Friday, November 5, 2010

Why don't McDonald's burgers rot?

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...

[T]here are a number of theories as to why a McDonald's burger might not rot:
  1. There is some kind of chemical preservative in the beef and/or bun and/or the wrapping that is not found in a normal burger and/or bun that creates an inhospitable environment for mold to grow. ...
Theory 1 is the one most often concluded in the various blogs out there, but there doesn't seem to be strong evidence one way or the other. ...

I decided to design a series of tests in order to ascertain the likeliness of each one of these separate scenarios...

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. ...

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.
--J. Kenji Lopez-Alt, A Hamburger Today, on vindication for McDonald's. HT: Chris Blattman

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