Cheese is a relatively simple product. It is made with milk, enzymes - proteins that can break down other proteins - bacterial cultures and salt. There are many complex chemical processes involved in cheese making that determine whether the cheese is soft and delicate like mozzarella or hard and flavorful like parmesan.
In fact, people have been making cheese for about 10,000 years. Roman soldiers received cheese as part of their rations. It is a nutritious product containing protein, calcium and other minerals. Because of its long shelf life, it can be transported, traded and shipped long distances.
"In the United States, cheese is mostly made from cow's milk. But you can also find cheese made from the milk of other animals-sheep, goats, and even water buffalo and yaks," says John A. Lucey, a professor in the Department of Food Science at the University of Wisconsin-Madison, a food scientist who has studied cheese chemistry for the past 35 years.
Unlike yogurt, another fermented dairy product, when making cheese, cheesemakers remove the whey, which is water. Milk is made up of about 90% water, while cheese like cheddar is made up of less than 38% water.
Removing water from milk to make cheese results in a firmer, firmer product with a longer shelf life because milk is a very unstable product and spoils quickly. Before the invention of refrigerators, milk would sour quickly. Making cheese was a way to preserve the nutrients in milk so that you could eat it after a few weeks or months.
How cheese is made
All cheesemakers (or cheese makers) first pour the milk into a cheese vat and add a special enzyme called rennet. This enzyme destabilizes the proteins in the milk, after which the proteins join together to form a gel. Essentially, the cheesemaker turns the milk from a liquid into a gel.
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After 10 minutes to an hour, depending on the type of cheese, the cheesemaker cuts this gel, usually into cubes. Cutting the gel helps some of the whey, or water, separate from the curd, which is made up of milk and is similar to a yogurt gel. When the gel is cut into cubes, some of the water leaves the newly cut surfaces through small pores, or holes, in the gel.
The goal of the cheesemaker is to remove as much whey and moisture from the curd as needed for a particular recipe, and this is accomplished by stirring or heating the curd, which helps release the whey and moisture.
Depending on the type of cheese, the cheesemaker drains the whey and water from the vat, leaving the curd. For harder cheeses, such as cheddar, the cheesemaker adds salt directly to the curd while it is still in the vat. Salting removes more whey and moisture from the curd. The cheesemaker then packs the curd into molds or hoops - which are containers that help form the curd into a block or wheel and hold it there - and places them under pressure. The pressure compresses the curd in these hoops and it binds together to form a solid block of cheese.
Cheesemakers salt other cheeses, such as mozzarella, by placing them in a salt solution called brine. The block or wheel of cheese floats in the brine for hours, days, or even weeks. During this time, the cheese absorbs some of the salt, which gives it flavor and protects it from unwanted bacteria and pathogens.
Cheese is a living, fermented product
While the cheesemaker is doing all these things, several important bacterial processes take place. At the very beginning of the process, the cheesemaker adds cheese cultures - bacteria that he chooses to give certain flavors. By adding them to the milk while it is still liquid, the bacteria have time to ferment the lactose it contains.
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Historically, cheesemakers used raw milk and the bacteria in raw milk caused the cheese to sour. Now, cheesemakers use pasteurization, a mild heat treatment that destroys all pathogens present in raw milk. But with this treatment, cheesemakers have to add bacteria called sourdough starter to "kick-start" the fermentation process.
Pasteurization provides a more controlled process for the cheesemaker because he or she can select specific bacteria to add rather than those present in the raw milk.
Essentially, these bacteria eat (ferment) the sugar - lactose - and in doing so produce lactic acid, as well as other desirable flavor compounds in cheese, such as diacetyl, which smells like hot buttered popcorn.
In some cheeses, these cultures remain active in the cheese long after it leaves the cheese vat. Many cheesemakers age their cheeses for weeks, months or even years to give the fermentation process more time to develop the desired flavors. Aged cheeses include parmesan, aged cheddar, and gouda.
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Essentially, cheesemaking is the process of concentrating milk. Cheesemakers want the final product to contain milk proteins, fats, and nutrients without a lot of water. For example, the main milk protein that is captured during the cheese making process is casein. Milk may contain about 2.5% casein, but a finished cheese, such as cheddar, may contain about 25% casein (protein). Thus, cheese contains many nutrients, including protein, calcium, and fat.
The limitless possibilities of cheese
There are hundreds of different varieties of cheese made from cow's milk, and the production of all of them starts with milk. All of these varieties are obtained by modifying the cheese-making process.
For some cheeses, such as Limburger, the cheesemaker rubs a salve, a solution containing different types of bacteria, on the surface of the cheese during the aging process. For others, such as Camembert, the cheesemaker places the cheese in certain conditions (such as a cave) that promote mold growth.
Other cheeses, such as cheddar, are bandaged or covered with ash. Adding bandages or ashes to the surface of the cheese helps protect it from excessive mold growth and reduces the amount of moisture lost to evaporation. The result is a firmer cheese with a strong flavor. Over the past 60 years, cheesemakers have learned how to select the right bacterial cultures to produce cheese with a specific flavor and texture. The possibilities are endless and there is no limit to the cheesemaker's imagination.