Inactivation kinetics of Salmonella typhimurium and Staphylococcus aureus in different media by dielectric barrier discharge non-thermal plasma

Authors: HUANG, MINGMING - Nanjing Agricultural University; Zhuang, Hong; WANG, JIAMEI - Hainan University; YAN, WENJING - Nanjing Agricultural University; ZHAO, JIANYING - Nanjing Agricultural University

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2018
Publication Date: 10/28/2018
Citation: Huang, M., Zhuang, H., Wang, J., Yan, W., Zhao, J. 2018. Inactivation kinetics of Salmonella typhimurium and Staphylococcus aureus in different media by dielectric barrier discharge non-thermal plasma. Applied Sciences. 8:2027.

Interpretive Summary: Microbiological quality and safety of food has been a challenge for food industry. Each year, millions of food products are lost as a result of microbiological spoilage and recalls. Dielectric barrier discharge-based non-thermal plasma (DBD-NTP) is a new non-thermal antimicrobial technique for inactivating foodborne pathogens and extending shelf life of fresh food products A number of studies have documented the efficacy of the DBD-NTP inactivation of microbes in food products. In this study, we investigated effects of DBD-NTP treatments on foodborne pathogens on either solid surface or in liquid media. Our data demonstrate that a DBD-NTP treatment can significantly reduce foodborne pathogen (Salmonella and Staphylococcus) populations regardless of medium. However, the pattern for the reduction varies with medium. On solid surface, DBD-NTP starts inactivating bacteria without delayed; however, a delay (about 60 sec) in killing is found when the pathogens are suspended in liquid media. DBD-NTP needs much longer time to kill foodborne pathogens in liquid media than on solid surfaces at the initial treatment. However, DBD-NTP treatments result in more reductions in pathogen populations in liquid media than on solid surfaces after bacteria were treated for more than 140 sec. Ion content and pH in liquid media can affect the antimicrobial efficacy of DBD-NTP treatments. These results demonstrate that DBD-NTP is more effective against foodborne pathogens on solid surfaces than in liquid media at the initial treatment; but it is more effective in liquid media than on solid surface for extended treatments.

Technical Abstract: A study was conducted to determine the effect of dielectric barrier discharge non-thermal plasma (DBD-NTP) on Salmonella typhimurium and Staphylococcus aureus populations on solid surfaces and in liquid suspensions. Our results showed that inactivation kinetics of S. typhimurium and S. aureus by DBD-NTP treatments can be well predicted with mathematical models. The survival curves of both S. typhimurium and S. aureus showed a log-linear phase followed by tailing behaviors on solid surfaces, and shoulder behaviors followed by a log-linear phase in liquid suspensions. The D values (decimal reduction time) for S. typhimurium and S. aureus in suspensions were higher than those on solid surfaces (p < 0.05). Additionally, the maxima of sublethal injury values under low NaCl concentration and neutral pH condition were higher than those under high NaCl and low pH condition. In addition, mathematical modeling was evaluated to predict the final inactivation result for potential industrial applications. This study indicates that different microbial supporting matrices significantly influence the inactivation effect of DBD-NTP; it also provides useful information for future applications of NTP in enhancing food shelf life and safety.