Although reports about the risks of eating moldy food arent new, a recent bulletin from the USDA Food Safety and Inspection Service strongly cautions consumers about the dangers, warning that some molds on food can cause allergic reactions and respiratory problems. And a few molds, in the right conditions, produce mycotoxins, poisonous substances that can cause illness. These molds are found primarily in grain and nut crops, but are also known to be on celery, grape juice, apples and other produce.
Molds are microscopic fungi that live on plant or animal matter. Unlike bacteria that are one-celled, molds are made up of many cells and can sometimes be seen with the naked eye. Under a microscope, they look like skinny mushrooms.
In many molds, the body consists of: root threads that invade the food it lives on, a stalk rising above the food, and spores that form at the ends of the stalks. The spores give mold the color you see. When airborne, the spores spread the mold from place to place like dandelion seeds blowing across a meadow.
Molds have branches and roots that are like very thin threads. The roots may be difficult to see when the mold is growing on food and may be very deep in the food.
Foods that are moldy may also have invisible bacteria growing along with the mold. You see only part of the mold on the surface of food - gray fur on forgotten bologna, fuzzy green dots on bread, white dust on cheddar, coin-size velvety circles on fruits, and furry growth on the surface of jellies.
When a food shows heavy mold growth, "root" threads have invaded it deeply. In dangerous molds, poisonous substances are often contained in and around these threads. In some cases, toxins may have spread throughout the food.