By now, you’ve seen the pictures online of years- or decades-old McDonald’s meals that look as if they were ordered minutes ago. This strange phenomenon has started an understandable rumor that McDonald’s fast food doesn’t rot. But it’s not that simple of a story: science can explain why these patties and fries never seem to age.
Nutrition and wellness expert Karen Hanrahan brought a very strange issue to national attention. She purchased a McDonald’s hamburger in 1996 and held on to the beef-centered sandwich for a dozen years. After all that time, she said, the meal hadn’t changed or decomposed as you might expect.
Others have repeated Hanrahan’s experiment with matching results. They left their Happy Meals, sandwiches, and fries to sit in glass cases or plastic bags. After months or years of observation, there was little visual change to the food. Naturally, these findings have freaked out the internet for obvious reasons.
Namely, people have long worried that their McDonald’s meals hid secret chemicals meant to keep the burgers and fries fresh for as long as possible. It would make sense to think this when looking at a perfectly intact ten-year-old bun and patty. But in fact the chain hasn’t been pumping its food full of unnatural ingredients to extend its shelf life.
Meanwhile, some wondered if McDonald’s simply wouldn’t rot like other foods do. After all, everyone has opened their fridge at some point to find something moldy or partially decomposed forgotten in a dark corner or back drawer. That’s why it’s so strange to think of a burger sitting on a shelf for years, maintaining its perfectly round shape.
But McDonald’s isn’t rot-resistant, nor is it chemically engineered to last forever. It turns out that these amateur experiments were just that: amateur. And experts have stepped forward to explain why the fast-food burgers and fries fail to break down when left on display for decades.
A 2014 Consumer Reports survey tabulated the opinions of more than 32,000 readers to rank the burger chains that dot the United States. Of all the 21 options on the list, McDonald’s came in dead last. And that decision had to do with more than just the taste of the food.
At that time, McDonald’s fans noted that the fast food chain’s menu wasn’t as cheap as it used to be. Even the famous Dollar Menu had an “& More” added to the end, as not everything could be bought for a buck anymore. Plus, it had added so-called premium items to their offerings, hiking up prices even more.
It wasn’t the first time McDonald’s had made major changes to its menu – ones that surprised the restaurant’s regulars. In 2004, for example, the burger chain announced that it would remove the option to buy super-sized fries and drinks to go with its already indulgent mains.
At the time, McDonald’s representatives said it had gotten rid of the massive portion option in an attempt to streamline its menu. But others thought that the move had been a response to the country’s desire for healthier meals, even when dining at fast-food chains. And McDonald’s did heed that demand too, adding three salads to its menu the year before removing super-sizing from it.
The year 2004 brought the end to McDonald’s super-sizing, and that may or may not have had to do with a documentary about the fast-food chain. It was aptly titled Super Size Me, and, in it, filmmaker Morgan Spurlock fulfilled a promise to eat only McDonald’s for every meal for a month.
Spurlock also vowed to eat everything on the menu at least once. He would only eat and drink from McDonald’s too. That meant he wouldn’t even drink water if it didn’t come from the Golden Arches. On top of that, the documentarian cut down on exercise to match the daily routine of the average American.
You can probably imagine how things turned out for the documentarian at the center of Super Size Me. He packed on 18 pounds in a month, and his cholesterol levels spiked. Spurlock also reported feelings of depression, and his girlfriend said he had lost his zest in the bedroom, to boot.
Once the documentary had come out, it had a serious effect on those who watched it. People began to wonder where its food came from and how it was made. Dietician Christy Harrison explained to women’s media website Refinery 29 in 2017, “Americans started thinking a lot more critically about where its food comes from and the overall food system in this country.”
Harrison went on to say, “In itself, this was not a bad thing – and actually it helped push some food producers to start using more sustainable practices in growing our food and offer more reasonable portion sizes at restaurants.” McDonald’s has long denied that the flick had anything to do with its decision to cut super-sized portions from the menu, though.
Perhaps most of all, Super Size Me made people more aware of the fact that its food can have a huge effect on its bodies. Spurlock gained almost 20 pounds in a month when he ate only McDonald’s, after all. The public wanted more labeling and became more aware of how highly processed their meals were before they ended up on their plates.
On that note, McDonald’s has repeatedly come under fire for how it produces its burgers, fries, and more. And that started years before Spurlock brought the unhealthiness of fast food to a national stage. In 1996 Karen Hanrahan bought a McDonald’s burger, but the wellness educator had no intention of eating it.
Instead, Hanrahan held on to the burger for the next dozen years to see how the grilled sandwich would break down. In 2008 – a whopping 12 years after she bought the McDonald’s meal – she revealed that the composition of the burger hadn’t changed at all. Instead, according to foodie website Serious Eats, the nutrition consultant said that it had begun to emit “the oddest smell,” and that was really it.
It wasn’t just the burgers that didn’t seem to want to break down. New York-based photographer Sally Davies bought a Happy Meal in 2010 and snapped a photo of it daily for six months. Unsurprisingly, it looked exactly the same after a half-year – Davis said it didn’t break down, smell, or attract any insects.
These and other McDonald’s-centric experiments sent shockwaves around the world. The rumor that the food couldn’t break down on its own made its way to Iceland’s Hjortur Smarason. The chain decided to close all of its locations on the island in 2009, which gave him an idea, albeit a slightly unoriginal one.
Smarason told newswire AFP in 2019, “I had heard that McDonald’s never decompose, so I just wanted to see if it was true or not.” So he first put the burger-and-fries meal into a plastic bag and left it in his garage. There it sat for three years, and, no surprise, the food didn’t break down during that time.
So Smarason handed off the McDonald’s meal to the National Museum of Iceland. It held on to the burger and fries momentarily, but curators came to the decision that they didn’t have the resources to preserve food. In response to that, Smarason quipped, “I think he was wrong because this hamburger preserves itself.”
Smarason eventually gave the McDonald’s meal to a southern Icelandic hostel called Snotra House, where owner Siggi Sigurdur keeps the food in a glass cabinet. He told BBC News in 2019 of the burger, “The old guy is still there, feeling quite well. It still looks quite good actually.”
Sigurdur continued, “It’s a fun thing, of course, but it makes you think about what you are eating. There is no mold; it’s only the paper wrapping that looks old.” And supposedly hundreds of thousands of people from around the world want to see how the burger looks: the hostel’s webpage and burger livestream gets that many hits a day.
Of course, this wasn’t the first time that such an experiment on McDonald’s food had taken place. So it makes sense that people had come up with plenty of theories to explain the lack of decomposition. Some believed that the burgers had been pumped full of chemicals, thus preserving them for what seemed like forever.
This theory, of course, was proven to be untrue, as was the idea that McDonald’s foods simply do not rot. Instead, the explanation for the seemingly eternal burgers and fries was much more scientific. And the fast-food chain’s corporate office even released a statement to amplify this finding and quiet the unsavory ones, once and for all.
The McDonald’s meals left on display for years sat in glass containers or plastic bags, never showing even a hint of decomposition. Meanwhile, foods chucked into compost bins or dumped into trashcans and landfills start to break down quickly. But, if you think about it, these are two very different conditions in which to leave unwanted food.
Dr. Keith Warriner explained the effect that such a change in conditions could have on decay, or lack thereof. The University of Guelph’s Food Science and Quality Assurance program director took to the McDonald’s Canada’s website to break it down – pun intended. There, someone had posted a question asking the fast food chain why its meals didn’t rot.
Warriner wrote, “The reality is that McDonald’s hamburgers, french fries and chicken are like all foods, and do rot if kept under certain conditions.” The food science expert then explained that the microbes that break down and decompose our leftovers don’t work for free. Instead, they need water and nutrients to do its job.
Plus, the microbes need warmth to grow, as well as time to develop. But if you pop a hamburger into a glass case or plastic bag, you disrupt this delicate balance that would otherwise lead to decomposition. Warriner wrote, “If we take one or more of these elements away, then microbes cannot grow or spoil food.”
Warriner then turned his attention to the McDonald’s burger itself: the way the meat is fired can make it inhabitable for microbes. He explained, “In the example of a McDonald’s hamburger, the patty loses water in the form of steam during the cooking process.” Toasting the bun wicks away more moisture, he went on.
With no moisture to be found in the bun or patty, Warriner wrote, “The hamburger is fairly dry.” Place that already arid sandwich indoors – where humidity is kept low – and you have further water loss. The University of Guelph staffer continued, “In the absence of moisture or high humidity, the hamburger simply dries out, rather than rot.”
Simply put, Warriner wrote, “With moisture loss, we take away an element required by microbes to grow and cause spoilage.” But he offered ways that we could store our McDonald’s burgers that would eventually cause a breakdown – the kind we want to see in our food, anyway.
Warriner explained, “So to spoil a McDonald’s hamburger, we simply need to prevent the moisture loss. This can be done through wrapping it in cling film to prevent moisture from escaping, or storing it within a high humidity environment, such as a bathroom…” Don’t put the burger in a drier space, like a bedroom – it will never decompose.
And it’s not just McDonald’s burgers that fail to decompose without a bit of moisture present. Warriner wrote that homemade patties would suffer the same dried-out fate. He suggested, “If you try doing the same experiment with a homemade burger with similar moisture content as a McDonald’s hamburger and under similar conditions, you’ll probably get the same results.”
Luckily for you, you won’t have to try this for yourself: Serious Eats’ J. Kenji López-Alt tested the lack-of-moisture theory in a 2010 experiment for the site. He placed a homemade patty and a McDonald’s one into separate plastic bags in the hope that the container “would trap in enough moisture,” he wrote.
In López-Alt’s experiment, it took relatively no time at all for him to answer the age-old question: do McDonald’s burgers rot? The chef and writer described, “Within a week, both burgers were nearly covered in little white spots of mold…” Eventually, green and black spores took over the patties. So, clearly, the answer was a resounding yes.
And McDonald’s released a statement on August 31, 2020, to echo both Warriner and López-Alt’s findings. The company reiterated, “In order to decompose, you need certain conditions – specifically moisture. Without sufficient moisture – either in the food itself or the environment – bacteria and mold may not grow and therefore, decomposition is unlikely…”
The McDonald’s statement implored conspiracy theorists to open their eyes to the decade-old burgers that they saw online. On first glance, they may look like fresh fare from the Golden Arches, but that simply isn’t the case. Its statement said, “Look closely, the burgers you are seeing are likely dried out and dehydrated, and by no means ‘the same as the day they were purchased.’”
So you don’t have to worry about eating a McDonald’s burger and wonder how long it’ll take to break down inside of your body. Instead, as the restaurant’s statement promises, what you get is “made with only 100 percent USDA inspected beef.” So order that burger with confidence – it’s just like any other patty out there, and that’s science.