How Does the Type of Cheese Affect Mold Growth

Researched by Jacob
1999-2000



Purpose

The purpose of this experiment was to compare the amount of mold growth on three types of cheese (American, Swiss, and cheddar).

I became interested in this idea when I found mold all over the cheese in our refrigerator and was concerned because we had just bought the cheese.   I wanted to find which cheese to buy to avoid repeating the problem. 

The information gained from this experiment would help people know which cheese to buy for long term use. 


Hypothesis

My hypothesis is that American cheese will support more mold growth than the other varieties. 

I base my hypothesis on World Book Encyclopedia, which says, "The more moisture the cheese has, the softer it is."  This means soft cheese is moist and moisture is what mold needs to grow according to many books I read.  American cheese is the softest out of American, Swiss, and Cheddar. 
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Experimental Design

The constants in this study were: 

  • The amount of cheese. 
  • The storage of cheese slices in individual zip-lock bags. 
  • The kind of mold used to inoculate the cheese. 
  • The amount of mold spores inoculated on the cheese. 
  • The temperature, light, and humidity in the incubation environment. 
The manipulated variable was the type of cheeses. 

The responding variable was the rate the mold grew on the cheese.

To measure the responding variable I used a transparent grid sheet to determine the approximate number of square centimeters of mold on the cheese each day. 
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Materials

QUANTITY ITEM DESCRIPTION
4.5cm x 4.5cm x 0.5cm of Swiss
4.5cm x 4.5cm x 0.5cm of cheddar
4.5cm x 4.5cm x 0.5cm of American
1 Felt tipped marker
1 Sterilized knife
12 Zip-locks
1 Grid Paper
1  rubber glove

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Procedures

1.  Take the American cheese and cut four pieces, 4.5 cm long, 4.5 cm wide, and 0.5 cm thick. 
2.  Apply the mold solution with a cotton tipped applicator across one side in both diagonals on all four pieces of cheese.
3.  Put one piece of cheese in each zip lock bag. 
4.  Label the bags by writing the type of cheese and Trial 1, Trial 2 and so on, on all of the bags 
5.  Close the Zip-locks making sure there is the least amount of air in the bag. 
6.  Repeat steps 1-6 for the Swiss and Cheddar cheeses 
7.  After you applied the mold and waited 24 hours, then place a transparent grid sheet 4.5x4.5 cm over the zip lock and color in the mold pattern. 
8.  Count the amount of squares and then you will know how much the mold has increased. 
9.  Do this for every 24 hours for one week. 
10.Record your information for Swiss, Cheddar, and American on a graphed piece of paper. 
11.Record mold growth data on every piece of cheese every day. 


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Results

The original purpose of this experiment was to discover which cheese (American, Cheddar, and Swiss) would support the most mold growth while in a room temperature cupboard. 

The results of the experiment were that Swiss grew the most amount of mold, Cheddar had the second greatest amount, and American had the least amount of mold. 

See the table and graph below: 
 

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Conclusion

My hypothesis was that American cheese will support more mold growth than the other varieties.

The results indicate that this hypothesis should be rejected because American had the least amount of mold and Swiss had the most.  Swiss was the cheese that I hypothesized that would support the least amount of mold growth because of the lack of moisture.  The reason there was virtually no mold on the American cheese was perhaps there were preservatives in the cheese.

Because of the results of this experiment, I wonder if the American cheese would support more mold than the other varieties without the preservatives.  If the cheeses would grow even more mold if I incubated them in warmer area.  If the cheese was kept in a cold climate I wonder if the mold would increase or decrease.  I wonder if I applied more mold to the cheese if it would grow a lot more mold or would it have stayed the same.

If I were to conduct this project again I would make sure that the American cheese had no preservatives.  Try to record data at the same time every day. 
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RESEARCH REPORT
 
 

INTRODUCTION

Cheese will mold when in the wrong storage place and has a lot of moisture.  This report will teach about mold and cheese.

The Growing process of Mold

 The first stage of mold are the spores. The color of mold comes from itís spores.  There are thousands of spores that can be caught in a wind current and settle to the floor, food, or your body.  Then they break open and start to produce a colony.  A colony is where many of the same organisms are growing in the same place.  Then the hyphae (hyphae are what produce after the spores break open) and spores form something called mycelium.  Mycelium is a colonial string like mass.  On top of that grows aerial hyphae or stolons.  Stolons are hyphae except they are on top of the mycelium.  The stolons are anchored by rhiziods.  Rhiziods are anchors that hold down the stolons.  Penicillum mold produces a chain of spores at the tips of the hyphae.  After the mold is done with this process the spores get caught  in any air current and land on something new and start the process over.  Some molds also have a stalk called a sporangiophore used for reproducing.  Mold can grow almost anywhere on land or sea.  Mold needs a warm dark place to grow.  If mold gets too much sunlight then the mold will not be able to reproduce.  Some molds do grow in sunlight, like the molds that kill wheat, oats, roses, and other plants. 
 
 

How Mold Eats and What it Eats

 The way mold gets nourishment is where it breaks the large molecules of what itís eating into smaller molecules so the mold can absorb it.  Mold needs food and water to grow.  There are many kinds of mold and each needs something different to grow.  Mold has no chlorophyll so it has to find itís own food.  There are two kinds of mold, thereís saprophyte and parasite .  When mold lives on non organic matter it is called a saprophyte.  When mold takes nourishment from a living thing it is called a parasite.  The most common mold is the black bread mold which lives on decaying vegetables, fruits, and bread.

The Good and Bad Things About Mold

Some of the good things about mold is it decomposes dead animals, leaves, plants, and even fallen trees.  Medicines are made from certain kinds of mold.  The bad thing is it can cause a well known disease called ringworm.  Ringworm occurs when a certain kind of mold spore falls on your body and starts to grow.  The way that ringworm is cured is by another kind of mold.  Mold can also cause athletes foot.  That happens when the spores get between your toes and starts to grow.  Mold also can spoil your food.

Fermentation

 Fermentation is a chemical process that breaks down organic matter.  This process is carried out by microbes as bacteria, molds, or yeasts.  Fermentation  is essential in production of bread, cheese,  yogurt, beer, and wines.  In some cases fermentation  can be unhealthy, like fermented milk turns sour.

Sexuality

 Molds can be asexual or sexual.  They can be sexual by one piece of mold moving into another and reproducing.  They can be asexual by one piece of mold breaking away from the whole piece and then reproducing on its own.

Cheeses

 These are the basic steps of cheese making.  First process the milk by running it through a machine that will pasteurize the milk and pump it into huge metal containers.  Next separate the curd.  Then thread the curd.  Next let the cheese ripen.  Mold is what ripens the cheese.  Finally package the cheese. You donít want any unknown mold in the package or it will spoil the cheese.  Changing this process slightly will result in many different kinds of cheese.  Cheese has lots of milks value, like proteins, minerals, and vitamins.  Cheese has milks nutrients but in concentrate form.  Here are the different textures of cheese.  Soft, Semisoft, Hard, and Veryhard.  The amount of moisture determines the classification.  More moisture the softer the cheese, less moisture the harder the cheese. American cheese has the most amount of moisture and itís the softest cheese so it will produce more mold.  Swiss is a hard cheese so it doesnít have very much moister.  With very little moisture mold doesnít grow as well.  Cheddar is also pretty hard but not as hard as the Swiss so it has a little more moisture.

Summary

 In America people love cheese and itís important to keep cheese mold-free.  Itís important because if cheese gets moldy and you eat it, it could make you sick.  Cheese manufactures use sterilized machines and air-tight packaging so the mold canít get to the cheese.  Some cheeses are ripened by special molds but you donít want unknown mold in the package.  In order to keep cheese mold free at your house put the cheese in an air tight zip-lock bag after you opened the original cheese package. 
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BIBLIOGRAPHY

Ammirati, Joe F., "Mold", World Book Encyclopedia, 1995, pp. 689-690

Ashe, Arthur J., 111, "Fermentation", World Book IBM, 1998

Carter, Joseph L., et al., Life Science, Boston, Massachusetts,  Ginn and Company, 1971

Gray, William D., What we Find When we Look at Molds, New York, Mcgraw-Hill Book Company, 1970

Marshall, Robert T., "Cheese", World Book Encyclopedia, 1995, pp. 392-394

Mitchell, Elliot, "Mold", Comptons Multimedia Encyclopedia, 1995

"Mold", The Columbia Encyclopedia, 1993 
 

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