Food Mold Facts

Sometimes, people find moldy food in their kitchen, whether it’s bread that didn’t get used fast enough or forgotten leftovers sitting in the back of the refrigerator. Moldy food should usually be discarded, but a few types may be salvageable.


The mold growing on your food is a microscopic fungus with three parts. The roots, which grow down into the food, are nearly impossible to see without a microscope. The stalk rises up over the surface of the food, and the spores form on the end of the stalk. The spores are the part you see. They give mold its color, usually either green or white.

The United States Department of Agriculture estimates there could be as many as 300,000 different species of mold fungi. Alternaria, Botrytis, Neurospora and Penicillium are a few that commonly grow on food.


Mold thrives in warm, moist environments. It doesn’t require both of these conditions to grow, though, as it can form even in the refrigerator. Mold spores float through the air searching for a hospitable place to land and grow. This is why you should check for mold on food that was stored near food which has gone moldy. The spores spread rapidly from one food to another.


Some types of mold form mycotoxins, which are poisonous. They grow primarily on nuts and grains. One of the most dangerous is aflatoxin, which can cause cancer and other diseases in humans and animals. It’s most commonly found in seed corn and peanuts.

If you find mold on your food, don’t sniff it. Breathing in mold spores can cause breathing problems. Wrap the moldy food in plastic and throw it away. Wash the shelf or cupboard where it was stored, and check nearby food for signs of mold.


Many people believe they can pinch away a moldy spot on bread and the rest of it is still safe to eat. This isn’t true. The visible surface mold is only part of the mold on food. The spores have sent roots down into the food which you can’t see but which are still potentially harmful. Soft or moist food should be thrown away if it has any visible mold. Some hard foods with a low-moisture content, like cheese, salami or firm vegetables, may be safe to eat if you cut the moldy parts off.


Not all mold is bad. Some food, such as certain cheeses, are created using mold. This may be on the surface, as with Brie, or internally, as with Roquefort. The mold used for this process is safe to eat.

Some dry-cured ham develops mold on the outside. This should be wiped off, but the ham is still safe to eat.