Summary of Awards to Date

A metagenomic approach to food safety risk mitigation in pears


Jan. 1, 2023 - Dec. 31, 2024

Amount Awarded



Laura Strawn, Ph.D.
Virginia Polytechnic Institute and State University


Faith Critzer, Ph.D., Hendrik C. den Bakker, Ph.D., Alexis M. Hamilton, Ph.D.


In 2014, the tree fruit industry faced its first outbreak of foodborne illness when fresh, intact apples were linked to a multistate listeriosis outbreak due to caramel-coated apple consumption. Since then, industry and food safety experts have continually worked to better understand how this outbreak occurred, the conditions that might have impacted its likelihood, and how to prevent this from occurring in other commodities with similar production, storage, and packing practices. Much emphasis has been placed on the storage and packing environment since fresh, intact tree fruit consumed as ready-to-eat products can be stored for up to one year before consumed. To help inform and better prepare the pear industry, we have designed a series of experiments to better understand 1) the pear surface microbiome before storage, 2) how the storage environment impacts the microbiome of marketable and unmarketable pears, and 3) how key players in the microbiome can impact food safety risks throughout pear storage. We will share our findings with the industry through presentations to stakeholders, articles for grower and packer audiences, and peer-reviewed scientific literature.

Technical Abstract

The 2014 listeriosis outbreak linked to caramel apples demonstrated the potential for whole, intact tree fruit to carry contamination through to the consumer. While existing research since has evaluated potential conditions that could support the growth of foodborne pathogens on fruit surfaces, this work has primarily been focused on whole, intact fresh apples, leaving the pear industry vulnerable to opportunities for contamination and a lack of science-backed recommendations to prevent contamination or control microbial growth under industry-relevant conditions. Research that does exist to support the long-term storage of fresh pears emphasizes quality considerations only and does not take into account how this could impact food safety risks over time. The proposed research will seek to i) identify culturable microbiological community members (yeasts, molds, and lactic acid bacteria) on conventional, whole, intact pears prior to storage; ii) describe yeasts, molds, and lactic acid bacteria composition of marketable and unmarketable conventional, whole, intact pears under two different storage practices at three, six, and nine months in long-term controlled atmosphere cold storage to develop a metagenomic profile and track community composition; and iii) co-inoculate representative yeast, mold, and bacterial community members with Listeria monocytogenes under industry-relevant conditions to characterize synergistic and antagonistic effects; all on fresh pears (Green Anjou). Lastly, our team will also determine how the most prevalent bacterial, yeast, and mold isolates from the microbiome during storage impact the growth and survival of Listeria monocytogenes on intact and wounded fruit. Results from these studies will yield data for the fresh pear industry on metagenomic profiles of marketable and unmarketable pears. This information can direct existing and future management practices to optimize the quality and food safety of pears simultaneously. We will use every opportunity to communicate our research and findings to stakeholders throughout the project through presentations, open access peer-reviewed literature, and publications which target pear growers and packers. Effective communication of our research findings will guide postharvest handling practices that will minimize the likelihood of outbreaks and preserve the long-term quality of fresh pears during storage.