Unseen guardrails: How producers protect your food before it reaches the grocery store
Food safety scientists in the University of Arizona's College of Agriculture, Life and Environmental Sciences are working to ensure that food grown, processed and eaten in the United States is as safe as it can be. Their research into areas like agricultural water quality, pathogen genomics and epidemiology, detection methods, and antimicrobial treatments informs health and safety standards for producers in Arizona and beyond. They work shoulder-to-shoulder with growers and regulators to bring that research into the field so we can trust in the safety of our food.
Every time we buy fresh produce or order a burger at a restaurant, we’re participating in a massive system of trust. While highly publicized food recalls and outbreaks of foodborne illness can raise concerns among consumers, rigorous safety measures and quality controls are built into our food system at every level, beginning with food producers. They play an essential role in the strictly structured, scientifically robust and largely invisible defensive shield that operates long before food ever reaches a grocery store or restaurant kitchen.
We talked with three food safety experts from the College of Agriculture, Life and Environmental Sciences to learn how scientists work with producers and regulators to keep our food system as safe as possible.
Where do foodborne pathogens come from, and how do they get into the growing environment?
According to Sadhana Ravishankar, a professor in the School of Animal and Comparative Biomedical Sciences and chair of the University of Arizona Food Safety Consortium, many common pathogens found in food originate in the intestinal tracts of animals and humans. That’s why careful handling of animal-derived products like meat, dairy and eggs is crucial.
“With meat and poultry, preventing contamination is very difficult because the enteric pathogens like Salmonella and E. coli O157:H7 are already there,” she said. “Food safety measures like sanitizing tools, prompt chilling, and use of pasteurization and decontamination washes mitigate these risks.”
According to the research, contamination from animal and human waste is also how many pathogens reach the growing environment for produce. Since most crops are grown outdoors, they are exposed to potential vectors like agricultural water, wildlife and nearby livestock, soil and blowing dust, field inputs like fertilizers and compost, and human contact.
“In general, water tends to be the major vector for transporting waste from one location to another,” said Channah Rock, a professor in the Department of Environmental Sciences who specializes in fresh produce safety. “I’d place wildlife second, since you have birds flying overhead and wildlife that might venture into fields in search of water or a place to sleep.”
How do producers prevent contamination?
As the saying goes, “An ounce of prevention is worth a pound of cure.” When it comes to growing food, that means producers focus heavily on making sure the growing environment is as safe as possible.
Farmers continuously evaluate their fields for potential risks.
According to Rock, growers assess their water sources in terms of contamination risk – groundwater tends to be less risky than open-canal irrigation, for example – and chemically treat water from riskier sources. Workers and inspectors monitor fields for signs that wildlife may be present, flagging off any areas of concern so that section of the crop is untouched or even destroyed. Any animal-based fertilizers must be verified for safety, and field managers and harvest crews receive regular training on proper hygiene to prevent human transmission of pathogens.
Researchers like Kerry Cooper, an associate professor in the School of Animal and Comparative Biomedical Sciences, are investigating methods of preventing contamination from less straightforward sources. His lab studies the genomics, pathogenesis and epidemiology of foodborne pathogens.
“My lab has a big project right now to study weather patterns and how pathogens can be transmitted through extreme weather events, where high winds could blow contaminated material onto fields,” he said. “It’s another way to understand potential risks so we can find ways to mitigate them.”
How does food safety testing work?
In the week before harvest, growers or third-party laboratories collect representative samples for pathogen testing.
Rock explained that samples are ground up and placed in broth cultures to enrich any bacteria present, then screened for at least three of the major bacterial pathogens: E. coli O157:H7, Salmonella and Listeria. If a sample returns a “presumptive positive,” the entire field is destroyed and abandoned.
Testing every individual plant is impossible, due to the sheer scale of most produce farming operations and the destructive nature of the tests themselves – testing every leaf would leave no food left to sell.
“During the peak harvest season in major agricultural hubs like Yuma, producers are shipping an average of 1,000 trucks of leafy greens and other fresh produce every day,” Cooper said. “Growers do their best to get a good sample, but it’s not possible to test every single plant.”
Post-harvest, producers and processors employ safety measures to prevent the introduction of new hazards.
“Any produce that’s labeled as ‘triple-washed’ has gone through a multi-stage flume wash containing disinfectants like low-chlorine solutions or peracetic acid,” said Cooper. “Most produce that isn’t pre-washed has likely still been subjected to a disinfecting protocol.”
Ravishankar explained that for crops with rough, textured rinds like cantaloupes, research shows washing operations can trap moisture and potentially spread pathogens and encourage mold growth. As a result, melons grown in Arizona are generally dry-packed in the field immediately after harvest.
Beyond produce, she noted that post-harvest processors use specialized physical and biological blocks to secure animal-derived products before they reach distribution centers.
“It’s essential to chill meat products as soon as possible following harvest, and to maintain a low temperature until they’re ready to be cooked,” said Ravishankar. “Commercially produced eggs go through a decontaminating wash before being chilled, and dairy should be pasteurized to eliminate bacteria.”
Who enforces food safety rules on farms?
The Food and Drug Administration’s Food Safety Modernization Act Produce Safety Rule sets baseline federal standards for water quality, soil amendments and field sanitation. In addition, state agricultural departments and industry bodies may enforce their own growing metrics.
“In Arizona and California, we have the Leafy Greens Marketing Agreement (LGMA), which provides guidance for growing, packing and shipping of leafy greens,” Rock said. “That provides an additional level of oversight, where external testers review a grower’s practices to make sure they’re compliant with those metrics.”
U of A scientists actively support Arizona growers through research and Cooperative Extension services that assess and suggest improvements to food safety practices.
Rock noted that Arizona growers can invite Extension specialists to go over their processes in advance of LGMA audits and identify what’s working and where improvements could be made. Extension has also developed a program with the Arizona Department of Agriculture called On-Demand Harvest Worker Training, in which a food safety specialist delivers on-site safety training directly to harvest workers.
Food retailers, processors and shippers often have their own requirements beyond those required by federal, state and local regulators.
“Food producers take safety very seriously,” Cooper said. “If people truly knew how much effort goes into getting food to the grocery store or restaurant, they’d have a newfound respect for our food safety systems.”
Scientifically reviewed by: Sadhana Ravishankar, Channah Rock, & Kerry Cooper