uniform plasma is directly formed over the fruit surface. The bactericidal efficiency of plasma against pathogenic microorganisms on rolling fruit surface has been studied. The number of Staphylococcus aureus (S. aureus) on the surface of fruit treated by plasma for 15 s in rolling state is 1.57 log10 CFU less than that of the static state. Compared with the initial bacterial concentration, the number of S. aureus on the surface of 1 cm2 decreases by 5.9 log10 CFU after plasma treatment of rolling fruit for 15 s. In conclusion, the fruit surface is uniformly treated by the novel plasma device and S. aureus on the fruit surface was sterilized without causing thermal damage to the fruit surface.