Colorado State University Extension
SafeFood Rapid Response Network
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Molds On Food: Are They Dangerous?
Edited by: Mary Schroeder, M.S., R.D. & Pat Kendall, Ph.D., R.D., Colorado State - Spring 2004
You open the carton of cottage cheese in the back of the refrigerator only to find it covered with white mold. A half-used jar of jelly has bits of mold spots growing on it. Even the carefully wrapped chunk of cheese sports a fine covering of mold. Obviously it's time to clean out the refrigerator. But, can any of the food be salvaged?
What Are Molds?
Molds are microscopic fungi that live on plant or animal matter, and can be transported by air, water or insects. Under a microscope, they look like skinny mushrooms, consisting of three parts: thread-like roots and branches that invade the food the mold lives on, a stalk rising above the food and spores that form at the ends of the stalks. It is the spores that give mold its color. Foods that have become moldy may also have invisible bacteria growing along with the mold.
Molds are found year-round in virtually every environment and are spread through dry spores that become airborne. They grow best in warm, humid conditions, but can also grow at refrigerator temperatures. Molds can tolerate salt and sugar and can thrive on high-acid foods like jams, jellies, pickles, fruit, tomatoes, and cured salty meats such as ham, bacon, salami and bologna.
Are Some Molds Dangerous?
Yes, some molds cause allergic reactions and respiratory problems in susceptible people. A few molds produce mycotoxins, poisonous substances that can make people sick. When a food shows heavy mold growth, "root" threads have invaded it deeply. Mycotoxins are most often contained in and around these threads, but also may have spread throughout the food. Mycotoxins are produced by molds that invade grain and nut crops, but may also be found on produce, including celery, grapes and apples. The Food and Agriculture Organization (FAO) of the United Nations estimates that 25% of the world's food crops are affected by mycotoxins, the most notorious of which are aflatoxins.
Aflatoxin is a cancer-causing poison produced by certain fungi in or on foods and feeds, especially field corn and peanuts. Aflatoxins can cause illness in livestock, domestic animals and humans. They are considered unavoidable contaminants of food and feed, even where good manufacturing practices have been followed. In the U.S., the FDA and USDA monitor peanuts and field corn for aflatoxin production and can remove any food or feed with unacceptable levels.
How to Minimize Mold Growth
Cleanliness is vital in controlling mold. Mold spores from affected foods can build up in one's refrigerator, dishcloths, and other cleaning utensils. Tips to minimize molds are:
- Clean the inside of the refrigerator every few months with 1 tablespoon baking soda in one quart of water. Rinse with clear water and dry. Scrub visible mold (usually black) on rubber casings using 3 teaspoons of bleach in a quart of water.
- Keep dishcloths, towels, sponges, and mops clean and fresh. If they smell musty, they're spreading mold. Discard items you can't keep clean or laundered.
- Keep the humidity level in the house below 40%.
- Inspect grocery items such as bread before purchasing. Check food in glass jars, look at the stem areas on fresh produce, and avoid bruised produce. Notify the store manager about mold on foods!
- Examine cured meats and poultry. Exceptions: some salamis have a thin white mold coating which is safe to consume. Also, dry-cured country hams normally have surface mold that must be scrubbed off before cooking.
Precautions to Protect Food From Mold
- Process home-canned jams and jellies correctly in a boiling water bath canner for the recommended length of time at your altitude.
- When serving food, keep it covered to prevent exposure to mold spores in the air.
- Empty opened cans of perishable foods into clean storage containers and refrigerate them promptly.
- Refrigerate foods within 2 hours of preparation and serving.
- Buy food in amounts that can be used quickly. Use leftovers within 3 to 4 days, so mold doesn't have a chance to grow.
How to Handle Food with Mold on It
When you see moldy food, avoid sniffing the moldy item. Discard the food by placing it into a small paper bag or wrapping it in plastic and disposing in a covered trash can away from children or animals. Clean the refrigerator or pantry, especially in the area where the food was stored, and check nearby items that the moldy food might have touched. Mold spreads quickly in fruits and vegetables.
A handy chart with information on whether to use or discard specific foods with mold is available from the FSIS/USDA website at www.fsis.usda.gov/oa/pubs/molds.ht. In general, it's best to discard any food that has become moldy, with the possible exception of hard cheese, hard salami, dry cured ham and firm produce like carrots and bell peppers. Because it's difficult for molds to deeply penetrate these products, they can often be saved if not heavily molded. To save, cut off at least 1 inch around and below the mold spot, keeping the knife out of the mold itself to prevent cross contaminating other parts. After trimming off the mold, re-cover in fresh wrap.
For more information, contact the FSIS Food Safety Education Staff Meat and Poultry hotline toll-free at 1-888-MPHotline.
Reference: Molds on Food: Are They Dangerous? Food Safety Focus. USDA Meat and Poultry Hotline's Consumer Education and Information. April, 2002. www.fsis.usda.gov/oa/pubs/molds.htm.
