Effect of dielectric barrier discharge on microorganism inactivation and quality of orange juice

In order to eliminate some unwanted side-effects caused by thermal processes sterilization, non-thermal sterilization techniques have been rapidly developed in recent years. The low temperature plasma (LTP) generated by parallel-plate electrode DBD was employed to sterilize three kinds of microorganisms inoculated with and without orange juice, and its influence on quality of orange juice was investigated. Three kinds of typical microorganisms, Staphylococcus aureus (gram-positive), Escherichia coli (gram-negative), and Candida albicans(typical of fungi), were employed to explore the inactivation mechanisms. The effect of LTP on microorganism inactivation with different treatment time was investigated. In addition, the effect of LTP on shelf life of orange juice was studied, and the biological and medical detection methods and instruments (4-dinitrophenylhydrazine colorimetry, sodium hydroxide titration, Abbe refractometer, acidometer and spectrophotometer) were employed to measure the Vit C concentration, total acid, °Brix, pH value and turbidity in orange juice before and after plasma treatment, also the effect of pH value on microorganism inactivation was investigated. The experimental results show that: low temperature plasma is safe and effective in inactivating microorganisms (Staphylococcus aureus, Escherichia coli, and Candida albicans) in orange juice, and can significantly extend its shelf life. LTP treatment has hardly effect on nutritional, physical and chemical characteristics of the orange juice. The pH value does not play an important role in microorganism inactivation. It is proposed that microorganism inactivation is mainly due to reactive oxygen species (ROS) and charged particles.