From the same guy who brought you "How To Make Peking Duck At Home" comes an experiment in using hamburgers as vector for mold growth.
A bunch of websites/people have kept McDonald's hamburgers around for ill-advised amounts of time under ill-advised refrigeration conditions to demonstrate that they don't grow mold. The lack of mold is said to in turn demonstrate that said burgers are not "real food," but in fact some kind of chemical-laden horror show. Perhaps they are, but J. Kenji Lopez-Alt demonstrates that it's not chemicals that are inhibiting mold growth, but low moisture levels. It turns out that a similarly-shaped burger made at home from freshly ground beef, sans preservatives, also does not mold, whereas the larger 1/4 pound patty does grow some mold. Moisture loss rate is the difference. The regular McD's burger, and presumably the home-made version of the same (though moisture loss information was not provided for all specimens), lost moisture far faster than its larger cousin.