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Research Project: Monitoring and Molecular Characterization of Antimicrobial Resistance in Foodborne Bacteria

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Title: Analyzing aggregate environmental monitoring data for Listeria spp. in frozen food manufacturing environments

item MAGDOVITZ, BRITTANY - University Of Georgia
item GUMMALLA, SANJAY - American Frozen Food Institute
item GARREN, DONNA - American Frozen Food Institute
item THIPPAREDDI, HARSHAVARDHAN - University Of Georgia
item Berrang, Mark
item HARRISON, MARK - University Of Georgia

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2021
Publication Date: 1/1/2022
Publication URL:
Citation: Magdovitz, B., Gummalla, S., Garren, D., Thippareddi, H., Berrang, M.E., Harrison, M.A. 2022. Analyzing aggregate environmental monitoring data for Listeria spp. in frozen food manufacturing environments. Food Control.

Interpretive Summary: Listeria monocytogenes is an ubiquitous human pathogen that can be present in food processing plants and survive cold temperatures. As such it represents a potential cross contamination threat for frozen foods during processing. By using a double blind anonymous system, we collected Listeria sampling data; 42,799 data points from 27 frozen food processing plants. These data show that sample sites most distal from food contact surfaces were most likely to be contaminated. Samples were more likely to be positive both before and after any heat treatment processing step and cold storage areas of processing plants were especially problematic. These data are complied in such a way as to provide information to processors that will proof useful in designing the most effective routine sampling plans in an effort to detect and control this deadly pathogen in processing plants that produce frozen foods.

Technical Abstract: Food processors face serious challenges due to the ubiquity and prevalence of Listeria monocytogenes in production and processing facilities. Environmental monitoring for Listeria within the industry is important and detection of Listeria spp. is often used as an indicator for the potential presence of L. monocytogenes in the food processing environment. Environmental monitoring data from the frozen food manufacturing industry was compiled and analyzed to evaluate the adequacy of current practices in mitigating risks of L. monocytogenes in the processing environment and to determine if there are trends that could be used to further refine industry practices. A method to collect anonymous data for analysis to build a strong aggregate data set from multiple facilities was used. Information included general descriptions of each facility and specific information about individual environmental monitoring test results from zones 2-4, nonfood contact surfaces. Information collected from facilities included the size of the facilities and how environmental monitoring samples were collected and analyzed. For each individual sample, information collected included the area or equipment sampled and the result of sampling. Descriptors were provided to allow for grouping of similar results. The data represents environmental monitoring samples that were collected between six months to a year prior to the beginning of this research. Twenty-seven facilities provided 42,799 environmental monitoring observations. Zones 3 and 4 had a higher probability of Listeria positive results compared to zone two for routine environmental monitoring samples (p<0.05). Pre-lethality and post-lethality production areas had a higher probability of Listeria positive results compared to lethality areas for all environmental samples (p<0.05). Cold storage locations, i.e., coolers and freezers had a significantly higher probability for a Listeria positive result than noncold storage areas (p<0.01). Aggregate prevalence data from processing operations across the industry can provide information for guidance on focusing sanitation within processing operations to reduce risk related to L. monocytogenes. These data helps to identify common themes in the industry and determine potential areas on which to focus when testing for prevalence of Listeria spp. within the food processing environment. This study serves as a useful baseline for continued improvement in environmental monitoring across all frozen food manufacturing facilities.