Leafy Greens

"If the leaves still look firm and there's no visible deterioration of the leaf tissue, you can still use them," Worobo says. When it comes to salad leaves, common signs of spoilage include wilting, sliminess, foul odor, or change of color, says Havern. "You should also check the bottom of the bag, because spoilage may occur at the bottom of the bag first," says Worobo. Most notably, spoiled leaves will produce an off-colored liquid, which often accumulates at the bottom.

Sources: How to Store Bagged Salad So It Stays Fresh, According to Food Scientists