How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Abstract
Oooey gooey cheese...yum! Who doesn't like a slice of warm pizza straight from the oven?
There's nothing quite like a slice of pizza and a glass of milk, so what makes pizza so great?
The cheese! But did you know that making cheese is all about science and chemistry? In this
culinary project, you will learn more about the science of cheese making and what kind of milk
works best. Try this culinary project and you'll learn about food science and get something
yummy to eat afterward!
Objective
To investigate how different kinds of milk affect the resulting cheese.
Introduction
What makes a pizza so delicious? Is it the crust? The toppings? The sauce? A pizza just
wouldn't be a pizza without ooey, gooey, melted cheese. There is a great variety of cheeses
available. Cheese can taste buttery, bland, rich, creamy, sharp, or salty. Cheese can be hard,
like Mimolette, or soft, like Brillat Savarin. Some cheeses are so soft that you need a spoon to
eat them. Some cheeses are stinky, and some are aromatic. Whatever your taste is, there is a
cheese that can satisfy it.
Figure 1. These are examples of cheeses. (Freedigitalphotos.net, 2008.)
We don't know when humans started making cheese, but we do know that cheese making is
one of the most ancient forms of manufactured foods. There is evidence that humans in Egypt
and Europe were making cheese in 3000 BC. For ancient man, cheese was a way to preserve
and store milk. Milk spoils if it's left out too long, but some cheeses, like Mimolette, can keep
for more than a year! Since cows and sheep usually give milk in the spring and summer
months, cheese was a way for ancient humans to eat dairy in the winter months.
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Cheese making is thought to have originated in the Middle East by Arab nomads. Legend has
it that an Arab nomad stored some milk in a container made from the stomach of an animal.
As he traveled, the galloping of the horse, the hot sun, and the rennet from the stomach
served to separate the milk into curds and whey. Rennet is a natural complex of enzymes
found in mammalian stomachs that is used to digest mother's milk. Imagine the nomad's
surprise when he discovered his milk had changed to nutritious curds and refreshing whey!
Figure 2. Grated cheese, just right for pizza! (Freedigitalphotos.net,
2008.)
Milk is a biological product made up of proteins, as well as fats and other minor ingredients.
Milk proteins are 80 percent casein (pronounced "kay-sin") and 20 percent whey protein. The
casein protein is dispersed through the milk. Cheese is coagulated casein protein. Making
cheese requires an agent to collect and coagulate the casein protein. One way to collect the
casein is to acidify the milk with an acid, like lemon juice or vinegar. Once the milk has been
acidified, cheese makers use rennin, the active enzyme in rennet, to accelerate the
coagulation. Rennin causes the milk to change without changing itself; rennin is a catalyst.
To make cheese with rennet requires that the temperature of the milk be a constant
temperature. If the milk is too hot or too cold, the reaction will not take place. The kind of
milk used will also affect the end product. Sheep's milk, cow's milk, and goat's milk all result
in different cheeses. The fat content in the milk affects how the cheese feels in your mouth as
you eat it.
In this culinary project, you will make your own mozzarella cheese! It's amazing to think that
a food product we are all familiar with can have serious food chemistry behind it. Enjoy this
culinary project and be sure to share the cheese you make with friends and family!
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Figure 3. This image shows a dish made from the Indian cheese
paneer. (Feastguru.com, 2008.)
Terms, Concepts, and Questions to Start Background Research

Rennet

Curd

Whey

Enzyme

Protein

Coagulate

Acid

Catalyst
Questions

What are some different varieties of cheeses?

What are the different production methods used to make cheese? Hint: Look at one of
the bibliographical entries for the answer!

What kinds of milks are used to make cheese?
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!

What is your favorite cheese and why? What are your friends' and family members'
favorite cheeses?
Bibliography
There are many websites related to cheese making. The following is a small selection:

New England Cheesemaking Supply Company. (2008). Retrieved December 1, 2008,
from http://www.cheesemaking.com/

Wikipedia Contributors. (2008, September 5). Rennet. Wikipedia: The Free
Encyclopedia Retrieved September 23, 2008, from
http://en.wikipedia.org/w/index.php?title=Rennet&oldid=236442451
This website has good information on the varieties of cheeses and the different production
methods.

Alden, Lori. (n.d.). Cheese. The Cook's Thesaurus. Retrieved September 17, 2008,
from http://www.foodsubs.com/Cheese.html
Materials and Equipment

Stainless steel pot with a lid, 8-quart. Caution: Do not use an aluminum or an iron
pot. Making cheese requires acidifying milk, and the acid can cause the aluminum or
iron to etch, or come off of, the pot. The etched aluminum or iron would then end up
in the milk, which is not good for your health.

Stovetop

Vegetable rennet (3 tablets); available online at websites such as
www.cheesemaking.com

Cutting board

Knife, should be as long as the pot is deep

Measuring cups (2)

Spoons (2), do not use wooden spoons

Mixing bowls (2)

Food-grade citric acid, granulated form (15 teaspoons); available online at websites
such as www.cheesemaking.com

1/4 teaspoon measure

Water (11 1/4 cups), filtered non-chlorinated

Whole pasteurized milk (2 gallons)

Dairy thermometer; available online at websites such as www.cheesemaking.com (use
a sanitized internal temperature thermometer)

Slotted spoon, do not use a wooden spoon

Timer

Digital camera (optional)
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!

Cheesecloth

Colander

Microwave-safe bowl

Microwave oven

Oven mitt

Dishwashing gloves

Teaspoon measure

Salt

Bowl

Ice water

Volunteers (at least 3)

Lab notebook
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Experimental Procedure
While making cheese is definitely a science, it is considered an art as well. Sometimes your
cheese might not be perfect, but keep trying and be sure to finish all of the steps.
1. To start this science fair project, you should clean your work area. Make sure that all
of the cooking implements are clean and have no food residue on them, and that the
cheesecloth is clean and dry.
2. Place the pot on the stovetop.
3. Put one of the rennet tablets on the cutting board and cut the tablet into four equal
pieces with the knife. Dissolve one of the four pieces into 1/4 cup of filtered, nonchlorinated water. Mix well with one of the spoons. Set the mixture aside.
4. Dissolve 1 1/4 teaspoons of citric acid into 1 cup of filtered, non-chlorinated water.
Mix well with the other spoon and set the mixture aside.
5. Pour 1 gallon of whole milk into the pot. Turn the burner to the medium setting—no
higher or you might scald the milk.
6. Use the dairy thermometer to keep track of the temperature of the milk. Add the citric
acid and water mixture to the pot when the milk reaches 60°F. With the slotted spoon,
mix the citric acid mixture into the milk. Use consistent strokes. Don't mix too fast or
too slow. Mix continuously until the temperature of the milk is 90°F. Once the
temperature of the milk is 90°F, turn the burner off and take the pot off the burner.
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Figure 4. Waiting for the temperature of the milk to reach 90°F.
7. Add the rennet and water mixture to the milk. Mix the rennet mixture into the milk
using consistent strokes. Don't mix too fast or too slow. Mix the two together for 20
seconds.
8. Once the rennet has been mixed in, cover the pot with the lid and let the mixture
stand, undisturbed, for 5 minutes.
9. After 5 minutes have elapsed, uncover the pot. You should see the curds separated
from the whey. The color of the whey should be clear to light greenish yellow. The
curds should have a custard-like texture. If the whey is still milky, then let the
mixture sit for another few minutes.
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Figure 5. This picture shows the curds separated from the whey.
10. Take the knife and cut the curds into smaller pieces. Carefully insert the knife at an
angle into the curds at one end of the pot. Cut curds in an orderly fashion, from one
end of the pot to the other end of the pot, making sure to cut all the way to the
bottom of the curds and that the cuts are about 3/4 inch apart. Keep cutting until all
of the curds have been cut in one direction. Turn the pot 90 degrees and cut the curds
the same way again. You can take a photograph during this step and place it in your
lab notebook.
11. Place the pot back onto the burner. Turn the burner back onto the medium setting.
Stir the curds gently with the slotted spoon until the curds and whey are about 105°F.
Turn the burner off and take the pot off the burner.
12. Line the colander with the cheesecloth and put it in the sink. Do not turn the sink on.
Drain the curds in the colander. Gently press the curds against the side of the
colander to remove the excess whey.
13. Transfer the curds to the microwave-safe bowl.
14. Put the bowl into the microwave oven and microwave the curds for 50-60 seconds on
the "High" setting.
15. Remove the bowl from the microwave. Take care to not burn yourself. Use an oven
mitt, if necessary. How does the cheese look? Is it shiny? Is it soft? Record your
observations in your lab notebook in a data table like the one below. You can take a
photograph at this step and place the picture in your lab notebook.
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Figure 6. What your cheese may look like coming out of the microwave.
16. Put on the dishwashing gloves. The curds should now be melted into one large piece
of cheese. Gently push the cheese against the side of the bowl to remove the excess
whey. Discard the whey. Pick up the cheese and stretch it out several times. What
happens as you stretch the cheese? How long can you stretch the cheese before it
breaks? Record your observations, as well as how long you spent stretching the
cheese, in your lab notebook.
Figure 7. Stretching the cheese. This can be fun to do if you have
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
someone help you!
17. Put the cheese back into the microwave-safe bowl and into the microwave oven.
Microwave the cheese for 20-30 seconds on the "High" setting.
18. Remove the bowl from the microwave (again, using the oven mitt, if necessary) and
then drain off the excess whey by pressing the cheese against the side of the bowl
and pouring the whey out. Add 1 teaspoon of salt to the cheese and work it into the
cheese with your kitchen gloves on. Stretch out the cheese as many times as needed
until it is smooth and shiny and completely one piece. Set the cheese into a bowl of
ice water to completely cool the cheese down. The cheese is now ready to eat. Cut a
sample of cheese and taste it. Does it taste good? Record your observations in your
lab notebook.
19. Have your volunteers sample the cheese. Record their observations in your lab
notebook. Sample questions include asking them to explain how it tastes and to
describe its texture.
20. Thoroughly clean and dry all of the kitchen supplies you used, including thoroughly
rinsing out the cheesecloth and letting it dry.
Figure 8. Here is a finished ball of mozzarella cheese.
Variety of
Milk
Total Time You Spent Stretching
Each Cheese
Trial 1:
Observations
How Far Can You Stretcha the Mozzarella: The
Science of Making Cheese!
Trial 2:
Credits
Michelle Maranowski, PhD, Science Buddies
Last edit date: 2008-12-01 11:15:00
Career Focus
If you like this project, you might enjoy exploring related careers.
Food Science Technician
Good taste, texture, quality, and safety are all very
important in the food industry. Food science technicians
test and catalog the physical and chemical properties of
food to help ensure these aspects.
Bioche
Growi
chemi
Bioche
happe
substa
living
Agricultural Technician
As the world's population grows larger, it is important to
improve the quality and yield of food crops and animal
food sources. Agricultural technicians work in the
forefront of this very important research area by helping
scientists conduct novel experiments. If you would like to
combine technology with the desire to see things grow,
then read further to learn more about this exciting career.
Food S
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