By now, I suspect that almost everyone will have seen the videos of burgers and fries from McDonald’s taking a suspiciously long time to rot. The suggestion is that McDonald’s packs tons of chemicals and artificial preservatives in their products to prolong their shelf life, incidentally also making them very harmful to eat. The Burger Lab, a food blog who was also behind a massive effort to deconstruct the precise composition of McDonald’s fries and make them at home, has punched a hole in this theory.

After an extensive series of tests, he finds that, yes, McDonald’s burgers do indeed take much longer to rot than other burgers, but the reason isn’t due to chemical preservatives. It is primarily due to the large surface area of the burger compared to its volume, causing it lose moisture rapidly. Since the meat is sterile to begin with, this makes it very hard for mold spores in the air to establish a foothold. To further prove his point, he performed another experiment in which the burger was stored in a plastic bag designed to retain moisture, and found that the McDonald’s burger does indeed rot normally in this case. Check out his extensive blog post for more details.