Microbial safety and quality attributes of milk following treatment with atmospheric pressure encapsulated dielectric barrier discharge plasma

Abstract

This study evaluated the microbial and physicochemical characteristics of milk that was treated with encapsulated dielectric barrier discharge (DBD) plasma. Encapsulated DBD plasma was generated in a plastic container (250 W, 15 kHz, ambient air) and DBD plasma treatment was applied to milk samples for periods of 5 and 10 min. The total aerobic bacterial count in the untreated control sample was 0.98 log CFU/mL. Following plasma treatment, no viable cells were detected in the milk samples. When milk samples were inoculated with Escherichia coli, Listeria monocytogenes, and Salmonella Typhimurium, plasma treatment for 10 min resulted in a reduction in bacterial counts by approximately 2.40 log CFU/mL. The pH of the sample milk was found to decrease after the 10-min plasma treatment. Hunter color La and b* values of milk increased, and the a* value decreased as a result of the plasma treatment. The production of 2-thiobarbituric acid reactive substances increased slightly, but not significantly, following plasma treatment. The results of this study indicate that encapsulated DBD plasma treatment for less than 10 min improved the microbial quality of milk with slight changes in physicochemical quality of milk. (C) 2014 Elsevier Ltd. All rights reserved.