What Causes the Growth of Bread Mold and How to Prevent It?

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Bread Mold Growth

Bread mold is the most common type of fungus that grows on bread of any kind. Although a great source for many industrial uses, bread mold can have severe effects on the human body.

Penicillin Power!

Penicillin is the first antibiotic medication made from the fungus Penicillium chrysogenum and the credit for this discovery goes to Alexander Fleming, the great scientist.

Have you ever opened a loaf of bread that was lying in the kitchen for a long time and seen some patches of dark-colored mold on it? What happens when you leave the bread open for some more time? The mold spreads quickly and the entire bread turns into a green or black color and appears fuzzy. Bread mold is a simple fungus that takes food and nutrients from the bread and damages the bread surface. Although growth of this mold makes the bread land in the trash bin, bread mold can be of great industrial use.

Bread Mold

Mold growing on the bread can be microscopic fungi belonging to different species like Penicillium, Rhizopus, Aspergillus, Monascus and Fusarium. They are of different shapes and colors depending on the species. Rhizopus stolonifer is the most common and fast growing bread mold. It is also known as black mold as it appears dark green or black in color. It causes rotting of some fruits and some infections in humans.

Growth of Bread Mold

Microscopic parts of the bread mold fungi, known as spores, are present in the air all around us. They can be found on any surface and in any condition. They appear on the surface of bread that may be left open in normal conditions, say on the kitchen countertop. These spores germinate to form hyphae that begin to grow on the bread surface absorbing all the moisture and nutrients from the bread. With adequate nutrients from the bread they develop into mature fungi that consists of rhizoids. These rhizoids penetrate into the bread surface and hold the fungus to the organic material. It then develops fruiting structures known as sporangium, where small spores grow and are released in the surrounding areas.

Contributing Factors

Bread mold growth rate depends on several factors, temperature being the most important one. The growth rate of mildew would be slowed down, especially if the bread is kept in the refrigerator. It is observed that most molds thrive in temperatures above 70° F, and the low temperatures in the refrigerator are unfavorable for bread mold. Putting the bread slice in the freezer will stop the growth of mold completely as the temperatures in the freezer are way below the favorable temperature. As bread mold is a living organism, it requires moisture and oxygen to grow. The moisture trapped in the bag is absorbed by the fungus and it grows at a faster rate. However, as mold is a type of fungi and not a plant, bread mold does not require light for its growth.


Things Required:

  • Fresh bakery bread
  • Cotton swab
  • Dropper
  • Water
  • Resealable plastic bag
  • Adhesive tape
  • Empty milk carton
  • Disposable gloves


  1. Collect some dust from the ground with a small cotton swab.
  2. Rub the cotton swab on a slice of fresh bakery bread.
  3. With the help of a dropper, put 5 to 6 drops of water on the bread slice.
  4. Place the bread in the plastic bag and seal it.
  5. Now place this sealed plastic bag containing the bread slice in an empty milk carton.
  6. Seal the carton by using adhesive tape.
  7. Leave the carton undisturbed for two days.

What do you observe on opening the packet after two days? The bread slice is completely covered with fuzzy black or greenish spots. Dust that was put on the bread carried spores to the bread which led to the mold growth on it.


  • Moisture contributes to the faster growth of mold. Hence, do not allow your bread to turn moist. It is always better to preserve the bread that is brought from the store, in its original packaging bag.
  • If you are making bread at home, use ingredients that contain oils, like butter, eggs, milk, etc. This will allow the bread to stay fresh for longer period.
  • Breadbasket is another option for storing bread for a long time. A variety of breadbaskets made of wood, clay and metal are best for bread storage as they can keep your bread dry and moisture free.
  • Never store the bread at room temperature or in the refrigerator for extended period. Freezing will be helpful if prolonged storage is required.
  • To preserve the bread in summer needs some extra efforts. Store the bread in a plastic airtight container and if you have homemade or an unsliced bread loaf, wrap it in a wax paper and keep in a plastic container with a tight-fitting lid.
  • Lastly, make it a point to consume bread or other similar foods as fresh as possible. If you find mold growth appearing on the food, do not attempt to eat it all or in parts and dispose it off immediately.

Bread molds can be infectious and hence you should avoid touching it with bare hands. Also, molds release organic compounds like benzene and acetone that are responsible for causing headaches, dizziness and nausea. It is not necessary to be allergic to molds, anyone can react to them very easily. Take Care!

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