Cheesemaking

How Milk Becomes Cheese

In this lesson and lab, we will learn how cheeses from all over the world are made using the same basic processes. We will learn about:

Preserving milk
Chemistry of Coagulation
Variations in Cheese
Cheese as part of a healthy diet

The Lab: Homemade Mozzarella Cheese

Please read through the background information below before beginning the lab, which is linked at the bottom of this page. The lab instructions include a recipe link for making vegan cheese, and a cheese-tasting comparison data table for teachers who wish to offer a cheese-tasting for students before the lab, or after the lab to compare Mozzarella made by student groups.

Background Information

Early Human Question: How can we preserve milk so that we can transport it and use it before it spoils?

Early Human Answer:

Get milk from cows, goats, or sheep
(or yaks, llamas, buffalo, camels…you get the picture)
Coagulate the protein (casein) in the milk
Strain out the water
Ripen it so it keeps even longer

These four steps are the same basic process cheesemakers use today.

Coagulate: to make clump together or curdle. The change from a liquid state into a semi-solid state.

Check out A brie(f) history of cheese.

Cheesemaking Overview (also found here)

Step 1: Find a protein source, traditionally milk.

Step 2: Coagulate the milk with an acid, rennet enzyme, and/or heat.

Step 3: For all cheeses, strain the coagulated proteins (curds) from the liquid (whey).

Step 4: Ripen the cheese, using a variety of methods.

Chemistry of Coagulation

Coagulation: Making Curds and Whey

When the protein casein is in a watery environment like milk, it arranges itself into small micelles.

A micelle is a spherical form that resists interacting with water.

The micelles are soluble, which means they are dissolved in the liquid milk.

Milk also has calcium floating around.

If calcium interacts with the proteins inside the micelle, it will cause the protein to coagulate (solidify).

The outer version of casein isolates the inner proteins from the calcium.

Enter the coagulants.

These acids and enzymes react with the outer casein protein.

This causes the outer protein to lose its shape (denature) exposing the inner proteins to the calcium.

Heating the milk also causes the proteins to lose their shape and speeds up the process.

A chemical reaction takes place and the casein protein precipitates or turns into a semi-solid state.

The proteins were soluble in water when they were shaped as micelles.

When the micelle shape is destroyed, they are no longer soluble in water. They solidify into chunks and begin sticking to each other.

The insoluble proteins stick to each other, making “curds.” The surrounding liquid is the “whey.”

The fat from the milk also gets stuck in the coagulated protein.

If we stopped here and strained out all the liquid, we would have something like cottage cheese.

But most cheeses are ripened in a variety of ways that make cheddar different from mozzarella, blue cheese, parmesan, paneer, and cotija.

To ripen the cheese, cheesemakers vary the temperature, humidity, and length of time a cheese is aged.

Salting, brining, adding microbes, yeast, and even molds to the cheese gives each one a distinctive flavor and texture.

Variations in Cheese: Mozzarella

Step 1: Cow's milk for protein.
(Bufala Mozzarella is made with milk from buffalo)

Step 2: Coagulation: your recipe may call for acid, rennet, and/or heat.

Step 3: Strain the coagulated curds from the liquid whey.

Step 4: Ripen the cheese.

Not needed! Fresh chesses like mozzarella nd ricotta are ready to eat after Step 3.

Chevre (Goat Cheese)

Step 1: Goat's milk for protein.

Step 2: Coagulation: acid and/or heat.

Step 3: Strain the coagulated curds from the liquid whey.

Step 4: Ripen the cheese.

Blue Cheese

Step 1: Cow's milk for protein.

Step 2: Coagulation: Rennet and/or heat.

Step 3: Strain the coagulated curds from the liquid whey.

Step 4: Ripen the cheese.

After bacteria is added in Step 2, the cheese is ripened over time with the needed temperature and humidity.

Vegan Cheese

Step 1: Use cashews or other nuts for a protein source.

Step 2: Coagulate the protein using an acid.

Step 3: Strain the coagulated curds from the liquid whey.

Step 4: Ripen the cheese.

Cashew or other nut

Depends on the cheese. Some may be eaten as fresh cheese, some may be brined, smoked, salted or other ripening techniques.

Can cheese be part of a healthy diet?

Cheese made from milk contains all the macromolecules -- proteins, carbohydrates and fats – plus other nutrients. It is considered a whole food and generally does not contain refined sugars, white flour, and processed oils.

As metabolic diseases such as type 2 diabetes and obesity increase in the United States, people who are concerned with taking in too many calories often remove cheese from their diets. Cheese is, after all, a calorically dense food that is high in fat.

However, cheese is high in protein, releases glucose slowly over time, and contributes to a feeling of fullness. A person with diabetes can enjoy cheese in moderation without elevating their blood glucose levels.

As with most things, balance is the key. Portion size is important—a little bit of cheese goes a long way. And watch out for the processed crackers, bread, or pasta you may be eating with your cheese.

Check out this cheese comparison chart for more information.

The Lab

Making cheese? Here is a lab protocol for making Mozzarella cheese.

The lab instructions also include a recipe link for making vegan cheese, and a cheese-tasting comparison data table for teachers who wish to offer a cheese-tasting for students before the lab, or after the lab to compare student group Mozzarella successes.

Comprehension Questions:

What are four general steps to making cheese?

What is the main protein found in milk?

Describe how a change in the shape of the protein in milk changes can change properties such as solubility.

What are curds and whey?

What are some health benefits and risks of eating cheese?

What is your favorite cheese? Do some research to find out what happens at each step of the cheese-making process. You can use this slide to guide you.

Respond to the following questions if you completed the lab in class:

What are two take-aways from your cheese-making experience?

Which group's cheese did you like the most and why?

List three variables that might account for different outcomes between groups.

If you were to do the lab again, what would you do differently? Consider what you learned from your classmates' successes and/or failures.

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