Fresh produce may be contaminated by bacterial pathogens including Listeria monocytogenes during harvesting, packaging, or transporting. Consumers may be at risk of foodborne illness if produce become contaminated. In this project, a cavitation process (formation of bubbles in water) was studied to determine the efficacy of microbubbles at inactivating the pathogen L. monocytogenes on stainless steel and the surface of fresh cucumber and avocado. Stainless steel coupons (1"×2''), cucumber, and avocado surfaces were inoculated with L. monocytogenes (LCDC strain). After 1, 24 or 48 h, loosely attached cells were washed off, and inoculated areas were targeted by microbubbles (~0.5 mm dia.) through an air stone (1.0 L air/min) for 1, 2, 5, or 10 min. After treatment, samples were transferred to sterile containers and serial diluted in peptone water and plated on Oxford agar. Plates were incubated for 48 h at 35℃. For stainless steel, the mean log reduction of L. monocytogenes (48 h drying) peaked at 2.95 after 10 min of microbubbles when compared to a no bubble treatment. After 48 h pathogen drying, cucumbers treated for 10 min resulted in a 1.78 mean log reduction of L. monocytogenes. For avocados, the mean log reduction of L. monocytogenes (24 hr drying) peaked at 1.65 after 10 min of microbubbles. This cavitation treatment (10 mins) reduced over 95% of L. monocytogenes on the surface of stainless steel, cucumber, and avocado. Microbubble applications may be an effective, economical, and environmental-friendly way to remove L. monocytogenes and possibly other bacterial pathogens from food impact surfaces and the surface of whole, intact fresh produce. / Master of Science in Life Sciences / Fresh produce may be contaminated by bacterial pathogens like Listeria monocytogenes during the process of harvesting, packaging, or transport. Consuming contaminated fresh produce without enough and proper decontaminated measures, consumers are in risk of being infected with foodborne illness. A cavitation process (formation of bubbles in water) was conducted to determine the efficacy of microbubbles at inactivating the pathogen Listeria monocytogenes on the impact surface of fresh produce (stainless steel), fresh cucumber, and fresh avocado.
Stainless steel coupons (1"×2''), fresh cucumbers, and fresh avocados were inoculated respectively with Listeria monocytogenes (LCDC strain). After removing loosely attached pathogen cells on the surface of inoculated steel coupons, cucumbers, and avocados, their inoculated areas were targeted by microbubbles (~0.5 mm dia.) for 1, 2, or 10 minutes, with a constant air flow rate of 1.0 L/min through an air stone.
The L. monocytogenes on stainless steel and cucumber, and avocado surfaces was reduced by 95% to 99%. This study suggests that microbubbles may remove, and possibly inactivate, L. monocytogenes effectively from the surface of fresh produce and their impact surfaces. Microbubbles thus could be an effective, economical, and environmental-friendly tool for minimizing produce contamination.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/107688 |
| Date | 16 January 2022 |
| Creators | Chen, Pengyu |
| Contributors | Food Science and Technology, Eifert, Joseph D., Strawn, Laura K., Jung, Sunghwan |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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