In-Package atmospheric cold plasma treatment of bulk grape tomatoes for their microbiological safety and preservation

Authors: MIN, SEA - Seoul Women'S University; ROH, SI HYEON - Seoul Women'S University; Niemira, Brendan; Boyd, Glenn; Sites, Joseph; Fan, Xuetong; Sokorai, Kimberly; Jin, Zhonglin

Submitted to: Food Research International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2018
Publication Date: 4/10/2018
Citation: Min, S.C., Roh, S., Niemira, B.A., Boyd, G., Sites, J.E., Fan, X., Sokorai, K.J., Jin, Z.T. 2018. In-Package atmospheric cold plasma treatment of bulk grape tomatoes for their microbiological safety and preservation. 108:378-386.

Interpretive Summary: Cold plasma is a form of ionized gas which can inactivate human pathogens on fresh and fresh-cut fruits and vegetables. In this study, the effects of dielectric barrier discharge atmospheric cold plasma (DACP) treatment on the inactivation of Salmonella and the storability of grape tomato were investigated. Grape tomatoes, with or without inoculation with Salmonella, were packaged in a clear plastic (polyethylene terephthalate, PET) commercial clamshell container, as individual tomatoes or in groups of tomatoes piled atop each other. The tomatoes were cold plasma-treated at 35 kV at 1.1 A for 3 min using a DACP system. This cold plasma system is equipped with a pin-type high-voltage electrode. DACP treatment significantly inactivated Salmonella without altering the color or firmness of the grape tomatoes. DACP treatment inactivated Salmonella uniformly in both layers of the double-layer configuration of the grape tomatoes regardless of the position of the tomatoes in each layer. Salmonella was most efficiently inactivated when the headspace to tomato volume ratio of the container was highest. Integration of rolling of tomatoes during treatment significantly increased the Salmonella reduction rates from 87% to 99.9% in the double-layer configuration of the tomato samples. Moving the container during treatment also initially reduced the number of total mesophilic aerobic bacteria and yeast and molds in the double-layer configuration of tomato samples by 95% and 96.8%, respectively. The cold plasma treatment effectively suppressed the growth of Salmonella and indigenous microorganisms at 10 and 25 degrees C, and did not cause any changes to the surface color, firmness, weight loss, lycopene concentration and residual ascorbic acid of grape tomatoes during storage at 10 and 25 degrees C. The DACP form of cold plasma treatment holds promise as a post-packaging process for improving microbial safety against Salmonella and storability of fresh grape tomatoes.

Technical Abstract: Effects of dielectric barrier discharge atmospheric cold plasma (DACP) treatment on the inactivation of Salmonella and the storability of grape tomato were investigated. Grape tomatoes, with or without inoculation with Salmonella, were packaged in a polyethylene terephthalate (PET) commercial clamshell container and cold plasma-treated at 35 kV at 1.1 A for 3 min using a DACP system equipped with a pin-type high-voltage electrode. DACP treatment inactivated Salmonella (p < 0.05) without altering the color or firmness of the grape tomatoes (p > 0.05). DACP treatment inactivated Salmonella uniformly in both layers of the double-layer configuration of the grape tomatoes regardless of the position of the tomatoes in each layer. Salmonella was most efficiently inactivated when the headspace to tomato volume ratio of the container was highest. Integration of rolling of tomatoes during treatment significantly increased the Salmonella reduction rates from 0.9 ± 0.2 log CFU/tomato to 3.3 ± 0.5 log CFU/tomato in the double-layer configuration of the tomato samples. Rolling-integrated DACP also initially reduced the number of total mesophilic aerobic bacteria and yeast and molds in the double-layer configuration of tomato samples by 1.3 ± 0.3 and 1.5 ± 0.2 log CFU/tomato, respectively. DACP treatment effectively suppressed the growth of Salmonella and indigenous microorganisms at 10 and 25 deg C, and did not influence the surface color, firmness, weight loss, lycopene concentration and residual ascorbic acid of grape tomatoes during storage at 10 and 25 deg C. DACP treatment holds promise as a post-packaging process for improving microbial safety against Salmonella and storability of fresh grape tomatoes.