Bread doesn’t rot, it molds. Whether mold can grow depends on the conditions it’s kept in. The ingredients are availble to the public, the only preservative in the bun is calcium propionate which you’ll find in just about any other baked good on store shelves.
It’s not 'chemicals", it’s grease. The frying process removes almost all the water in a McDonald’s burger.
That doesn’t explain the untarnished bun.
Bread doesn’t rot, it molds. Whether mold can grow depends on the conditions it’s kept in. The ingredients are availble to the public, the only preservative in the bun is calcium propionate which you’ll find in just about any other baked good on store shelves.