While mold in the form of blue cheese is safe for consumption, you should assume that any mold on bread is harmful and avoid eating it. Moldy bread can make you sick or lead to breathing problems if you have a mold allergy.
What to do with bread once you notice mold on it is a common household dilemma. You want to be safe but not needlessly wasteful.
You may wonder whether the fuzzy spots of mold are safe to eat, can simply be scraped off, or whether the rest of the loaf is safe to eat if it doesn’t have visible mold.
This article explains what mold is, why it grows on bread, and whether it’s safe to eat moldy bread.
Mold is a fungus in the same family as mushrooms. Fungi survive by breaking down and absorbing the nutrients of the material on which they grow, such as bread.
They’re what gives mold its color — white, yellow, green, gray, or black, depending on the type of fungus.
However, you can’t identify the type of mold by color alone, as the color of the spots may change under different growing conditions and can fluctuate during the lifecycle of the fungus (
Types of mold that grow on bread include Aspergillus, Penicillium, Fusarium, Mucor, and Rhizopus. What’s more, there are many different species of each of these types of fungus (
Mold is a fungus, and its spores appear as fuzzy growths on bread. Many different types may contaminate bread.
Some mold is safe to consume, such as the types purposely used to make blue cheese. However, the fungi that can grow on bread give it an off-flavor and may be harmful to your health.
It’s impossible to know what kind of mold is growing on your bread just by looking at it, so it’s best to assume it’s harmful and not eat it (1).
Additionally, avoid smelling moldy bread, as you may inhale spores from the fungus. If you have an allergy to mold, inhaling it could lead to breathing problems, including asthma (1).
Lastly, people with weak immune systems — such as from poorly controlled diabetes — are vulnerable to infection from inhaling Rhizopus on bread. Though uncommon, this infection is potentially life-threatening (
Mold gives bread an off-flavor, may trigger allergic reactions and may cause harmful infections — particularly if you have a weak immune system. Therefore, you should never knowingly eat or smell it.
The Food Safety and Inspection Service of the United States Department of Agriculture (USDA) advises discarding the entire loaf of bread if it has developed mold (1).
Though you may only see a few spots of the fungus, its microscopic roots can spread quickly through porous bread. Therefore, don’t try to scrape off mold or salvage the rest of your loaf.
The USDA advises discarding the entire loaf of bread if it has developed mold, as its roots can quickly spread in your bread. Additionally, some types of fungi produce harmful toxins.
Without preservatives, the shelf-life of bread stored at room temperature is generally three to four days (
Preservatives and other ingredients, as well as certain methods of handling and storing bread, may deter mold growth.
Ingredients That Inhibit Mold
Still, a growing number of people prefer bread with cleaner ingredients, meaning bread made with no chemical preservatives (
Bread Handling and Storage Tips
Common mold spores generally can’t survive baking, but bread can easily pick up spores from the air after baking — for example, during slicing and packaging (
These spores can start to grow under the right conditions, such as in a warm and humid kitchen.
- Keep it dry. If you see visible moisture inside the bread package, use a paper towel or a clean cloth to dry the package before sealing it. Moisture encourages mold growth.
- Cover it. Keep bread covered, such as when serving it, to shield it from spores in the air. However, to avoid soggy bread and mold, don’t package fresh bread until it’s thoroughly cooled.
- Freeze it. Though refrigeration slows mold growth, it also makes bread dry. Freezing bread stops the growth without altering the texture as much. Separate the slices with wax paper to make it easier to thaw only what you need.
Some bread is protected with special packaging instead of preservatives. For example, vacuum-sealing removes oxygen, which is needed for mold growth. Still, this bread is prone to contamination after you open the package (
To inhibit mold growth, chemical preservatives are typically used in bread. Without them, bread generally starts to grow the fungi within three to four days. Freezing bread prevents the growth.
You shouldn’t eat mold on bread or from a loaf with visible spots. The mold roots can quickly spread through bread, though you can’t see them.
Eating moldy bread could make you sick, and inhaling spores may trigger breathing problems if you have a mold allergy.
Try freezing bread to prevent mold.