Answers to common questions about mold and food

When you see greenish spots on the surface of cottage cheese or a patch of fuzzy nastiness on a tomato, you know that you’re dealing with mold. But a lot of people don’t know about mold inside food—including hidden mold. And what about mold you may find growing on a piece of bread—does that mean you must throw out the entire loaf? Here are answers to the moldy bread dilemma and eight other common questions…

If I eat something moldy by mistake, how dangerous is it?

Some food molds can trigger sinusitis, asthma and allergies. Mold also can cause, in susceptible people, a host of less serious but uncomfortable symptoms, including cramps, headaches and nausea. The people who are most at risk are those with compromised immunity due to chronic illnesses (especially of the lungs), organ transplants, treatment with chemotherapy, etc.

What about the moldy yogurt scare earlier this year? Is yogurt more likely to have mold?

In September 2013, there was a recall of a popular brand of yogurt after the FDA received reports that the yogurt had mold that might have been causing cramps, diarrhea and other symptoms.

In general, if you or someone in your family has an illness that suppresses the immune system or you take medications that have a similar effect, be particularly careful with yogurt that contains fruit. Some fruits contain naturally occurring yeasts (a type of mold) that thrive in yogurt. Even if the fruit doesn’t contain these yeasts, the combination of “sugaryness” and yogurt’s soft texture creates an environment for other mold spores. It can grow overnight. Signs of mold include a swelled container…off colors or flavors…fermented or mildewy smell…and/or black or green spots.

Are any food molds deadly?

Some mold species produce poisonous substances called mycotoxins. The most dangerous of these is aflatoxin. It’s typically found in grains and peanuts, mainly in developing parts of the world. With repeated exposure, it can cause liver cancer as well as a severe form of fungal hepatitis. It’s rare in the US because manufacturers test for it constantly.

Important: If you buy a bag of peanuts and notice a moldy smell…blackened areas on any of the nuts…or a very foul taste, throw it away. You don’t want to take chances with aflatoxin.

If I cut off the moldy part, can I still eat a food?

No one likes to throw away food that has a few spots. It’s tempting to just skim or trim off small areas of mold. In general, I don’t recommend that.

Molds are filamentous organisms. They have long, threadlike structures beneath the part that you can see on the surface. The threads grow rapidly, particularly in soft foods with a high liquid content. That’s why it is much better to assume that the mold has spread throughout a container even if you can’t see it. The same goes for bread. If a slice of bread has mold, throw out the entire loaf.

Exception: It’s safe to trim the mold from hard foods, such as cheddar cheese. Cut off at least one inch around (and below) the mold spot. Be sure to keep the knife out of the mold so that it doesn’t contaminate the rest of the food.

But some cheeses are supposed to be moldy. Can these cheeses grow harmful molds on them?

Some molds taste delicious. The white coating on Brie cheese, for example, is a surface mold. Other cheeses, particularly the blue-veined varieties, such as Roquefort and Gorgonzola, are laced all the way through with mold. These cheeses are highly protected by their specific culture, and as long as they are refrigerated and sealed, they will keep without growing anything harmful for many months. But the cheese may develop a sharp, almost alcoholic, taste.

I have had honey in my cabinet for years. Why doesn’t that get moldy?

Foods such as honey that have a 50% or higher sugar content do not have enough water to grow most molds. Very salty foods, such as some preserved meats, also are unlikely to grow mold.

What’s the best way to keep mold from growing on food?

Many people think refrigeration is the best way to deter mold, but that’s actually the opposite of what you should do in many cases. Instead, store fresh foods in the same environment that they were in when you bought them. If you bought berries from the refrigerator case at the supermarket, keep them in the refrigerator at home. If you bought tomatoes at room temperature, keep them on the counter.

Exposing foods to different temperatures—and changing levels of humidity—can encourage mold growth. Also important: Buy whole, fresh produce whenever possible. The risk for mold is much higher in precut foods.

Is it true that one bad apple can spoil the bunch?

When you buy produce by the box or in large bags, you often will find at least one moldy item, usually somewhere in the middle. If you don’t get rid of it quickly, the mold will spread.

What to do: When you come home with a bulk container such as a bag of oranges, dump it out. Spread out the produce, and inspect each piece. Look for discolored or mushy areas. Throw out the bad ones.

Important: Berries are particularly susceptible to mold because they have a soft skin, plenty of moisture and contain sugar. Homegrown berries are less likely to get moldy than supermarket varieties because they’re fresher. You might want to buy berries from a farmers’ market—and buy only as much as you’ll use in the next few days.

Sometimes I see mold on the door seal of my refrigerator. Could that spread to the food inside?

Yes. Mold that grows inside the grooves of the refrigerator door seal could eventually migrate to the inside of the refrigerator. Wash the seal and the inside of the fridge with a mild bleach solution.

Also, wash the inside of crisper drawers if any moldy produce has been in them. (If gaskets on food-storage containers have mold, wash those, too.)

If food in your fridge seems to get moldy quickly, check the internal temperature of the refrigerator with a thermometer. The ideal temperature is between 35?F and 38?F.

If adjusting the temperature setting doesn’t help, you might need to repair or replace your refrigerator. If the door seal has gone bad, or if the air inside isn’t circulating the way that it’s supposed to, you might notice that your refrigerator is “sweating.” The increased moisture is ideal for mold growth.