How does peanut butter even become contaminated with salmonella?

How does peanut butter even become contaminated with salmonella?

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

According to an updated press release issued Thursday by the Centers for Disease Control and Prevention, 16 people in 12 states became infected with salmonella — a bacteria that can cause gastrointestinal illness — after eating some Jif peanut butter products.

The CDC, along with the U.S. Food and Drug Administration and other public health officials in affected states, continues to investigate the multistate outbreak. All affected peanut butter products – nearly 50 different items – were manufactured at the JM Smucker Company plant 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 these products and throw them away or return them to the store if they are affected.

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

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

Manufacturing problems can lead to thisSalmonellain peanut butter

To understand the connection between peanut butter andSalmonella, it's important to think about how peanut butter is made. The process of making peanut butter begins with raw, shelled peanuts that are roasted and cooled, Dr. Vijaya Surampudi, clinical nutrition specialist at UCLA Health, told Health. The peanuts are then ground and reheated during the milling, she added.

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

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

Roasting the contaminated peanuts can help kill the salmonella "if the food is heated to a high enough temperature, held at that temperature long enough, and cooked consistently," Detwiler said. But then the peanut butter must maintain this hygienic state 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. “This is why cleaning and disinfecting the equipment and facility is so important, in addition to ensuring the facility is well maintained,” Ellen Shumaker, PhD, food safety associate at North Carolina State University, told Health.

Is peanut butter healthy? Here's what nutritionists say you should know

Peanut butter is an ideal place forSalmonellaSurvive

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 water available to support the growth of microbial pathogens like salmonella,” Abby Snyder, PhD, assistant professor of food science at Cornell College of Agriculture and Life Sciences, told Health. “But whileSalmonellacannot grow, it can survive for long periods in low-moisture foods such as peanut butter.

According to Shumaker, the high fat content of peanut butter can even act as a protective layer for the bacteria. She pointed to a 2000 study in the Journal of Applied Microbiology that found the bacteria in peanut butter jars can survive for up to 24 weeks.

Another big problem: Peanut butter is considered a "ready-to-eat" food, meaning people typically eat it without cooking it — which then increases the risk of contracting salmonella if the jar is contaminated, Snyder said.

What to do if you have a reminder of peanut butter at home – and what to do about future outbreaks?

The FDA and CDC both recommend not eating the recalled Jif peanut butter products; they should be thrown away or returned to the store. This also applies to pets or other animals - they should not be fed the potentially contaminated products either.

Authorities also suggest that you wash surfaces and containers that have come into contact with the affected food with hot, soapy water.

If you have eaten any of the recalled products and feel sick - which can occur within 12 to 72 hours of a salmonella infection - you should contact your doctor. The most common symptoms of infection with the bacteria (salmonellosis) are: diarrhea, sometimes bloody diarrhea; a fever higher than 102 degrees Fahrenheit, excessive vomiting, and dehydration.

The recent outbreak shows that the entire food industry “must always be on high alert for salmonella,” Shumaker said. Although the FDA has updated recommendations and created more stringent food safety standards in recent years – most notably 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 away from the products,” Detwiler said. “Frequent and effective testing and appropriate measures are needed to prevent such events from harming and killing consumers and to comply with regulatory and legal obligations.”

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