In-package inhibition of E.coli 0157:H7 on bulk romaine lettuce using cold plasma

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

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2017
Publication Date: 1/30/2017
Citation: Min, S.C., Roh, S., Niemira, B.A., Boyd, G., Sites, J.E., Uknalis, J., Fan, X. 2017. In-package inhibition of E.coli 0157:H7 on bulk romaine lettuce using cold plasma. Food Microbiology. 65:1-6.

Interpretive Summary: Fresh produce can be contaminated by human pathogens such as Escherichia coli O157:H7. Cold plasma – a new type of sanitizing process - is a form of energized gas, which can be applied to fresh and fresh-cut fruits and vegetables. However, there is a need for treatments which can be used after the produce is already inside the package. A new type of cold plasma technology (DACP) was evaluated for the inactivation of Escherichia coli O157:H7, surface features, color, carbon dioxide generation, and weight loss of bulk Romaine lettuce in a commercial plastic clamshell container. The lettuce samples were packed in a model bulk packaging configuration (three rows with either 1, 3, 5, or 7 layers) in the container and treated with DACP. The DACP treatment reduced the number of E. coli O157:H7 in the leaf samples in the 1-, 3-, and 5-layer configurations by 60 – 85%, irrespective of where the leaves were in the stack. In the largest bulk stacking with 7 layers, a greater degree of reduction (92%) was observed at the top layer, but shaking the container increased the uniformity of the inhibition. DACP did not cause any sensory changes, such as surface features, color, respiration rate, or fresh weight of the samples, nor did these properties differ significantly according to their location in the bulk stack. DACP treatment inhibited E. coli O157:H7 on bulk lettuce in clamshell containers in a uniform manner, without affecting the physical and biological properties. This technology holds promise as a post-packaging process for fresh and fresh-cut fruits and vegetables that will reduce the risks of foodborne illness and improve food safety for consumers.

Technical Abstract: Dielectric barrier discharge atmospheric cold plasma (DACP) treatment was evaluated for the inactivation of Escherichia coli O157:H7, surface morphology, color, carbon dioxide generation, and weight loss of bulk Romaine lettuce in a commercial plastic clamshell container. The lettuce samples were packed in a model bulk packaging configuration (three rows with either 1, 3, 5, or 7 layers) in the container and treated by DACP (42.6 kV, 10 min). DACP treatment reduced the number of E. coli O157:H7 in the leaf samples in the 1-, 3-, and 5-layer configurations by 0.4 to 0.8 log CFU/g lettuce, with no significant correlation to the sample location (P > 0.05). In the largest bulk stacking with 7 layers, a greater degree of reduction (1.1 log CFU/g lettuce) was observed at the top layer, but shaking the container increased the uniformity of the inhibition. DACP did not significantly change the surface morphology, color, respiration rate, or weight loss of the samples, nor did these properties differ significantly according to their location in the bulk stack. DACP treatment inhibited E. coli O157:H7 on bulk lettuce in clamshell containers in a uniform manner, without affecting the physical and biological properties and thus holds promise as a post-packaging process for fresh and fresh-cut fruits and vegetables.