An Iowa Dining Staple is Becoming a Haven for Bacteria

For years, onions have been a trusted kitchen and dining staple in Iowa, a key ingredient in everything from comforting casseroles to hearty stews and always topping your favorite tenderloin, burger, or brat. Their natural antimicrobial properties and protective outer layers have long made them a low-risk food when it comes to bacteria. However, recent outbreaks of foodborne illnesses have left many Iowans rethinking how they handle, and eat, this kitchen essential.

The most notable incident was tied to yellow onions served at McDonald’s, which caused an outbreak of E. coli O157:H7 infections in 14 states, including parts of the Midwest. While the situation has since been resolved, it has raised questions about onion safety and the broader challenges of preventing foodborne illnesses. Especially with a food that is so widely used across all types and styles of food.

The McDonald’s Outbreak

The FDA, CDC, and state agencies traced the outbreak to yellow onions distributed by Taylor Farms and used in McDonald’s menu items. On October 22nd, 2024, Taylor Farms initiated a voluntary recall of the onions and alerted affected food service customers, including McDonald’s.

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Although investigators couldn’t find the exact strain of E. coli linked to illnesses in onion or environmental samples, epidemiological evidence strongly pointed to the recalled onions as the source. Of 81 people interviewed during the investigation, 99% reported eating at McDonald’s, and 84% recalled consuming items containing "fresh" slivered onions.

The outbreak affected 104 people, some severely, but with the recall in place, McDonald’s stopped serving the implicated onions and went to a different distributor. Federal agencies have declared the outbreak over, and the investigation has now been closed.

But onions were always thought to be a safer plant food item, why are they causing problems now?

Despite their reputation for safety, onions can become contaminated at various points in the supply chain. Contaminated irrigation water, exposure to animal waste, and mishandling during processing are common culprits. Precut onions, like the slivered ones used by McDonald’s, pose an even higher risk due to increased surface area for bacteria to spread.

While onions undergo a curing process that helps kill bacteria, it’s not always foolproof. Bacteria can sometimes survive, especially if curing isn’t thorough or if the onions are damaged during harvest. Bacteria contamination of onions include E. Coli, Salmonella, and even Listeria.

Fortunately, there are steps you can take to safely enjoy onions in your meals:

• Choose Whole Onions: Whole, uncut onions with intact skins are your safest option. Precut or prepackaged onions, while convenient, carry higher risks. This is how fast-food dining options can create a massive outbreak in a short amount of time.
• Wash and Peel: Rinse onions under running water and peel away the outer layers before use. Even if you plan to cook them, it’s best to start clean.
• Cook Thoroughly: Cooking onions to at least 165°F kills harmful bacteria. Consider this for recipes that typically use raw onions, like salsas or salads.
• Store Properly: Keep onions in a cool, dry place with good ventilation to prevent bacterial growth.

The McDonald’s outbreak underscores a larger issue: food safety isn’t guaranteed, even for ingredients, and retailers, we often assume are safe. Contamination can happen anywhere along the supply chain, and even advanced food safety technologies can’t always pinpoint the exact source of an outbreak.

What it essentially comes down to is pre-packaged foods are much more dangerous when it comes to bacterial exposure than the fresh ingredient option, especially when it comes to onions. Contamination can essentially happen anywhere, but if a supplier were to be infected, like in this instance, wouldn't it essentially have been better to just prepare the veggies yourself? I understand it's not exactly cost effective in most cases, but in this instance I'm sure the savings in bad PR would have been well worth it.

For Iowans, the best approach is caution and care. By choosing whole onions, handling them properly, and cooking them when possible, you can continue to enjoy this versatile ingredient with confidence. While the recent outbreaks are concerning, they are rare, and with a few extra precautions, onions can remain a staple in Iowa’s beloved dishes, at fast-food stops and restaurants across the Tri-States.