Thesis
EFFICACIES OF SANITIZERS AGAINST LISTERIA MONOCYTOGENES AND SPOILAGE FUNGI IN SIMULATED DUMP TANK WATER
Washington State University
Master of Science (MS), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000002418
Handle:
https://hdl.handle.net/2376/121880
Abstract
Listeria monocytogenes leads to foodborne outbreaks on fresh apples and apple products. Spoilage fungi such as Penicillium expansum cause blue mold in apples, leading to a large amount of food waste and economical loss. During commercial processing, harvested apples are first soaked in a dump tank and flume water system. To lower operational cost, the industry reuses water in dump tanks over several processing days, which leads to accumulations of microorganisms and organic matters. This practice increases potential risks of crosscontamination of the foodborne pathogens as well as spoilage microorganisms. To reduce the potential cross-contamination, the disinfectants such as chlorine or peroxyacetic acid are extensively used in dump tank water. However, little is known about the practical antimicrobial efficacy of these sanitizers used in dump tanks. This study evaluated antimicrobial efficacies of chlorine, peroxyacetic acid (PAA) against L. monocytogenes and spoilage fungi in simulated dump tank water (SDTW) at different levels of organic matters. Results showed that chlorine at v 25 ppm showed limited efficacy (~2.0-log10 CFU/ml after 5 min) against L. monocytogenes in SDTW regardless of organic matter levels. Anti-Listeria efficacy increased with increased concentrations and diminished by increased level of organic matters indicated by chemical oxygen demand (COD). Anti-Listeria efficacy of chlorine at 100 ppm was not significantly impacted at 1000 ppm COD but was reduced at 4000 ppm COD. Anti-Listeria efficacy of PAA increased with concentration and contact time, which was minimally influenced by the presence or level of organic matters. At 5 min and 4000 ppm COD, 40 ppm PAA resulted in over 8.0-log10 CFU/ml reduction of L. monocytogenes, which was higher than the 6.0-log10 CFU/ml caused by 100 ppm chlorine. However, compared to chlorine, PAA at maximum legal concentration, 80 ppm, had limited efficacy against spoilage fungi, leading to ~0.5-log10 CFU/ml after 5 min contact time. To improv
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Details
- Title
- EFFICACIES OF SANITIZERS AGAINST LISTERIA MONOCYTOGENES AND SPOILAGE FUNGI IN SIMULATED DUMP TANK WATER
- Creators
- Yuanhao Wang
- Contributors
- Meijun Zhu (Advisor)Thuy Bernhard (Committee Member)Dojin Ryu (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Agricultural, Human, and Natural Resource Sciences, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 110
- Identifiers
- 99900606753901842
- Language
- English
- Resource Type
- Thesis