It's happened to all of us: That fresh peach you were so excited to eat is suddenly sporting a dime-sized fuzzy, white growth. Or your last slice of sandwich bread has sprouted a few tiny flecks of green. Is it safe to just trim off the unappealing area and consume the rest?
Mold on the surface of food usually appears as a white or green area, often fuzzy in texture [source: Payne]. It can be widespread or appear to be isolated on just one section. And while it may look like the growth is only on the surface, mold is a fungus with a structure similar to a plant – roots, a stalk and spores. The roots, often invisible to the naked eye, can grow quite deep. The stalk and spores are what you see on the surface. The spores can become airborne, which is what causes the mold to spread on the current object, as well as contaminate neighboring foods [source: USDA].
You've heard the expression "One bad apple spoils the barrel"; often if mold develops on one piece of food, it quickly spreads to the other nearby food.
Not all molds are bad, and some are normal parts of a food. Some cheeses, such as Roquefort, are speckled with characteristic blue-green "veins." To achieve this quality, cheesemakers introduce a healthy, edible type of mold during the manufacturing process. The resulting cheeses are perfectly safe to eat, uniquely creamy and quite popular – although admittedly boasting a funky acquired taste [source: Rebuffet-Broadus].
But other molds can cause problems. Some cause allergic reactions or induce respiratory distress, which is why you shouldn't sniff at a moldy product. And some molds produce poisonous substances called mycotoxins, which can cause serious illness [source: Payne].
So what about that tasty peach you were looking forward to? Because of its soft texture and high moisture content, it's likely that further invisible contamination exists beyond just the visible surface mold. It's safer to send that item to the compost bin rather than risk illness.
For complete, up-to-date guidelines on what food is safe and what isn't, visit the USDA's website. But what follows here is a quick summary of important points about which moldy foods to toss and which to trim.
While not all moldy foods have to be sent directly to the garbage pail, there are some that should not be consumed. This typically applies to most foods that are soft and moist, because the mold may be growing deeper into the product than it appears. For instance, toss these items if you see mold: lunch meats, bacon, hot dogs, cooked casseroles, cooked grains or pasta, peanut butter, legumes, nuts, soft cheeses, yogurt and sour cream [source: USDA].
Jams and jellies should also be discarded at the first sign of mold, as they may contain mycotoxins. Finally, moldy baked goods and breads should also be tossed – no more trimming the crust off that last slice of sandwich bread [source: USDA].
While moldy cold cuts and lunch meats should be discarded, hard salami and dry-cured ham are an exception; for these items, you can safely scrub the surface, removing the mold completely [source: USDA].
For hard cheeses and hard fruits and vegetables, the food can be consumed after you trim away the mold. Be sure to trim at least 1 inch (2.51 centimeters) around the offending area, and take care to stop using and clean the knife if it contacts the mold, as that can cause cross-contamination [source: USDA].
It may be disappointing to toss out whole products, but it's always better to err on the side of caution.