Turns out ANY hamburger with a small patty like McDonalds burgers won't rot. One person tried 9 different burgers (including home made ones) to confirm this.
Sample 1: A plain McDonald's hamburger stored on a plate in the open air outside of its wrapper.
Sample 2: A plain burger made from home-ground fresh all-natural chuck of the exact dimensions as the McDonald's burger, on a standard store-bought toasted bun.
Sample 3: A plain burger with a home-ground patty, but a McDonald's bun.
Sample 4: A plain burger with a McDonald's patty on a store-bought bun.*
Sample 5: A plain McDonald's burger stored in its original packaging.
Sample 6: A plain McDonald's burger made without any salt, stored in the open air.
Sample 7: A plain McDonald's Quarter Pounder, stored in the open air.
Sample 8: A homemade burger the exact dimension of a McDonald's Quarter Pounder.
Sample 9:A plain McDonald's Angus Third Pounder, stored in the open air