Title: Inactivation of L. innocua, S. Typhimurium, and E. coli O157:H7 on surface and stem scar areas of tomatoes using in-package ozonation Authors
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 21, 2012
Publication Date: September 4, 2012
Citation: Fan, X., Sokorai, K.J., Engemann, J., Gurtler, J., Liu, Y. 2012. Inactivation of L. innocua, S. Typhimurium, and E. coli O157:H7 on surface and stem scar areas of tomatoes using in-package ozonation. Journal of Food Protection. 75:1611-1618. Interpretive Summary: Many recent outbreaks of foodborne illnesses are associated with consumption of raw fresh fruits and vegetables. Effective decontamination technologies are needed to safeguard our food supply. This study was conducted to investigate the effectiveness of a novel in-packaging ozonation technology in inactivating Listeria innocua, Salmonella Typhimurum and Escherichia coli O157:H7 on tomato fruit. Results showed that high ozone concentration was produced inside the packages containing tomatoes, and the ozonation system reduced the population of the three bacteria without damaging the color or texture of tomatoes. Therefore, the system has a potential to be used by the produce industry to enhance microbial safety of tomatoes.
Technical Abstract: A novel in-package ozonation device (PlasmaLabel) was evaluated for its effectiveness in inactivating three microorganisms, such as Listeria innocua, attenuated Salmonella Typhimurium, and Escherichia coli O157:H7 on tomatoes, and its effect on fruit quality. The PlasmaLabel system produced ozone inside sealed film bags, reaching a concentration of 1,000 ppm within 1 min of activation. The three bacterial cultures were inoculated either on the smooth surface of the tomatoes or the stem scar areas before being sealed in plastic film bags and subjected to treatment using the PlasmaLabel system. When L. innocua was inoculated onto the smooth surface of the fruit, the bacterium was reduced to non-detectable level within 40 sec of treatment and was reduced by 4 log CFU/fruit on the stem scar area. Increase in treatment time did not result in a proportionally increase in bacterial reduction. For E. coli O157:H7 and Salmonella, there was little difference (less than 1 log) in the effectiveness of the system between surface and scar inoculated bacteria. Both bacteria were typically reduced by 2-3 log CFU/fruit after 2-3 min treatment. During a 22-day post-treatment storage of PlasmaLabel-treated tomatoes, no negative effect on fruit color and texture was observed. The results suggest that the three bacteria responded differently to ozonation, and the PlasmaLabel system may be an alternative to aqueous sanitizers for inactivating foodborne pathogens on tomatoes.