What Causes Mold in Bread?

Updated April 17, 2017

Many people prefer to keep bread at room temperature, but refrigeration means you won't have to throw out as much bread due to mould. Mold is caused by several factors.


Millions of invisible mould spores inhabit the air around you. These spores swirl around in the dust in your home. When you leave bread out or the refrigerator open for any amount of time, mould spores float onto your bread.


Mold belongs to the fungi family. Fungi contain no chlorophyll, so it can't draw energy directly from the sun. Instead mould fungi derives nutrients from other food sources. The ingredients in bread, along with a low moisture index, create the perfect environment for the mould to settle on, grow and reproduce.

Warmth & Nutrients

Mold thrives in warm, moist conditions which is why bread that is not refrigerated will show signs of mould before bread in the refrigerator. Mold eventually will grow on bread that is refrigerated because the bread provides a good source of nutrients for the mould spores. However, the colder temperatures do retard the growth of mould on bread.

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About the Author

Carolyn Scheidies has been writing professionally since 1994. She writes a column for the “Kearney Hub” and her latest book is “From the Ashes.” She holds a Bachelor of Science in journalism from the University of Nebraska at Kearney, where she has also lectured in the media department.