Now, I might provide a little insight on mcdonald's burgers. The reason why people can leave them out and they supposedly never mold is because the beef which is cut into a 4inch square becomes essentially beef jerky as the sodium becomes a natural preserver. Heat from sun and light bulbs dry it out. Similar processes were used before the refrigerator was invented. The buns become stale from heat from sun preventing mold, so the burger seemingly never ages. However McDonald's burgers have been known to cause liver damage as seen from Super Size Me. I had to study this stuff for my current project
Interesting work, wish it were longer. Good luck in the future.