Is the Food in Your Fridge Safe to Eat?

With three children, food doesn't last long in the Stanisci household in New Jersey.

"I must shop probably two to three times a week for food," said mom Kathy Stanisci.

But she admits that despite her frequent trips to the store, some items in her kitchen might have outlived their shelf life.

"Good Morning America" Weekend Edition asked Dr. Michael Doyle, director of The Center for Food Safety at The University of Georgia, to look through the Staniscis' refrigerator to see which items are still edible and which ones should be thrown away.

Doyle's first concern was the Staniscis' deli turkey, which was six days old. He brought it back to his lab and found hundreds of thousands of bacteria.

"I would consider [this] getting close to spoilage," he said.

He recommends keeping deli meats a maximum of four days.

"Buying meats at the deli counter can sometimes be a bit riskier than if you were to buy meats that are already prepackaged by a processor, because the processor will, in the process, heat-treat the meats and treat them in such a way that the bacterial counts are very, very low," Doyle said.

Spoilage Can Be Deceiving

The Staniscis' expired eggs, on the other hand, were fine. Doyle said that commercially-sold eggs are treated with a disinfectant that keeps bacteria counts low.

Pasteurized milk is also resistant to bacteria. It might start to taste bad after a week or two, Doyle said, but it won't harm you.

Mayonnaise is made with bacteria-killing vinegar, so it's safe in the fridge for a year -- same with ketchup.

But Doyle found a heavy load of bacteria on the Staniscis' half-eaten, two-week-old package of salad mix, even though it looked fine.

"Once you've opened a bag of lettuce, it's important to consider that bag as now ready to eat because you've now exposed it to an environment where you might have bacteria entering it," Doyle said.

As for the leftovers, Doyle found that the chicken and string beans Stanisci had made just one night before had tens of thousands of bacteria. But her three-day-old Chinese takeout and five-day-old cheese pizza had relatively low bacteria counts.

"Not all leftovers are created equal," Doyle said. "So, my rule of thumb is, if it's a highly perishable type of food, like a cooked meat product, three to four days should be the maximum."

Contrary to popular belief, Doyle said, items like plastic wrap, aluminum foil and Tupperware may make your foods taste fresher but they won't extend their shelf life. And when it comes to mold, if you find it on a brick of cheese, just cut that chunk off. But if you find it on a slice of bread, the whole loaf has to be thrown out because invisible mold may have spread to the other slices.

Perhaps the single best thing you can do to extend the shelf life of your foods is to make sure your refrigerator is set at 40 F or lower.

"I've seen home refrigerators as high as 55 degrees Fahrenheit! That is no longer a refrigerator," Doyle said. "We microbiologists call that an incubator. That's how you grow bacteria."

ABC's Nancy Weiner reported this story for "Good Morning America Weekend Edition."