When Things Get a Little Moldy

By Diane Wright Hirsch, MPH, RD
Extension Educator/Food Safety

I still have some locally grown tomatoes sitting on my kitchen counter. I went away for a week and they still look fine, no mold. I guess I picked out some good ones. At this time of year as we search the farmer's markets for the last of the home-grown tomatoes or fresh local apples or even, if you are very lucky, an ear of corn, it is important to choose those with no sign of rot or mold.

As time goes on and the weather is less amenable to growing, our choices of local produce are often limited to winter squashes, potatoes and cabbages, which store well in the proper environment well into the middle of winter. But, sometimes, even under the best of conditions, we find that some of the late season produce may too quickly show signs of rot and mold growth. Many of us were raised to believe that a little mold is harmless and that simply by cutting it off, we could eat the remainder of the food without a thought or concern about the safety of that food. I still remember, after carefully removing the paraffin wax from my Mom's homemade strawberry jam, scooping off the mold and spreading the "mold-free" jam on my toast.

As it turns out, that might not have been the smartest thing to do. Why?

The mold that you can find on food is not really as harmless as most of us think it is. Sure, some molds are actually used to MAKE food. Particularly, blue veined cheeses such as Roquefort, are produced by the introduction of Penicillium roqueforti spores. These molds are seen throughout a block of blue cheese. Surface molds are used to make Brie and Camembert.

But, on the other hand, some molds can cause allergic reactions while others can produce mycotoxins under the right growing conditions. These toxins or poisons can make you sick: some are thought to be cancer-causing or cancer-promoting. One example is aflatoxin, produced by a mold (Aspergillus flavus) that may be found on field corn or peanuts. Patulin is a mycotoxin produced by a variety of molds, particularly Aspergillus and Penicillium found on apples and pears.

Other mycotoxins may simply cause an upset stomach and diarrhea. Some readers may remember learning about the Salem witch trials in 1692. One theory that has been suggested to explain the strange behavior of some of Salem's residents was published in the magazine, Science, in 1976. The article blamed the strange behaviors of those accused of witchcraft on the fungus ergot, which can be found in rye, wheat and other cereal grasses. Eating ergot-contaminated foods may result in delusions and hallucinations similar to the effects of LSD. Muscle spasms and vomiting could also result. This fungus thrived in the humid environment of coastal Massachusetts where rye was grown.

Some molds are likely to be harmless if ingested. But, since most people do not have the ability to distinguish between harmless types of mold and those that can make you sick, the best advice is to avoid mold and foods that are significantly affected by mold.

Molds are microscopic fungi that live on plants. There may be as many as 300,000 species of these fungi. They are threadlike (filamentous) organisms that produce spores as a way to multiply. When mold grows, it produces many cells which can often be seen by the naked eye (unlike bacterial cells that require a microscope). The fungi often consist of stalks and spores that are seen on the surface of the food. In addition, there are root threads and branches that grow into a food. These are difficult to see. It is easier for these threads to penetrate foods that are soft in nature: jams, jellies, cottage cheese and tomatoes are examples. You are unlikely to see how far the mold has spread into the food.

So, what should you do with that moldy tomato or cabbage? The United States Department of Agriculture (USDA) recommends that you:

• Examine food well before you buy it and/or eat it. Look at the stem areas on fresh produce, and avoid bruised produce.
• Don't sniff the moldy item. This can cause respiratory trouble. And those who are allergic to molds might have a reaction to the mold.
• No matter what kind of food it is, if it's covered with mold, discard it. Put it into a small paper bag or wrap it in plastic and dispose in a covered trash can that children and animals can't get into.
• Clean the shelf, bowl or refrigerator at the spot where the food was stored.
• Check nearby items the moldy food might have touched. Mold spreads quickly in fruits and vegetables.

Specifically,

• If you find mold on jam, discard it. The mold could be producing a mycotoxin. Microbiologists recommend against scooping out the mold and using the remaining condiment. (And, if you can your own jams and jellies, be sure to sterilize your jars before filling, use 2 piece screw band lids, and process all jams and jellies in a water bath canner for at least 5 minutes.)
• For firm fruits and vegetables such as cabbage, bell peppers, and carrots, you can use them if they have a little bit of mold on them. Cut off at least 1 inch around and below the mold spot (keep the knife out of the mold itself so it will not cross-contaminate other parts of the produce). Small mold spots can be cut off fruits and vegetables with low moisture content. It's difficult for mold to penetrate dense foods.
• For softer fruits and vegetables such as cucumbers, peaches and tomatoes, it is best to discard any with any mold on them. Fruits and vegetables with high moisture content can be contaminated below the surface.

You may find more information about mold and how it affects the safety of meat, bread, grains and other foods as well as fresh produce at the web site of the USDA, www.fsis.usda.gov/Fact_Sheets/Molds_On_Food/index.asp. Some background on the Salem witch trials and the theory of how mold toxins may have contributed may be found at http://www.smithsonianmag.com/history-archaeology/brief-salem.html?c=y&page=1, used as a source for this article.

For more information on home gardening topics and food safety, contact the University of Connecticut Home and Garden Education Center at ladybug@uconn.edu or 1-877-486-6271.