Dr. Roberts explains that onions naturally want to be dry - which a refrigerator is not.
"When you stick them in a refrigerator, you introduce moisture, and so what happens is they start to mold. When they mold, they become soft," she says.
She says refrigeration causes a chemical reaction in potatoes that will make them rot faster - and change their flavor.
"This is a starch. You put a starch in the cold and what it does is it starts to convert to sugar," she explains.
"It's just criminal to put that guy in the refrigerator because you're just destroying him!" Roberts laughs. She says cold causes the tomato's cell walls to break down, causing them to get mushy.
Roberts says many people think, "'Tomatoes were so good when my grandma made them, and now they're terrible!' That's not true, it's because your grandma knew not to put them in the refrigerator," she says.
Some people keep bread in the refrigerator thinking it will last longer cool, when actually the icebox accelerates staleness.
"One day in the refrigerator is equivalent to three days at room temperature," she says. She adds most breads say right on the bag to keep at room temperature.
A few other tips from Roberts?
Milk spoils faster on the door so you should keep it on the shelf instead, and to pitch leftovers after 48 hours regardless of what the content is.