How did my peanut butter get contaminated with Salmonella?

Answers to your questions about the news.
Feb. 20 2007 7:05 PM

Peanut Butter and Salmonella

Who put bacteria in my PB&J?

Download the MP3 audio version of this story here, or sign up for The Explainer's free daily podcast on iTunes.

Peanut Butter. Click image to expand.
Peanut butter

Hundreds of people have contracted salmonella poisoning from contaminated jars of peanut butter, the FDA announced last week. ConAgra, the manufacturer responsible for the outbreak, will shell out more than $50 million to recall all of the Peter Pan and Wal-Mart "Great Value" brand peanut butter made at its plant in Sylvester, Ga. Wait, can you really get salmonella from peanut butter?

Daniel Engber Daniel Engber

Daniel Engber is a columnist for Slate

Yes. Poultry, meat, and eggs provide the most common source of salmonella infection and the associated disease "salmonellosis." The bacteria live in animals like cattle and birds and can easily be passed along in raw animal products. But the feces of infected animals can also contaminate many other foods, like fresh fruits and vegetables. Last week, Dole recalled cantaloupes that contained the bacteria, and in 2004, Roma tomatoes were contaminated.

Peanut butter happens to be a pretty safe food when it comes to microorganisms. That's because the nuts are blanched, roasted, and ground up at temperatures high enough to kill any salmonella bacteria that might have gotten into the raw ingredients. But the germs can still contaminate the product in the "post-processing" phase of production—when the finished product is loaded into jars and labeled for sale. The only other known outbreak of peanut butter-related salmonellosis occurred in Australia in the mid-1990s: Post-processing contamination with fecal matter was the likely culprit.

Both the Australian and the recent American peanut butter outbreaks involved unusual strains of the bacteria—Salmonella Mbandaka and Salmonella Tennessee. The genus Salmonella comprises more than 2,000 different kinds of microbe, some more dangerous than others. The most deadly, Salmonella Typhi, affects the developing world and causes Typhoid fever. In the United States, the most common are Typhimurium and Enteritidis, both of which turn up with some regularity in the poultry supply. Like Tennessee, many strains are named after the locations where they were first discovered. Arizonae, for example, often turns up in fauna typical of the Southwest. (People who eat rattlesnakes or keep iguanas for pets are at particularly high risk.) Other varieties include Salmonella Saintpaul, Salmonella Jerusalem, and Salmonella Newjersey.

Bonus Explainer: Are Peter Pan and Great Value peanut butter the same, since they're made in the same plant? Not necessarily. While the recipes could be exactly the same, they could also be somewhat different. (Great Value, for example, might have fewer crunchies.) A large food manufacturer like ConAgra uses its facilities to produce its own regular, branded products (like Peter Pan peanut butter), but it can also contract out production of "private label" brands under the specifications of giant supermarket chains like Wal-Mart.

Got a question about today's news? Ask the Explainer.

Explainer thanks Michael Doyle of the University of Georgia and Dane Twining of the Private Label Manufacturers Association. 

TODAY IN SLATE

Medical Examiner

The Most Terrifying Thing About Ebola 

The disease threatens humanity by preying on humanity.

I Bought the Huge iPhone. I’m Already Thinking of Returning It.

Scotland Is Just the Beginning. Expect More Political Earthquakes in Europe.

Students Aren’t Going to College Football Games as Much Anymore

And schools are getting worried.

Two Damn Good, Very Different Movies About Soldiers Returning From War

The XX Factor

Lifetime Didn’t Think the Steubenville Rape Case Was Dramatic Enough

So they added a little self-immolation.

Politics

Blacks Don’t Have a Corporal Punishment Problem

Americans do. But when blacks exhibit the same behaviors as others, it becomes part of a greater black pathology. 

Why a Sketch of Chelsea Manning Is Stirring Up Controversy

How Worried Should Poland, the Baltic States, and Georgia Be About a Russian Invasion?

Trending News Channel
Sept. 19 2014 1:11 PM Watch Flashes of Lightning Created in a Lab  
  News & Politics
Weigel
Sept. 20 2014 11:13 AM -30-
  Business
Business Insider
Sept. 20 2014 6:30 AM The Man Making Bill Gates Richer
  Life
Quora
Sept. 20 2014 7:27 AM How Do Plants Grow Aboard the International Space Station?
  Double X
The XX Factor
Sept. 19 2014 4:58 PM Steubenville Gets the Lifetime Treatment (And a Cheerleader Erupts Into Flames)
  Slate Plus
Slate Picks
Sept. 19 2014 12:00 PM What Happened at Slate This Week? The Slatest editor tells us to read well-informed skepticism, media criticism, and more.
  Arts
Brow Beat
Sept. 20 2014 3:21 PM “The More You Know (About Black People)” Uses Very Funny PSAs to Condemn Black Stereotypes
  Technology
Future Tense
Sept. 19 2014 6:31 PM The One Big Problem With the Enormous New iPhone
  Health & Science
Bad Astronomy
Sept. 21 2014 8:00 AM An Astronaut’s Guided Video Tour of Earth
  Sports
Sports Nut
Sept. 18 2014 11:42 AM Grandmaster Clash One of the most amazing feats in chess history just happened, and no one noticed.