Mold is a type of tiny fungus. There are thousands of different kinds. They are often seen in wet places. Molds include all species of microscopic fungi. In contrast, microscopic fungi that grow as single cells are called yeasts.

Some molds cause disease or food spoilage. Sometimes people use them to make some kinds of cheese and antibiotics. One special kind of mold can be used to make penicillin, a common antibiotic.

For significant mold growth to occur, there must be a source of water (which could be invisible humidity), a source of food and a substrate capable of sustaining growth. Common building materials, such as plywood, drywall, furring strips, carpets, and carpet padding are food for molds. In carpet, invisible dust and cellulose are the food sources. After a single incident of water damage occurs in a building, molds grow inside walls and then become dormant until a subsequent incident of high humidity; this illustrates how mold can appear to be a sudden problem, long after a previous flood or water incident that did not produce such a problem. The right conditions reactivate mold. Studies also show that mycotoxin (a toxic chemical produced by mold) levels are perceptibly higher in buildings that have once had a water incident.

Harvested foods decompose from the moment they are harvested due to attacks from enzymes, oxidation and microorganisms. These include bacteria, mold, yeast, moisture, temperature and chemical reaction.

Signs of food spoilage may include an appearance different from the food in its fresh form, such as a change in color, a change in texture, an unpleasant odor, or an undesirable taste. The item may become softer than normal. If mold occurs, it is often visible externally on the item.

Five mycotoxins have been reported to be associated with molds found in fermented meats.

See also:
Mold
Food Spoilage

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