A little while ago, Grant posted about an experiment being conducted by artist Sally Davies. She left a Happy Meal out, and took a picture of it every day. And, somewhat alarmingly, it didn’t decay.
Well, another intrepid soul decided to take it upon himself to conduct a little experiment of his own. J. Kenji Lopez-Alt at Serious Eats figured there was probably an entirely rational (and scientific!) reason for the Happy Meal not turning into a pile of smelly, moldy grossness.
What he decided to do was make his own burgers, and leave all of them out. Here are the variations he experimented with:
- Sample 1: A plain McDonald’s hamburger stored on a plate in the open air outside of its wrapper.
- Sample 2: A plain burger made from home-ground fresh all-natural chuck of the exact dimensions as the McDonald’s burger, on a standard store-bought toasted bun.
- Sample 3: A plain burger with a home-ground patty, but a McDonald’s bun.
- Sample 4: A plain burger with a McDonald’s patty on a store-bought bun.*
- Sample 5: A plain McDonald’s burger stored in its original packaging.
- Sample 6: A plain McDonald’s burger made without any salt, stored in the open air.
- Sample 7: A plain McDonald’s Quarter Pounder, stored in the open air.
- Sample 8: A homemade burger the exact dimension of a McDonald’s Quarter Pounder.
- Sample 9:A plain McDonald’s Angus Third Pounder, stored in the open air.

He found that the burgers roughly the same size as the Happy Meals did not rot. The larger Quarter Pounder-sized ones, however, did.
Why? Because mold needs moisture to grow. And the tiny burgers just didn’t have any. From Lopez-Alt’s conclusion:
So there we have it! Pretty strong evidence in favor of Theory 3: the burger doesn’t rot because it’s small size and relatively large surface area help it to lose moisture very fast. Without moisture, there’s no mold or bacterial growth. Of course, that the meat is pretty much sterile to begin with due to the high cooking temperature helps things along as well. It’s not really surprising. Humans have known about this phenomenon for thousands of years. After all, how do you think beef jerky is made?
Now don’t get me wrong—I don’t have a dog in this fight either way. I really couldn’t care less whether or not the McDonald’s burger rotted or didn’t. I don’t often eat their burgers, and will continue to not often eat their burgers. My problem is not with McDonald’s. My problem is with bad science.
For all of you McDonald’s haters out there: Don’t worry. There are still plenty of reasons to dislike the company! But for now, I hope you’ll have it my way and put aside your beef with their beef.
(via)