"Bacterial growth is time and temperature dependent" said Eileen Dykes of the USDA Meat and Poultry Hotline.
Dykes recommends a time limit of two hours between meal to fridge transport, which is not always enough time "if you go to a restaurant and then get a doggy bag, and then go to a movie."
Watching a thermometer in the fridge and counting days on the calendar does far better for home food safety than searching for funny smells or sites of mold. But that doesn't mean those disgusting signs are useless.
Without a thermometer or a clue about the time since purchase, Donnelly says those signs of spoilage can help.
"Depend on those spoilage clues," Donnelly said. "Because it can mean that something else has been growing there."
But mold is a different story. Most mold that grows on bread or fruits isn't toxic, according to M. A. Cousin, a food microbiology and mold expert at Purdue University.
"But if somebody is allergic to mold, and you would inhale those molds, it may give them an adverse reaction," Cousin said.
Otherwise, the allergy-free consumer can just cut a few inches past the mold and the allergy-free consumer will be fine.
"You have to realize that everyone's perception of spoilage is not the same because all of us have different senses; we don't have the same taste, smell, or even see it the same way," Cousin said. "That's why two people don't always agree -- some people would eat it, other people won't."
If you still have questions about the safety of meat or poultry, an expert can assist you at the USDA meat and poultry hotline at 1-888-674-6854.