You may have heard about the recalls for products like lettuce, spinach, or other leafy greens. These widely consumed vegetables are among the leading causes of foodborne illness, affecting thousands each year. Leafy greens can be contaminated with harmful E. coli or other bacteria from soil splashes or contaminated irrigation water during field growth or through handling and processing. While growers and processors implement various safety protocols, some contaminated items still end up in the hands of consumers.
A recent study from the University of Illinois Urbana-Champaign examines control measures and testing practices within the produce supply chain, aiming to identify the most effective risk management strategies across different scenarios.
“The objective of this project is to provide the produce industry with a tool to estimate microbial risks and support food safety decision-making. We created a model framework and demonstrated its use by simulating a case study for leafy greens. This allowed us to assess various food safety practices and their trade-offs,” explained lead author Gabriella Pinto, a doctoral student in the Department of Food Science and Human Nutrition, part of the College of Agricultural, Consumer and Environmental Sciences at Illinois.
Co-author Gustavo Reyes pointed out that while other risk assessment tools exist, they are designed for specific purposes. Reyes was a graduate student in FSHN during the research and is now a food safety manager for Western Growers Association.
“This model is adaptable, enabling users to simulate different systems and potential microorganisms impacting the produce environment while evaluating various interventions. The results can help enhance risk management strategies,” Reyes noted.
The model framework consists of five stages: primary production, harvesting, processing, retail, and consumer handling. At any of these stages, users can estimate contamination chances, modify contamination levels, or incorporate product testing. The output measures the risk of a product testing positive for microbial contamination when it reaches consumers.
“Leafy greens were chosen as a test case due to their frequent association with outbreaks and recalls. The produce industry is continually seeking to understand the causes of these incidents. Furthermore, the practices we analyze can apply to many different types of commodities,” Pinto remarked.
Leafy greens like fresh-cut lettuce typically undergo a washing process using food-safe acid to minimize microbial contamination. Processors can mitigate risk by enhancing these process controls or by implementing final product testing to avoid sending contaminated items to consumers.
“We aimed to compare these two strategies to determine which is more effective at managing risk in different contamination scenarios,” Pinto said.
The researchers discovered that improving process controls (like washing) significantly lowers the likelihood of a positive test result at retail (which suggests less risk of a recall) compared to merely conducting additional product testing at the end of processing. They concluded that, while end-stage product testing does help reduce public health threats and recall risks, it often leads to the rejection of many lower-risk batches. If contamination is found, the entire batch is discarded, but significant contamination events that prompt both recalls and public health issues are infrequent.
“The model doesn’t specify the exact microbial reduction you would achieve with these strategies, but it allows for relative comparisons that can guide management choices, which is extremely valuable for the industry. Our findings aid growers and processors in focusing their resources where they can make the most impactful changes,” Reyes stated.
The researchers have also developed an interactive webpage, SCRM-Lite, which allows users to explore the published contamination scenarios and intervention strategies from the test case.
“Food production mostly takes place outdoors in open systems influenced by nature, so a completely contamination-free food system is unattainable. Efforts continue both to prevent contamination and to create processing methods that reduce it,” said Matt Stasiewicz, associate professor in FSHN and corresponding author of the paper.
“We’ll likely never find a perfect method that sterilizes every item, so we must develop a variety of options and determine which practices are most effective. Much of my lab’s work centers on risk management, improved decision-making, and utilizing modern computation for risk modeling.”
The study titled “Development of a flexible produce supply chain food safety risk model: Comparing tradeoffs between improved process controls and additional product testing for leafy greens as a test case,” is published in the Journal of Food Protection [DOI:10.1016/j.jfp.2024.100393]. The research was funded by The Center for Produce Safety project 2023CPS08.
