Bread mold is a type of fungi. Fungi can be divided into two morphological forms. Unicellular fungi reproduce asexually by budding or fission. Multi-cellular fungi reproduce both asexually and sexually. Most bread molds are multicellular and occur in the form of hyphae. Common types of bread mold include Aspergillus, Penicillium and Rhizopus.
Mold exists everywhere as the air is filled with tiny molds spores. Bread easily gets moldy because it provides a good source of food for the fungi. When a spore lands on the food, a hypha grows out from it. The hypha grows and branches again and again, forming mycelium, a network of hyphae, until the mycelium covers the surface of the food. The hyphae digest nutrients in the bread by secreting digestive enzymes onto the food, breaking it down into soluble substances such as sugars. Then the hyphae absorb these substances by absorbing them, and then store some of these kinds of food as glycogen. When the food is used up, the mold spreads to infect another source of food.
Fungi reproduce quickly, and some of them can even double their mass every hour, until all available nutrients are digested and absorbed. They reproduce by means of spores and this will be further discussed in the next section.
The spores can be destroyed by cooking, and this explains why freshly baked bread does not get infected with molds immediately. In addition, organic bread tends to grow molds faster because there are no preservatives in it. A warm, moist, and dark environment is most suitable for mould to grow.