Some molds are an integral part of the food on which they grow, like the mold that makes blue cheese or the white mold that forms a thin layer on the outside of hard salami. But mold in the refrigerator can be dangerous; such molds ruin food and can cause negative health effects ranging from allergic reactions to cancer.
Mold on Foods in the Refrigerator
Since some mold is dangerous to human health, with a few exceptions, you should discard any food in the refrigerator with visible mold. Grains, nuts and produce all can support the growth of mycotoxins, which sicken people. One group of mycotoxins is aflatoxins, which are poisonous and can cause cancer.
In the case of hard cheese and firm vegetables or fruit, it's usually safe to cut away the mold along with an inch of the surrounding food and use what's left if the mold is not extensive. A coating of mold on ham and hard salami is normal; the meats are safe to eat once you scrub it away.
Mold on the Refrigerator Itself
Mold spreads by airborne spores, so moldy food in the fridge may eventually lead to mold growing on the appliance itself. Clean mold from the inside of the refrigerator by scrubbing it with a solution of 1 tablespoon of baking soda mixed with 1 quart of water and rinsing with plain water. Mold can also grow on the rubber seals around the door; remove it with 1 tablespoon of chlorine bleach mixed with 1 quart of water.
How Mold Grows
Almost everyone is familiar with the blue, green, gray or black fuzz that signifies mold growth. What many don't realize is that surface mold is basically the "seed head" of an organism growing deep beneath the surface. Molds are not plants, but you can visualize them as having roots reaching into the food, stalks growing above the surface and spores, which act like seeds, growing at the top of the stalk. These deep roots may infiltrate soft foods even where surface mold is not visible.
Preventing Mold Growth
Mold spores spread through the air, on insects and by surface-to-surface contact. Covering food in the refrigerator helps prevent airborne contamination. If food is already moldy, resist the temptation to smell it or you could inhale mold spores, possibly resulting in an allergic reaction. Wrap the moldy food in plastic and put it in a covered trash can. Clean the area where the food was stored. Don't use musty dishcloths or sponges on the refrigerator; they spread mold spores even as you are trying to clean.