I’ve always been interested in how plain old milk is turned into cheese. And I’ve wondered, what exactly is done differently to make two distinct cheeses like Mozzarella and Blue cheese?

There are several steps in the cheese-making process; what is done during each has an impact on the final taste and type of cheese. So how is cheese made you ask? Let’s break it down:

1) Raw Milk

Many animal’s milk can be used to make cheese. Buffalo, sheep, and goat’s milk are the most popular alternatives to cow’s milk.  Most cheeses can be made with milk from any animal but the final product can turn out quite differently from animal to animal. This is due to several things, including fat, protein, and lactose content.

Different types of cheese have traditionally been made with certain types of milk. Feta and Roquefort cheese, for example, are traditionally made with sheep’s milk. Chèvre is traditionally made with goat’s milk. Cheddar, Swiss, and most other common cheeses are usually made with cow’s milk.

In any case, a high quality milk is critical to make a high quality cheese. After all, it takes 10 lbs of milk to make just 1 lb of cheese!

After the milk is obtained from the desired animal based on the desired cheese, the milk is processed.

2) Milk Processing

Homogenization

Milk homogenization is the process of making milk uniform throughout. Basically, it’s a high-tech way of mixing the milk. If milk is not homogenized, a layer of cream (in cow’s milk) will rise to the top if left to sit. If you bought milk that isn’t homogenized, you would have to shake the milk every time you pour yourself a glass.

Homogenization is common practice in the commercial cheese-making industry. In artisan cheese-making however, un-homogenized milk is preferred because it allows for a slightly firmer curd. If all you have available is homogenized milk, you can correct for this by adding a small amount of calcium chloride, if desired. Some argue though, that the difference in texture is negligible in cheeses made from homogenized vs. un-homogenized milk.

In a nutshell, homogenization just ensures the milk is very well pre-mixed so the fat will not separate on its own.

Standardization

In the commercial industry, milk is also commonly standardized. This is the process of adjusting fat and protein levels to increase the final cheese yield. This is done because cows rarely produce milk with consistent levels of fat and protein throughout the year.

Standardization is also done to bring the fat and protein levels to the legal required percentages for specific types of cheese.

For example, low-fat mozzarella needs to have the fat level at a certain percentage to be labeled as low-fat mozzarella.

Three ways of adjusting fat and protein levels in the milk are as follows:

• Addition of skim milk (adding protein)
• Addition or removal of cream (adding or removing fat)
• Addition of non-fat milk solids (adding protein)
• Filtering of milk (adding or removing fat and protein)

Next, milk needs to be pasteurized to eliminate any harmful bacteria.

Pasteurization

Industrial milk pasteurizer

Pasteurization is the process off heating the milk to kill off any unwanted bacteria that may be present. Nasty bacteria like E. coli, salmonella, and listeria can sometimes be present in raw milk. To get rid of any of these bacteria, the milk is heated anywhere from 145 to 300 degrees Fahrenheit. Usually, it’s on the lower end of that range.

Some will say that pasteurization changes the flavor of milk and therefore affects the flavor of the cheese. For this reason, many artisan cheesemakers will use raw milk and forego pasteurization.

The FDA warns against the dangers of using or drinking raw milk. They claim that pasteurizing milk does not reduce the nutritional value of milk. They also warn to not eat any yogurt or soft cheeses made from unpasteurized milk.

If I’m making cheese I will play it safe and use pasteurized milk, especially since it doesn’t seem to have any major affect on the nutrition or taste of the milk and therefore final cheese product.

3) Coagulation and Curd Separation

Curds and whey

For milk to make its transformation into cheese, it needs to coagulate. This is done by acidifying the milk. When milk becomes acidic, the proteins (caseins) clump up and form curds. This can happen naturally if you let milk sit out long enough, but there are three ways to speed the process up.

Coagulation

• Heating – Milk acidifies faster if it is heated. When making cheese, the milk is first heated anywhere from 75-200 degrees Fahrenheit. It’s important that the milk be heated gradually in order to avoid scalding. After the milk reaches the desired temperature, it is usually held there for several minutes.

• Addition of Starter Cultures – Depending on the desired type of cheese, starter cultures (aka good bacteria, yeasts, or molds) are added to the heated milk. These cultures acidify the milk by fermenting the lactose (which is a kind of sugar) present in milk. The product of this fermentation is lactic acid. Starter cultures are important because they help in aging the cheese and ultimately defining the final flavor and texture. Some cheese-makers use unpasteurized milk, which can already contain the bacteria necessary to start acidifying the milk. In these cases, no starter cultures need to be added. As I noted above, though, it can be quite dangerous and risky to use unpasteurized milk. If you go this route you may just let some unwanted bacteria in with the wanted bacteria.

Milk vat where rennet and starter cultures are pre-mixed

• Addition of Rennet – Rennet is an enzyme naturally found in the lining of the stomachs of ruminants (cows, goats, sheep, etc.). Gross, I know. This enzyme is super helpful though, as it assists the starter cultures and speeds up the coagulation of milk. It does this by way of proteolysis. Nowadays, plant-based artificial rennet can be bought but traditional rennet is still widely used. Some fresh cheeses, aka un-ripened or un-aged, don’t need rennet. The starter cultures added for these cheeses are enough to coagulate the milk.

At this point, some cheeses like cheddar will have a dye added to produce that characteristic orange color.

After the milk is heated and the starter cultures and rennet are added, the solution is left for a certain amount of time. The milk should then achieve a yogurt-like consistency.

Separating the Curds and Whey

After the milk has coagulated, the solid curds will have separated themselves from the liquid whey. At this point, the whey needs to be drained off.

This is done by first cutting the solid mass of curd into smaller curds to allow more whey to be expelled. The smaller the curds are cut, the more whey will be expelled.

After the curds are cut, they are usually gently cooked in the whey to release even more whey and harden the curds a bit.

Finally, the curds are separated from the whey and left to drain in a colander or pressed into a mold, depending on the type of cheese being made.

4) Salting the Curds

Salt is such an important ingredient in cheese making. It has three major purposes. One is to add flavor. Another is to suppress bad bacteria growth.

On some cheeses, the salt suppresses bad bacteria by aiding in rind development. Salt accomplishes this by drawing moisture to the surface of the cheese, which then evaporates and leaves behind a thin layer of dehydrated, hard cheese.

The third reason salt is added is to draw out even more whey from the curds.

Salt is added at different stages in the cheese making process. Some cheeses are brined; meaning they are bathed in salt water. Some are just salted as curds. Many are salted through a combination of both techniques.

5) Pressing

Cheese cutter that cuts large blocks into smaller ones

Many fresh cheeses are essentially done after the whey is drained off and the curds are salted. This includes cheeses like ricotta, mascarpone, and queso blanco. Harder cheeses though, require pressing.

Pressing is the process of molding the cheese into the desired final shape. Usually it is either pressed into a wheel or a block.

Most of the time, pressing is accomplished by placing the curds into a mold and using a cheese press to squeeze whey out. The amount of whey that is pressed out is key in determining the final consistency of the cheese.

The cheese may also be cut into smaller blocks before it begins to be aged.

6) Aging/Curing

Aging is the last and probably most important step in developing the final flavor of the cheese. The temperature and humidity are carefully controlled during this step for a specific amount of time. The combination of these three variables allows the cheese to continue fermenting and developing flavor.

Additionally, further measures are taken on certain cheeses to encourage flavor development. Some cheeses are washed (limburger), coated (brie), or injected (blue) with certain bacteria or brines to encourage mold blooms on the rind and inside the cheese.

The aging process can take anywhere from a week to several years. The important thing to remember is that the slightest change in process can produce drastically different results. Sometimes these “mistakes” can result in new delicious variation on an old classic.

Additional Steps

Packaging cheese curds

There are pretty much endless possibilities when creating cheese and if you can think of it, it’s probably been done. There are smoked cheeses, marinated cheeses, herb and spice coated cheeses, tea-infused cheeses, the list goes on and on. These types of cheese will have special steps inserted variously in the cheese making process.

After the cheese’s flavor, texture, and appearance develops to standards, it is packaged and shipped off to stores, restaurants, and customers.

Hopefully by learning a little about the cheese making process you will try some new cheeses and maybe even make some of your own! If you do want to make your own cheeses, I highly recommend making queso blanco as your first.