There's been speculation that the meat was pumped full of chemicals and sodium propionate, but Lopez-Alt wanted an objective test, so he set up an informal experiment . He left the burger out, unwrapped, and he also made his own burger out of ground chuck, salted and cooked it (just like McDonald's), and put it on a store-bought bun and left that out, too.
What happened? It turns out that neither burger decayed .
So there you have it, meat and heat goes a long way in preserving things. Whether this means you should go out to Mickey D's or challenge some long held assumptions about leaving meat lying around your house is entirely up to you. Personally, I would recommend either checking out this recipe or reading another great post from The Food Lab .
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