How does salmonella get into peanut butter? And can you kill it once it's there?

The bacterium that sickened more than 400 across the U.S. and killed three is resistant to many sterilization techniques















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Why have these outbreaks only happened in the past 15 years?

Some of these processing plants are quite dated, and that may be part of the problem.  They just haven't been maintained.  Thirty years ago when they were built, they didn't have leaks like that.

Is there any way to destroy the bacteria once it's in there?

Not by current procedures.

Theoretically, you could irradiate it. It's not an approved process. And because it’s a high-fat product, you'd get a lot of off odors because of lipid oxidation.  I'm not sure radiation would be good approach. 

We have done thermal inactivation studies on trying to kill salmonella in peanut butter. But even when you get up to 190 degrees Fahrenheit (90 degrees Celsius), it takes many minutes and might affect the integrity of the product.  Heating may not be an easy fix.

So, how can you keep salmonella out of peanut butter in the future?

The key is to have a rigid system in place that does not allow contamination by water or other vectors after the roasting process.  Water in a peanut butter processing plant is like putting gasoline on a fire.  It will not only spread the salmonella, but the salmonella will grow when water is present.  Salmonella is not likely to grow in a dry environment.



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  1. 1. mcross 09:28 PM 1/13/09

    So, this pretty much means we should not be eating any more peanut butter as a rigid system is not likely to be put into place in these older processing plants. Isn't that right?

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  2. 2. aniux7 10:09 PM 1/13/09

    well, no, the statistics are pretty good, two outbreaks in 15 years. You have a higher risk of getting salmonella form your kitchen counter. :-)

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  3. 3. barfalo 12:20 AM 1/14/09

    I just wonder if any of this salmonella poisoning is from the peanut butter getting contaminated by jelly or jam, or something that needs to be refrigerated, on the knife when a sandwich is made, thereby contaminating the jar of peanut butter.

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  4. 4. will 09:12 AM 1/14/09

    I think these heavy problem should due to the regulation system. If institution has treated the problem seriously in the past years, the disease would not outbreak.

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  5. 5. sforstenzer 04:18 PM 1/14/09

    would gamma irradiation solve many of these outbreaks?

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  6. 6. the gene code 01:09 AM 1/15/09

    well as a gene, scientist i could only imply that food products with all its different kinds and type should have high safty and preventive measurments and standards, to ensure the customer well being. as for contamintation there are many methods which can fix this problem.

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  7. 7. dcheely 01:26 AM 1/16/09

    Look ! It's 2009, if we can put men on Mars we should be able to make our food safe.

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  8. 8. Golbez 05:35 AM 1/16/09

    http://www.metacafe.com/watch/yt-sBNr6BI2zm8/brian_regan_space_epitome_of_hyperbole_best_quality/

    1:21 of this clip is relevant in regards to putting a man on Mar- er, the moon... (mars? What?)

    Oh! Unless that was a hypothetical. Perhaps, yes. Maybe when mankind reaches the moon, all food for human consumption will be saf- ... nope. Still doesn't add up.

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  9. 9. Golbez in reply to Golbez 05:35 AM 1/16/09

    Ack, reaches Mars** :(

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  10. 10. dcheely 09:57 PM 1/16/09

    What ! You can't figure that out ! I didn't say we have put men on Mars, I said if we can. And we can. What I am saying is in this modern age we live in our food should be safer than it was in the olden days, you know way back in the twentieth century. Our food won't be safe until the people who make it understand that when you cut corners to make a little more profit sooner or later it will cost you. And me. Bigger fines and prison might help.

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  11. 11. gussie 05:23 PM 1/17/09

    Mechanic: Somebody set up us genetic bomb.
    Operator: We get salmonella.
    Captain: What !
    Operator: Main screen turn on.
    Captain: It's you !
    NOSTRADAMUS: Hello gentlemen!
    NOSTRADAMUS: All your nuts are belong to us.

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  12. 12. JoshRom 09:36 AM 1/19/09

    MY BODY CONSUMES SALMONELLA FOR ENERGY--LIKE PEANUT BUTTER!!!! AHAHHAHAHA.

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  13. 13. fladave 12:51 PM 1/19/09

    If salmonella was present in a jar of peanut butter you had. Would the hole jar be contaminated, or could it be in one little spot in the jar?

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  14. 14. fladave 12:54 PM 1/19/09

    If salmonella was in a jar of peanut butter, would it be present through out the jar? Or could it be contained in a small part of the jar?

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  15. 15. 1915bond 04:44 AM 1/20/09

    @the gene code

    Am I to trust a "gene, scientist" [sic] that can't spell?

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  16. 16. kw 09:47 PM 1/20/09

    Stomach acid protects us from bacteria in our food. I suspect many people who get sick have little or no stomach acid, either from taking a medicine that lowers or eliminates stomach acid (think "heartburn", "acid reflux", or "acid indigestion " meds), or from aging or surgery. These people should be warned they are more vulnerable and may want to eat cooked, hot food that would have less bacteria.. Making us all eat sterilized food seems excessive.

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  17. 17. kw 09:50 PM 1/20/09

    Stomach acid protects us from bacteria in our food. I suspect many people who get sick have little or no stomach acid, either from taking a medicine that lowers or eliminates stomach acid (think "heartburn", "acid reflux", or "acid indigestion " meds), or from aging or surgery. These people should be warned they are more vulnerable and may want to eat cooked, hot food that would have less bacteria.. Making us all eat sterilized food seems excessive.

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  18. 18. Sarge 08:17 AM 1/23/09

    The existence of salmonella on peanuts can be compared to its potential existence in any of the other foods we commonly think of as being logical carriers. The spinach outbreak is a different issue but peanuts and chicken and beef, are very similar in their susceptibility to be host salmonella as well as a list of other nasties. The resolution of the issue in peanuts should be handled by the same technologies that these other processors use. Federal regulations for the beef, poultry and pork industries require certain intervention systems along the production line to prevent the outbreak of salmonella and these same interventions can be implemented in peanut processing. The technology exists and is readily available, simple to implement and very reliable. Contaminated water and air is the primary culprit in the processing facility and methods of prevention are in widespread use in the industries listed above, with exception to peanut processing. Remember this; salmonella is not selective to the product. It is allowed to exist in the food chain due to inappropriate processing practices. All of this could have been avoided by proper use of existing technology!

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  19. 19. horse 06:29 AM 1/24/09

    As a techno-hippie that has gone back to the land in as many ways as possible, I will tell you the simple truth. You can,t trust a corperation which pays its employees minimum wage and cuts every possible corner to produce a good product. If you want safe food buy it from small farmers and process it yourself.

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  20. 20. horse 06:36 AM 1/24/09

    As a techno-hippie who has actually worked in a food processing plant I will tell yu the simple truth. The employees are paid minimum wage or slightly higher, teated badly and have extremely poor morale. Every possible corner is cut to keep profits up. If there are spills on the floor they are scooped up and put back into the vat. Birds are not to blame, I have been raising exotic birds for many years and know this to be propaganda.
    If you want good food buy it from small local farmers and process it yourself.

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  21. 21. dejavu251 12:36 PM 1/26/09

    Ok, we're talking about radiating our food to make it safe? How about just fixing the leaky roof?!?! Sheesh.

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  22. 22. Cuddlencaress 06:50 PM 1/26/09

    Dang.... who's checking on them silos that hold all them roasted-peanuts ?? Doesn't our Food & Drug Admin ensure that farmers and marketing companies upgrade their storage facilities ????

    Where is this USA heading towards ??? Starvation ???

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  23. 23. Cuddlencaress 06:52 PM 1/26/09

    Dang.... where's this country heading towards ??/!!!

    Does not our Food & Drug Admin check up on the manufacturers and farmers who process peanuts to ensure that their "storage silos" are well-maintained or upgraded to keep our foods safe from them "sea-gulls" ??? What next ?? contaminated milk ????

    LOL .....

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  24. 24. Jim Vaughn 02:05 PM 1/27/09

    This article is all but worthless. It contains 99% BS, 1% speculation as to how fecal matter contacts roasted peanuts, and 0% real information. Why waste time digging for cumbersome facts when you can just regurgitate the middle-school-health-class definition of 'salmonella'. Then, surround the definition with "professionally-concerned" sounding sentences, like "9 out of 10 doctors recommend avoiding foods with 'salmonella' on the label." Instead of journalism, we get condescending BS that treats us like we're children.

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  25. 25. sanitarian 04:35 PM 1/27/09

    Salmonella is inherently associated with mammals, reptiles and birds. The peanuts were contaminated most likely by fecal matter in the field, through a contaminated fomite which came in contact with them, or a food worker who is infected with salmonella and didn't properly wash hands after using the restroom. The means to kill the salmonella is by heating it. That is why the peanuts are roasted. After that kills the bacteria, the equipment must be cleaned and sanitized properly. This should be done on a schedule or any time contamination may have occured. Jars and lids must be sterile for packing. Employees are to take the proper measures to keep from contaminating the peanuts at all times after they have been roasted. Any break down in the system, from a dilapidated faciity, to ill employees can re-introduce bacteria, viruses, etc.

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  26. 26. ildecoll 07:29 PM 1/27/09

    411 on Peanut Butter. Once proccesed, the peanut butter will last a month without refrigeration. After that you need to keep it on the fridge where it will last for a year or less (read exp. date). The time that it gets from Minnesota to the market to your home is already a risk if not taken proper care.

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  27. 27. ildecoll 07:31 PM 1/27/09

    411 on Peanut Butter. Once proccesed, the peanut butter will last a month without refrigeration. After that you need to keep it on the fridge where it will last for a year or less (read exp. date). The time that it gets from Minnesota to the market to your home is already a risk if not taken proper care.

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  28. 28. sanitarian 11:15 AM 1/28/09

    Let's not forget that the consumer is also capable of contaminating the peanut butter once the jar has been opened. Be safe, wash hands and wash and sanitize surfaces and utensils after contact with raw meat, using the toilet, playing with pets, changing a diaper....the list goes on. Never go from handling raw meat to ready to eat items such as salads, sandwiches, cheese, etc. without washing hands thoroughly and using clean utensils.

    Always refrigerate leftovers promptly, uncovered to aid rapid cooling. Cover foods after cooled.

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  29. 29. elyown2 01:09 PM 1/28/09

    I wonder if salmonella has nothing to do with aseptic technique. Although It is a law and an A must to wash hands , people is still ignoring this technique whether they are from the bathroom or finihing taking care of a sick or contaminated patient in which I am a witness. Now some people has bacteria from under the nails or a virus where they are very careless about. I've seen people caugh over food while cooking or sneeze around people and not covering their faces. a food preparing area can also be contaminated becaus of bad air, or little hiding insects probably fell in peanut while preparing it where eyes don't see. So, instead of having inspectors check food preparing areas every month, I think twice a month would be more an appropriate system to use. But, don't also forget that the area where the peanuts were planted, " the soil" may also be contaminated
    I have seen people sweat fall on cooking food while preparing it . The cashier in a fast food restorant is also serving foods with the same hands that touched the money. Now, this is scary; and we must take all the necessary precautions to avoid these types of disasters. for the benefit of humanity in God name,since He gives us knowledges.

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  30. 30. bollweevilsx 09:51 PM 1/28/09

    I am amazed there is not an "outbreak" of one kind or another more often considering the fact the food industry has to keep up with feeding millions and millions of people here in the United States and other countries. We the consumer must be on the alert and keep up with any news breaks involving our food sources. As far as the people who are sick, I wish them wellness soon and God Bless them all. And my prayers are with the families of the victims who succumbed to the bacteria.

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  31. 31. sanitarian 04:14 PM 2/3/09

    Hurrah, Hurrah, elyown2 gets the picture!!! Now if we could just get all food workers to be so conscientious.

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  32. 32. csmjimmorrison 01:15 PM 2/8/09

    Question: Was it the peanut butter or the peanut that the salmonella started in?

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  33. 33. csmjimmorrison 01:17 PM 2/8/09

    Question: Was the salmonella started in the peanut or the processing of peanuts to peanut butter?

    Thanks,

    Jim Morreison

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  34. 34. sanitarian 01:24 PM 2/13/09

    Could have been in either. Depends at what point the peanuts or peanut butter became contaminated. Could have been from the fields, could have been unclean equipment during processing, unsanitized packaging, ill employees, contaminated water... they may track it down, who knows. I have investigated several foodborne illness outbreaks in which we identified the pathogen, but never pinned down the exact cause. In this case, they know the pathogen, they know the source, but as yet haven't pinned down the exact cause. Bacteria are ubiquitous in nature, somewhere in the peanut processing system something broke down. The peanut people caught it through the test results, but chose to ignore solving the problem and sent the product out anyway. Very ignorant, very unresponsible. I don't get it. Well, I guess I do get it....it's called greed.

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  35. 35. jimmy37 02:21 PM 2/14/09

    Since we gave power to the government to protect us, we had better be diligent and make sure the people we put in power do what we want or replace them. Instead of spending money on useless, feel-good projects, we need to properly fund our regulatory agencies and we need to make sure the rules make sense.

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