McDonald's Food Rots Slowly - Why?

Enterprising blogger Carrie McLaren at Stay Free! Daily ran a little experiment, and found that a McDonald's burgers and fries decomposed much more slowly than the same fare from a local diner. (Great photos of the results, in the fine scientific-method tradition of Koch and Pasteur.)

The hypothesis was that McDonald's foods have more preservatives than the food from the local joint, but a commenter presents a different one: "If the McDonald's food was not contaminated with any mold when you purchased it it wouldn't grow mold until a mold spore happen to land on the fries. In other words, it could mean that the McDonald's kitchen was cleaner than the Diner's."

As the McDonald's food is prepared at corporate factory-kitchens for final cooking at local restaurants, that could mean not only is the local restaurant cleaner, but also the upstream source. I suppose further testing is needed by honest, unbiased researchers with independent funding....

[Hat tip: boingboing]