Author
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Niemira, Brendan |
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Boyd, Glenn |
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Sites, Joseph |
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Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/13/2014 Publication Date: 5/2/2014 Citation: Niemira, B.A., Boyd, G., Sites, J.E. 2014. Cold plasma rapid decontamination of food contact surfaces contaminated with Salmonella biofilms. Journal of Food Science. 79(5):M917-M922. Interpretive Summary: Pathogens like Salmonella can persist in protected niches in food in processing environments. Cross-contamination of fresh produce and other foods from these pathogen reservoirs is a known risk factor. Industry requires a rapid, waterless, zero-contact, chemical-free method for removing pathogens from food-contact surfaces. Cold plasma (a type of energized gas) was tested for its ability to inactivate firmly attached cultures of Salmonella on a test surface (glass slides). These slides were placed on a conveyor belt and passed under a cold plasma emitter at various line speeds to provide exposure times of 5, 10 or 15 seconds. The test plate was positioned either 5 cm or 7.5 cm under a plasma jet emitter. The cold plasma was generated at one atmosphere using filtered air as the feed gas. The frequency of high voltage electricity used for the cold plasma was varied from 23 kHz to 48 kHz. At the closer spacing (5 cm), Salmonella recovered from cold plasma treated biofilms was reduced by up to 97%, (5 seconds), 98% (10 seconds) and 99.3% (15 seconds). Increasing the distance to 7.5 cm generally reduced the efficacy of the 15 second treatment, but had a variable effect on the 5 and 10 second treatments. Variation of the high voltage electricity had a greater effect on 10 and 15 second treatments, particularly at the 7.5 cm spacing. For each combination of time, distance and frequency, the firmly attached Salmonella cultures all responded to cold plasma treatment in a manner consistent with each other, regardless of how long those cultures had been grown. The results show that cold plasma quickly and effectively inactivated a firmly attached form of Salmonella contamination on a model food contact surface. This suggests that cold plasma is a possible tool for rapid disinfection of hard-to-sanitize materials associated with food processing. Technical Abstract: Cross-contamination of fresh produce and other foods from persistent pathogen reservoirs is a known risk factor in processing environments. Industry requires a rapid, waterless, zero-contact, chemical-free method for removing pathogens from food-contact surfaces. Cold plasma was tested for its ability to inactivate Salmonella biofilms. A three-strain Salmonella cocktail culture was allowed to form adherent biofilms for 24, 48 or 72 hours on a test surface (glass slides). These were placed on a conveyor belt and passed at various line speeds to provide exposure times of 5, 10 or 15 s. The test plate was either 5 cm or 7.5 cm under a plasma jet emitter operating at one atmosphere using filtered air as the feed gas. The frequency of high voltage electricity used for cold plasma generation was varied from 23 kHz to 48 kHz. At the closer spacing (5 cm), cold plasma reduced Salmonella biofilms by up to 1.57 log cfu/ml (5 s), 1.82 log cfu/ml (10 s) and 2.13 log cfu/ml (15 s). Increasing the distance to 7.5 cm generally reduced the efficacy of the 15 s treatment, but had a variable effect on the 5 and 10 s treatments. Variation of the high voltage electricity had a greater effect on 10 and 15 s treatments, particularly at the 7.5 cm spacing. For each combination of time, distance and frequency, Salmonella biofilms of 24, 48 and 72 hours growth all responded to cold plasma treatment in a manner consistent with each other. The results show that cold plasma quickly and effectively inactivated a durable form of Salmonella contamination on a model food contact surface, suggesting this technology as a possible tool for rapid disinfection of materials associated with food processing. |
