Exposing the Myth: McDonald’s food doesn’t rot?

On February 3, 2016 a woman posted a picture of McDonald’s food that was six years old and had not rotted. The firestorm that followed involved claims of harmful chemicals in food, that McDonald’s food was poisonous and bad for you (I should note that McDonald’s food does taste terrible, but it’s not poison) and of course, claims about GMOs. But the issue is that McDonald’s food not rotting is nothing new and it doesn’t prove anything. As always there is a rational, science based explanation for it.

I’m not sharing the image directly here because i don’t know if she’s made it publicly available and, although I think a case could be made for fair use in this instance, I am a firm believer in intellectual property rights. But you can follow the link and view the images for yourself.

As you’ll see, the receipt does state that the food was purchased 6 years ago, February 8 2010. Lets leave aside the obvious possibility that this is a faked story (i.e. a legitimately 6 year old receipt taped onto freshly purchased food) and tackle the real issue at hand: does McDonald’s food really not rot?

Yes, McDonald’s food really doesn’t rot in certain conditions, frying being one of them.

I should point out that the burger is not visible in the picture, although there have been instances of burgers not rotting as well, which I’ll get into later. But if you take a look at the two food items, the french fries and the chicken nuggets, you’ll see that, with a little bit of food knowledge it’s perfectly reasonable to not see any rot on them, even after 6 years.

Both items are deep fried, which as cooking methods go is a dry process. Oil itself is hydrophobic and cooking done with submersion in oil is a waterless (dry) cooking method. In fact, it will dry out your food even though it makes it taste moist. As you can see, the food itself is already protected against moisture in the cooking process.

In addition, cooking in oil will sterilize almost any food product unless it has some nasty bacteria or spores on it. These two factors are what’s really contributing to the lack of rot, not “chemicals”.

Why is this important? Because rot is a function of bacteria and mold, both of which require moisture to grow. For example, if we launched a hamburger (or any organic matter) onto the moon it would be preserved in pristine condition because there is no moisture in space (and also any residual moisture in the food would freeze). The same effect is happening here. The frying method used to cook the food helps prep the food to be as dry as possible, simultaneously killing any pathogens on the food. The heat of the items also helps evaporate any residual water that was present on the food. What we have here is food that has been fried and dried, and stored in a moisture poor environment.

I’m sure that, if a lab were to look at the food in question, they’d find loads of bacteria and fungi spores just waiting to grow if only they got the required water to do so. They simply landed on the food in the following 6 year wait and found a dry wasteland inhospitable to their growth.

This phenomenon is nothing new. McDonald’s itself even addresses it on their website, stating:

Actually, it can [rot]. Food needs moisture in the air for mold to form. Without it, food will simply dry out — sort of like bread left out on a counter overnight to make croutons for stuffing.

You might have seen experiments which seem to show no decomposition in our food. Most likely, this is because the food has dehydrated before any visible deterioration could occur.

Funny that they mention “you might have seen experiments” because these claims are nothing new. In fact, I think the record is a burger purchased from McDonald’s in 1996 which still looks fresh (but is certainly not edible).

Serious Eats did a science experiment to test this hypothesis. Their results, yes the McDonald’s burger does appear not to rot over time. As do a lot of other burgers. In fact, a burger made of home ground meat (presumably without any additives) also failed to rot. Oddly enough there were two burgers that did rot: a quarter pounder burger from McDonalds, and samples of burgers stored in ziploc bags.

Why would these two burgers rot but the other (smaller) burgers not? The answer, is moisture. It should be fairly obvious that the burger in the ziplock bag wasn’t able to dry out because of the plastic locking moisture in. As far as the quarter pounder, we have surface area to blame. The larger burger, with larger surface area, takes more time to dry out than a smaller, kids meal burger. Hence, the quarter pounder rots and the kids meal burger doesn’t because it dries out sooner.

Here we have two examples of “experiments”, one pseudoscientific (no controls, no reproducibility, no attempt to remove possible confounds) and one scientific (controlling for size of burger, manufacturing process, storage medium). Sadly, social media is exploding right now with this supposed proof that “McDonald’s food has poisonous chemicals that doesn’t make food rot!”

Which, even if it were true, wouldn’t that be good? That’s the whole reason why we use preservatives, so that our food will last and we won’t be wasting our money buying food we never get the chance to eat. Not that I’d recommend eating a years old (or even days old) burger: there certainly are dangerous bacteria and spores present that, once placed in the hospitable climate that is your gut, will bloom and possibly kill you.

Again, don’t believe everything you see on social media. There usually is a rational, scientific reason for it.

Media Credit

The featured image used for this article is “The McDouble” by Evan-Amos via Wikimedia Commons. It is available under a Creative Commons Attribution-Share Alike 3.0 Unported license.