How Does Peanut Butter Get Contaminated With Salmonella, Anyway?

Fact checked on May 27, 2022 by Vivianna Shields, a journalist and fact-checker with experience in health and wellness publishing.

Sixteen people across 12 states have been infected with Salmonella—a bacteria that can cause gastrointestinal illness—reportedly after eating some Jif peanut butter products, according to an updated news release shared from the Centers for Disease Control and Prevention.

The CDC, along with the U.S. Food and Drug Administration and other public health officials in the affected states, continue to investigate the multi-state outbreak. All of the affected peanut butter products—nearly 50 different items—were produced at the J.M. Smucker Company facility in Lexington, Kentucky.

The products have been voluntarily recalled and are off store shelves, but people who have Jif peanut butter products at home are urged to check the lot codes on those products, and throw them away or return them to the store if they contain 425 as the last three numbers.

The current Salmonella investigation adds to the growing list of past outbreaks in peanut butter products—the most notable of which occurred in 2008–2009 when 714 people were sickened and nine people died due to contaminated King Nut brand creamy peanut butter. Another 2012 outbreak linked Trader Joe's peanut butter (made by Sunland, Inc.) to 42 Salmonella infections; and in 2015 JEM Raw brand sprouted nut butter was the cause of 13 Salmonella-related illnesses.

This all begs the question: How does peanut butter become contaminated with Salmonella—a bacteria most often associated with raw poultry or eggs—and what seems to make it so susceptible to the contamination? Here's what to know.

Manufacturing Issues May Lead To Salmonella in Peanut Butter

To understand the link between peanut butter and Salmonella, it's important to go over how peanut butter is made. The process of making peanut butter starts with raw, shelled peanuts that are roasted and cooled, Vijaya Surampudi, MD, clinical nutrition specialist at UCLA Health, told Health. The peanuts are then ground, and heated again during the grinding, she added.

Heating the peanuts and keeping them dry is a hugely important step in keeping your peanut butter safe from contamination, Darin Detwiler, LPD, a professor of food policy and corporate social responsibility at Northeastern University and author of Food Safety: Past, Present, and Predictions, told Health.

"Peanut butter is made from shelled and ground peanuts that are typically left sitting in unprotected piles until ready for the next stage of food manufacturing or for delivery to another company," said Detwiler. "Most cases of Salmonella in peanuts are caused by the presence of rainwater bringing feces onto the product, or animals—birds, or more likely rodents—[coming] directly] into contact with the product."

Roasting the contaminated peanuts can help kill Salmonella "if the food is heated to a high enough temperature, held at that temperature for enough time, and cooked throughout," said Detwiler. But then the peanut butter has to keep that sanitized status after heating and grinding. "Roasted peanut butter can become contaminated in the processing plant if proper sanitation protocols are not followed."

However, in some cases roasting contaminated peanuts can actually cause a type of heat-tolerant bacteria. "That's why cleaning and sanitizing of the equipment and the facility is so important in addition to ensuring that the facility is well maintained," Ellen Shumaker, PhD, food safety extension associate at North Carolina State University, told Health.

Peanut Butter Is an Ideal Place for Salmonella To Survive

According to Detwiler, Salmonella may not be able to grow in peanut butter, but it can survive for "many months" if it gets into the product.

"Peanut butter is a low-moisture food, meaning there is not enough available water to support the growth of microbial pathogens like Salmonella," Abby Snyder, PhD, assistant professor of food science at the Cornell College of Agriculture and Life Sciences, told Health. "However, while Salmonella can't grow, it can survive for extended periods of time in low-moisture foods like peanut butter."

The high-fat content of peanut butter may even act as a layer of protection for the bacteria, according to Shumaker. She pointed to a 2000 study in the Journal of Applied Microbiology which found that the bacteria could survive for up to 24 weeks in peanut butter jars.

Another large issue: Peanut butter is considered a "ready to eat" food, meaning people typically eat it without cooking it—which then raises the risk of contracting Salmonella, if the jar is contaminated, said Snyder.

What To Do if You Have Recalled Peanut Butter at Home—and What's Being Done About Future Outbreaks?

The FDA and CDC both recommend that people do not eat the recalled Jif peanut butter products; they should be thrown away or returned to the store. That goes for pets or other animals, too—they should also not be fed the potentially contaminated products.

The agencies also suggest that you wash surfaces and containers that have touched the affected foods using hot, soapy water.

If you have eaten any of the recalled products and start feeling ill—which can happen within 12 to 72 hours following a Salmonella infection—you should contact your health care provider. The most common symptoms of an infection with the bacteria (salmonellosis) include diarrhea, sometimes bloody diarrhea; a fever higher than 102 degrees Fahrenheit, excessive vomiting, and dehydration.

The latest outbreak shows that the entire food industry "always needs to be on high alert for Salmonella," said Shumaker. Though in recent years the FDA has updated recommendations and created more rigorous standards regarding food safety—particularly with the Food Safety Modernization Act of 2011—companies must continue to invest in and prioritize food safety and sanitation plans.

"This must include structural elements that can keep rodents and rainwater out of the products," said Detwiler. "Frequent and effective testing, as well as appropriate actions, are needed to prevent such events from harming and killing consumers as well as to meet regulatory and legal responsibilities."