How Does Temperature Affect the Growth of Mold on Wheat Bread?

Researched by Nichole A.


The purpose of my experiment was to determine how temperature would affect the growth of mold on honey potato bread. 

The reason I became interested in my topic was because I thought it would be helpful to find a way to keep food from molding. 

The information gathered in this experiment would help scientists who study mold and people who hate mold on their food. It will also help bread manufacturers and restaurant owners learn how to store their bread in order to keep it from molding. 


My hypothesis is that bread mold will grow at a slower rate when in a freezing temperature than it will at a warm temperature.

I base my hypothesis on a statement found on Encarta 2000 that states “storage at a low temperature slows many of the enzymatic reactions involved in spoilage and reduces the growth rate of microorganisms.” 

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The constants in this study were:
-Type of bread and the ingredients
-Date the bread was baked
-Size of bread piece
-Amount of light each piece gets
-Size of “Zip Lock” bag
-Testing procedures used
-Time at which the bread was checked 

The manipulated variable was the temperature at which the bread was stored while the experiment took place.

The responding variable was the rate of mold growth during one week of observation

I measured the amount of mold by tracing the outline of the mold onto a piece of transparent grid film covering the bread each.  Then I counted the number of square centimeters the mold covered.

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 white bread 
Zip-lock™ bags
pieces of grid film
Rhizopus stolonifer mold spores
 freezer set to -5 degrees C. (temp A)
 refrigerator set to 5 degrees C. (temp B)
room kept at about 20 degrees C. (control)
clean knife to slice the bread
 clean cutting board
breathing mask
 pair of goggles

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These are the procedures that I followed.

1. Bake bread, buy gloves and a dust mask, and order bread mold.
2. Incubate mold for seven days.
3. 5 labeled A, 5 labeled B, and 5 labeled C.
4. Label  A bags 1-5 label B bags 1-5 label C bags 1-5
5. Thoroughly clean working area.
6. Cut bread into 11 by 5 centimeter squares making sure that there is no crust on any part of the pieces.
7. Inoculate bread pieces with mold spores using a sterilized needle.
8. Place each piece of bread in a separate Zip-lock™ bag 
9. Place bags in the controlled temperatures:

  • Group A at ?5 degrees C., 
  • Group B at 5 degrees C., and 
  • Group C at 20 degrees C.
10. Check each piece every twenty-four hours and trace mold pattern on grid film and count the number of square centimeters the mold covers.
11. Transfer data from grid film to project log. 
12. Repeat steps 7 and 8 for ten days
13. Average the amount grown.

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The original purpose of this experiment was to determine how temperature would affect the growth of mold on honey potato bread.

The results of the experiment were that the mold in the freezer did not grow at all, the mold in the refrigerator grew at an average of 0.4 and the mold in room temperature grew at an average of 23.2 after seven days of sitting 


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My hypothesis was that bread mold will grow at a slower rate when in a freezing temperature than it will at a warm temperature.

The results indicate that my hypothesis should be accepted, because the mold in the freezer and refrigerator did not grow nearly as quickly as the mold in room temperature.

Because of the results of this experiment, I wonder if it would have worked better if I had sprayed the bread and used a different type of mold. 

If I were to conduct this project again I would make sure that all the bread was getting the same amount of light. I would use more bread, mold from more than one source. I would make sure that the temperature was kept more constant. I also thought that I should have used more temperatures that were between room temperature and refrigeration. I think this experiment would have worked better if I had moistened the bread.

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 It has been proven that temperature does effect the growth of mold. Freezing temperature completely stops the growth of mold.


Temperature is the difference between hot and cold. It is measured on a standard scale. It is a numeric measurement of hotness and coldness. The measurement is based on a flow of heat between two connected objects. One of the most common scales of temperature is Celsius. 
Low Temperature storage
 Low Temperature storage (LTS) is what refrigeration and freezing is called.  LTS is very effective in slowing the process of spoilage.  It also allows longer storage.  Refrigeration doesn't cause change to the food but does allow microorganisms to form after a while.  Freezing can cause chemical change if the food has not yet been frozen and it goes into the freezer before being treated.  After it has been treated it is called quick freezing.  Freezing the food before the food has been treated is called slow freezing.  Slow freezing causes the substance to leak fluids. 
 Kelvin is a fundamental physical quality that is based on the position above or below 273.16K.  It is called the triple point of water.  Kelvin is the temperature at which water, ice, and water vapor coexist together.  Zero degree k is the absolute lowest temperature at which no energy motion of molecules is made.  Kelvin is named after William Thompson, Lord Kelvin a British physicist.  He introduced this absolute thermodynamic scale in 1848.
 There are some limits as to how low the temperature can get, but as far as scientists know there isn't a limit as to how high it can get. The lowest temperature that is known is ?273.15 C.


 Mold is a multi-celled woolly growth made up of microscopic spore colonies, that lives off of dead matter, and form when contact is made with sufficient food. After landing mold attacks its “prey” with a coating of slime that helps break the food down into small partials.  Mold absorbs water and eats carbohydrates such as sugars and fats.
There are approximately one hundred thousand known species of mold and scientists think that there are as many as two hundred thousand. 

Four main types
 Penicillium is most of the blue and green molds. This particular group of molds contains an antibiotic drug, the same drug that is found in Penicillin. In fact it is what lead to the production of Penicillin. The drug found in it is so strong that inhaling it can cause severe damage to the lung. 

 Rhizopus is a type of bread mold. It is mainly the black molds. They have single tube like hyphea structures instead of many web-like structures. They are widely distributed instead of grouped together like most other molds. 

 Aspergillius are the green colored molds. There are about eighty forms of Aspergillius and over half of them are hazardous and can cause respiratory disorders. Aspergillius is one of the only types of molds that completely smothers its food. 

 Mucon is the group of white molds. There are over three hundred fifty forms of mold that fit into this group. One of the most commonly seen molds from this group is Mucor mucedo, which is a pin mold. 


Allergic Disorders
 Allergic disorders may result from an immune mechanism shut down. Antibiotics can medicate them, immediate types are more life threatening than others and can cause systematic shock. Allergies can result in hives or angiodema, a delayed reaction is a generalized rash. 

Harmful pathogens
Pathogens can harm the human body in many ways. One is through the manufacturing of toxic products (toxins) that are produced by living organisms, either exotoxins or endotoxins.  Exotoxins are released onto the surrounding area and contain extremely potential protein compounds that demonstrate selectivity with regards to the site and mode of the attack. Endotoxins are only released when the organism that produced it is broken up and only then is it harmful if eaten. 

Defense Against
 In order to defend themselves from this harm, humans and animals have developed a set of complex defense mechanisms, the most common of these systems defend the bodies eternal and external surfaces.

 In spite of defense efforts bacterial infections are often harmful or even fatal. Therefore finding other defense methods is critically important to maintaining good health


 That is a little bit about mold, the effect of temperature on mold growth and a little bit about mold related problems.

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“Aspergillus,” American Encyclopedia, 1998, vol. 2, pp. 259

Burnie, David “Mold,” Dictionary of Nature, pp. 78

Dr. Alvin, Virginia and Robert Silverstien, The Kingdom of life- Fungi, Brookfield, Connecticut, Twenty-first Century Books, 1996, pp. 30-31

“Food, Frozen,” World Book Encyclopedia, 1991, vol. 7, pp. 338-339

“Fungus,” Science Encyclopedia, Steck-Vaughn, Raintree,  1998, vol. 9, pp. 773-776

“Mold (fungi),” Encarta, 2000

“Mold,”  Science Encyclopedia, Steck-Vaughn, Raintree,  1998, vol. 13, pp. 1238-39 

“Processing and Preserving-Freezing and Refrigeration,” Encarta, 2000 


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