The Skeptical Teacher

Musings of a science teacher & skeptic in an age of woo.

The Myth of the Non-Decomposing McDonald’s Hamburger

Posted by mattusmaximus on November 14, 2010

So a few weeks ago some people I knew were passing around an article on Facebook about an “experiment” some woman had done which showed that a McDonald’s meal wouldn’t decompose. The interpretation by many was that this was proof of how unhealthy McDonald’s food is because it is apparently “too full of preservatives” and it is somehow “unnatural” because natural foods rot.  Some people have even gone so far as to argue that there are artificial materials within McDonald’s food such as plastic!

Of course, all of these arguments are variations on the naturalistic fallacy, and they can be easily disproven with some simple experimentation.  In fact, a number of home-grown experiments have been performed which show that the reason why McDonald’s food, and any kind of food for that matter, doesn’t decompose in these examples is because it is allowed to dry out.  And if you know anything about preserving food (hint: think beef jerky), one way to do it is to simply dehydrate it.  If the food dries out, then there is no moisture to support the growth of mold, bacteria, and other microorganisms which would otherwise decompose it.  Essentially, the food is mummified.

For more details on this subject, I suggest looking at following article which takes a very detailed & scientific look at the question:

The Burger Lab: Revisiting the Myth of The 12-Year Old McDonald’s Burger That Just Won’t Rot (Testing Results!)


[Photographs: J. Kenji Lopez-Alt]

A few weeks back, I started an experiment designed to prove or disprove whether or not the magic, non-decomposing McDonald’s hamburgers that have been making their way around the internet are indeed worthy of disgust or even interest.

By way of introduction, allow myself to quote myself. This is from myprevious article:

Back in 2008, Karen Hanrahan, of the blog Best of Mother Earth posted a picture of a hamburger that she uses as a prop for a class she teaches on how to help parents keep their children away from junk food… The hamburger she’s been using as a prop is the same plain McDonald’s hamburger she’s been using for what’s now going on 14 years. It looks pretty much identical to how it did the day she bought it, and she’s not had to use any means of preservation. The burger travels with her, and sits at room temperature.Now Karen is neither the first nor last to document this very same phenomenon. Artist Sally Davies photographs her 137 day-old hamburger every day for her Happy Meal Art Project. Nonna Joann has chosen to store her happy meal for a year on her blog rather than feed it to her kids. Dozens of other examples exist, and most of them come to the same conclusion: McDonald’s hamburgers don’t rot.

The problem with coming to that conclusion, of course, is that if you are a believer in science (and I certainly hope you are!), in order to make a conclusion, you must first start with a few observable premises as a starting point with which you form a theorem, followed by a reasonably rigorous experiment with controls built in place to verify the validity of that theorem.

Thus far, I haven’t located a single source that treats this McDonald’s hamburger phenomenon in this fashion. Instead, most rely on speculation, specious reasoning, and downright obtuseness to arrive at the conclusion that a McDonald’s burger “is a chemical food[, with] absolutely no nutrition.”

As I said before, that kind of conclusion is both sensationalistic and specious, and has no place in any of the respectable academic circles which A Hamburger Today would like to consider itself an upstanding member of. …

Just to jump to the end of the article, here are the results of the extensive testing performed:

The Results


Well, well, well. Turns out that not only did the regular McDonald’s burgers not rot, but the home-ground burgers did not rot either. Samples one through five had shrunk a bit (especially the beef patties), but they showed no signs of decomposition. What does this mean?

It means that there’s nothing that strange about a McDonald’s burger not rotting. Any burger of the same shape will act the same way. The real question is, why?

Well, here’s another piece of evidence: Burger number 6, made with no salt, did not rot either, indicating that the salt level has nothing to do with it.

And then we get to the burgers that did show some signs of decay.

Take a look at both the homemade and the McDonald’s Quarter Pounder patties:


Very interesting indeed. Sure, there’s a slight difference in the actual amount of mold grown, and the homemade patty on the right seems to have shrunk more than the actual Quarter Pounder on the left (I blame that mostly on the way the patties were formed), but on the whole, the results are remarkably similar. That a Quarter Pounder grows mold but a regular-sized McDonald’s burger doesn’t is some pretty strong evidence in support of Theory 3 from above. Because of the larger size of a Quarter Pounder, it simply takes longer to dehydrate, giving mold more of a chance to grow.

So folks, the bottom line is that McDonald’s food behaves just like any other kind of food. If you let it dry out, it won’t rot; if you keep it moist so that bacteria & mold can grow on it, it will rot.  If you don’t believe me, just feel free to conduct your own test – more on how to do that in the article I posted above.

And for those of you who want to make a big deal out of this thing, that McDonald’s food is supposedly bad for you because “it won’t rot”, then I think you really need to find something else to get concerned about because this one is just a fool’s errand.

60 Responses to “The Myth of the Non-Decomposing McDonald’s Hamburger”

  1. […] This post was mentioned on Twitter by fastfoodjunky, Matt Lowry. Matt Lowry said: The Myth of the Non-Decomposing McDonald’s Hamburger – […]

  2. Anne said

    Have you seen “Supersize Me”? If I recall, I think the dude in there did something with rotting\not rotting. Maybe I’m misremembering, but I think so ….

    • Julia said

      You remember correctly Anne, but in the Supersize Me extra, the food items were placed in sealed glass canisters. This would negate the ‘drying out’ argument, because any moisture contained in the food is captured inside the canister. The food items may not start out with the same amount of moisture, if one really wanted to conduct a true experiment, this would have to be accounted for in some manner. Also, I want to point out that neither this blog article, nor the extra on Supersize Me, are discussing true experiments. While they are interesting, and make us wonder about the implications of what we are witnessing, without a true experiment we are only guessing at what is happening and what it means.

    • Reminds me of the recent Rizzoli & Isles episode where Dr Isles mentions the content of the cupcake (or such) that Rizzoli is trying to eat and Rizzoli says, “but it tastes so good.”

  3. April McCauley said

    Where do the components of his homemade patty come from? I would have been curious to see an organic one in there to control for processing. “Eat This, Not That” said in one of their articles that fast food beef is rinsed with ammonia to keep it from spoiling. The ammonia is a “processing” chemical so is not listed in ingredients anywhere, according to them. I have no idea if the same processing happens to supermarket beef. Based on what he has shown above, though, the extent to which something has been exposed to ammonia in processing could account for the amount of mold growth (hypothetically, the fast food beef should have more exposure than the supermarket beef?). This guy’s experiment might just show that all the beef is relatively chemical-ized rather than that the McDonald’s isn’t. So, anyway, there’s my speculation- just curious if you have anything about the use of ammonia, reliability of Eat This Not That, etc.

    • mattusmaximus said

      If ammonia makes beef anti-moldy, then why did the burgers (both McDonald’s and home-made) which retained moisture grow mold & ultimately decompose? In both cases, by your argument, there was ammonia and so the burgers should not have gotten moldy – but this apparently didn’t matter when moisture was present, as the burgers grew mold. But when moisture was removed the burgers didn’t decompose. Thus, based upon these experiments, the important variable is moisture.

      • April McCauley said

        I don’t think that ammonia makes it 100% sterile or can prevent it from being contaminated, later. Their term was “rinsed” not “mixed.” And, anecdotally at least, moisture makes lots of mold grow better, that’s one of the reasons there are exhaust fans in bathrooms- to vent the moisture when you run the shower. The level of moisture probably makes a big difference in the decomposition rate of lots of things. I agree with your overall statement that it is a meat product that will eventually decompose and that it will decompose faster with moisture present, I just think that it (and all of the beef processed in the industrialized system) is treated to slow that decomposition rate at a given level of moisture. Anyways, I’m not obsessed, just curious if you had more info. No worries.

    • Kthx said

      I have no love lost for McDonalds, but there needs to be some honesty form those who are purporting to ‘educate’ people about the evils of Capitalistic Corporations by selling them books, pills etc. and “The Secret” is contained within half truths, fallacies, or outright lies

      The argument of Ammonia is moot regardless of how you spin it, as only MSP (Mechanically Separated Poultry) and MSM (Mechanically Separated Meat) products are rinsed with ammonia during their production. These products would include things like Hot Dogs, Chicken McNuggets, and Meat Patties for frozen meals.

      You can check the sources in this Snopes article, but be warned for the pictures of processed meat, and the discussion of meat production techniques.

    • Andrew said

      Did you know that there are different kinds of ammonia chemicals? Maybe they use the same kind of ammonia one would use for cleaning floors; maybe not.

    • In any case, even if the supermarket-bought burgers were treated the same way as the McDonalds burgers… can’t we agree that both are safe to eat?
      The proof is in the millions of people who eat burgers all the time and haven’t died. Many even lead healthy, active lifestyles. If this food was killing us, I think we would notice.

  4. robyn hancock said

    all processed beef is made under the same circumstances,so the natural product should be used to even out the field.

  5. If you go to the original site with the picture you can clearly see the wrapping used for the Hamburger. On the wrapping it claims 100% Beef, but there is another interesting tidbit, the three words “I’m lovin’ it”. That catch phrase started as a global campaign simultaneously in more than 100 countries, get this, in 2003. Here’s a wikipedia article about the History of McDonald’s. This alone should lead you to know that her claims are fraudulent. At best the burger is 5 years old, but as we see from these experiments that being more than a week old is pushing it.

    • Jamie J. said

      Wikipedia, really? Anyone can update that site with whatever they want. So using it as a reference is totally bogus.

      • Neil B. said

        But little to no one does.

      • Mats said

        And you can view the history of any page, to see every change that has been made ever since it was created – which is much better than nearly all other web-sites, that DON’T provide any history [unless you can find some copy of it that shows the content in an older form].


      • Chris said

        Actually, it’s been shown that Wikipedia is about as accurate as the Encyclopedia Britannica. So that would make it pretty accurate. They do have citations and everything, just like a regular encyclopedia. The only difference is that it’s free, and most any body can add to the body of knowledge. However, it has the ability to be peer reviewed. The stigma of Wikipedia may never go away with some people, but then again, there are people who still believe Earth is flat. Go wiki Flat Earth Society sometime.

  6. […] […]

  7. Andrew said

    I’m under the impression that the lack of mold growth has more to do with the dessication of the product over anything else. If it was kept in a sealed container where the moisture was kept in it, I think it, and anything would get much more moldier. Just a thought though…

  8. Heather said

    Who cares how long it takes to mold…fast food is just plain disgusting and filled with all kinds of processing agents, as is a lot of food we eat today. People that preach about how horrible mcdonalds is, then heat up a microwavable packaged lunch, are kind of missing the point also, I switched to a whole foods plant based diet a while ago and even I know I’m still getting chemicals from pesticides probably because I don’t grow my own food. However I eat the best that I can for my circumstances. Honestly I don’t really see too much wrong with telling people a year old hamburger hasn’t molded if it gets people to stop eating them, but I think there needs to be much more food/nutrition education past that.

    • Stacy said

      So it’s ok to lie to people about how things work if it gets them to do something? Um…

      • John Baker said

        Unfortunately, a lot of people seem to feel that lying “for a good cause” is perfectly OK. It isn’t. No matter how fervently you believe in something, if you have to lie to people to get them over to your side, you’re proving only that the truth isn’t all that convincing.

    • Andrew said

      I had a high-fat, high-sodium ultimate cheeseburger from Jack-In-Box. Not only did I enjoy sinking my teeth into it, and liked the taste, but whadda know – I’m still alive.

    • John Baker said

      It’s never OK to lie, Heather, no matter how good your intentions. When you lie, you hurt your cause. As a fellow named Einstein once said, a man who is careless with the truth in small matters cannot be trusted in matters of importance.

  9. […] course, I am not the only person to answer these claims.  I found this wonderful blog entry about a study debunking the whole thing.  In short, if you leave a burger and a bun, any burger […]

  10. Quora said

    Why does a McDonald’s meal never seem to rot?…

    Here’s a link where the author actually compare a McDonalds hamburger to one made at home and compares the decay. Spoiler: identical results. “A number of home-grown experiments have been performed which show that the reason why McDonald’s food, and …

  11. […] The myth of the non-decomposing hamburger Of course, all of these arguments are variations on the naturalistic fallacy, and they can be easily disproven with some simple experimentation.  In fact, a number of home-grown experiments have been performed which show that the reason why McDonald’s food, and any kind of food for that matter, doesn’t decompose in these examples is because it is allowed to dry out.  And if you know anything about preserving food (hint: think beef jerky), one way to do it is to simply dehydrate it.  If the food dries out, then there is no moisture to support the growth of mold, bacteria, and other microorganisms which would otherwise decompose it.  Essentially, the food is mummified. […]

  12. Cátia Borges said

    Did you use home made bread and hamburger made at home with meat? I don’t call that kind of bread or patties bought in the supermarket home made they are already full of preservatives. Most of burger bread have an expiration date superior to 2 weeks, that is far from natural. If I put a beef or home made bread in a plate and leave in my kitchen the beef in 2 days will have an awful smell and starts to get green and moldy. Bread can take a bit more, but in 1 week is already spoiled. Use those and then see the difference between really home made things and pre made ones.

  13. […] countless articles will appear explaining why this is just silly…my favorite article was from The Skeptical Teacher with the following quote (emphasis mine): Of course, all of these arguments are variations on the […]

  14. Esther said

    I’m just glad the only burgers I eat are lentil or chick pea burgers!

  15. EricBlair said

    I may have missed it amidst all the commentary, but did anyone test the actual NUTRITIONAL value of the meat over time? Does the protein or fat content change? Are there changes in vitamin and mineral efficacy – are they there to begin with? I’ve eaten, without any obvious harm to myself, canned food or dried grains that have been in storage for years, but I’m never confident there’s much left besides caloric content.

    • Proteins and fats can be quite resilient, they dont degrade over time unless they are heated, but vitamins have higher chances of being leached out in cans. But when freeze dried such as this burger they can remain frozen in state until ready, though you will loose some when it thaws, the duration of freezing plays no role.

  16. I find your absolute faith in skepticism disturbing.

  17. […] calling foul on this story.…lds-hamburger/…urgers-go-bad/ […]

  18. […] […]

  19. Moreover, you can see that mold is at the center of the burger, exactly where you would expect the most moisture to remain. A useful concept here is “water activity” (you may want to link here
    We even have whole loaves of bread from Ancient Egypt! I don’t think that those Egyptians can be accused of using wicked contemporary preservatives. The operative word here is desiccation. You would not want to eat that bread of course.
    In Southern Italy there is a traditionaltype of extremely dry biscuit/bread called “frisa”. It keeps for months and even years *if stored under dry conditions*. And there is nothing McDonaldish about it.

  20. […] […]

  21. […] The Skeptical Teacher tiene la respuesta: […]

  22. Sue Jensz said

    Why anyone would eat the food fresh or otherwise is beyond my comprehension.

  23. To anyone who is still doubting that this is a myth even after reading the article, please take a food safety course sometime. Food borne bacteria needs six things in order to survive and cause rot and molding. These six things are 1) a Food source 2) proper Acidity levels 3) Time to reproduce and grow 4) appropriate Temperature 5) Oxygen (or for anaerobic bacteria, the absence of oxygen) and, finally, 6) MOISTURE. These six things are easily remembered by using the nemonic anagram FAT TOM. If bacteria doesn’t have these six things, it will NOT grow and cannot cause spoilage. A dried-out burger, no matter where it comes, from will not rot. Period.

    • It is amazing the conclusions you derive when you only know half the truth. This article and in particular Mr Jensen response clearly gives truth and destroys this myth-of-the-non-decomposing-mcdonalds-hamburger, plus I learned about FAT TOM. Thanks

  24. Fetherwood said

    Well…all i knowis margarine last forever out in the open…no bugs will touch it!!!!!!

  25. Wow.. you need to be sincerely ashamed of yourself.

  26. Thanks for this article. I thought about doing the same experiment, because the whole ‘Mc food doesn’t rot’ talking point sounded like bullshit to me and I was curious if it holds up, which it obviously doesn’t.

  27. sabrina said

    You lost me when you said the homemade burger was the same as the McDonald’s. You said it was duebto the way they formed it. The fact It was smaller and had more mold proves that decomposition was taking place. They were not the same. The fact it was bigger, makes the comparison NoT the same. The homemade burger was smaller becasue it was decomposing faster, not of the way it was formed. That made zero sense. You quickly skipped over that mis conception.

  28. Interesting! 😀

  29. Debbie Miller-Rockenhauser said

    Can you do an experiment on the non-melting ice cream? Seems that ice cream bought in the stores can be put in the sink & left over night & it looks almost the same the following day. Lots of chemicals in that & it makes me so sad to know that even ice cream is not safe.

  30. Keanu said

    McDonalds hamburgers are very good but, you do not know what is in them or if the meat is real.

  31. […] out so many times by so many different people it's been debunked a fair number of times as well.…lds-hamburger/ __________________ Last edited by Aureus; 8th January 2015 at 08:19 […]

  32. The reson that fast food isn’t that good for you because it lots of salt and sugar in it and there are way too many sedentary people today. I don’t care how much you exercise but the fact is if you don’t change your diet you can work out to your blue in the face and not lose any weight. good dite and exercise at the same time will help lose Weight. There are people who are in good shape but are over Weight some people have food allergies or inherited health risks like diabetes heart disease. On the other hand if you are in good shape and at the right weight it’s okay to eat at fast foods once in awhile but don’t make a habit out it. If you stop altogether eating at fast foods like for a year and your really hungry and have to eat your body doesn’t have the enzymes too break down all the saturated fat that fast food’s have in them so you will get sick it is not good to stop eating completely any thing. Fat and sugar are survival foods.

  33. Ihatethem said

    Personally, I think moist burgers are better

  34. the point is, this stuff, in the matter of the meat supply, is raised in inhumane factory farms, loaded with chemicals, and is completely bad for your health….even the fries don’t decompose because of all the preservatives and salt and other chemicals. I’m sorry, but I just want to see people eating food that is real, unadulterated, and nutritious. The obesity thing is a problem with all people born and living after the 1970s, and it isn’t getting any better. So look to what is going in our bodies, and you can understand why. I still refuse to feed my kids this stuff, and until we demand changes, they aren’t going to happen.

  35. said

    This makes me super rethink McDonalds… ahhh! please, can’t they just do quality food??? mold! grose.

  36. […] her counter for years and years was fabulous for turning my kids off fast food. (It has since been refuted but my kids don’t know […]

  37. S Cole said

    Stop blaming everyone else for your bad food habits. As consumers we demanded instant availability and longer shelf lives in grocery stores and restaurants – we got it. As the consumer request starts to shift back to local grown and organic i.e. part of the Farm to Table movement, so be it. You can eat fast food as long as you eat wiser and move more. In response to Super Size Me, there have been other stories covered where people actually lost weight and maintained a healthy status based on their choices eating at Fast Food including McDonald’s. So it is possible to enjoy your fast food and not keel over. Vendors whether the mom and pop restaurant or the fast food chain listen to their customers and provide what they want. Get off everyone else’s table. If you don’t want to eat, don’t. If you don’t like how things are being done, take your business elsewhere. Pay the local farmer to have an animal slaughtered for you, go fishing, go hunting, raise your own farm animals and grow your own garden. Too tired, too lazy to do so then you are contributing to the industrial food production chain through your participation and demands for your menu choices. Get educated and stop the scare tactics.

  38. Jake said

    I don’t have a horse in this race, either way, but how can you call this a scientific experiment and only show the result that supports your conclusion? I even clicked on your link. Where are the pictures of the regular burger and the hand ground burger side by side? Come on, if you want people without an agenda either way to truly believe your results (which as an aside does sound logical) then show all the results. Why just type, none of them showed mold and then not show us??? How much sense does that make?

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