بخش سوم

Page 88

Track 29

Listening 3

Cheese is one of the world’s oldest foods.

It was made by the ancient Egyptians over 3,000 years ago.

It is a valuable food, since it contains vitamins and protein.

It is used both as a food itself and in many different types of cooking.

There are hundreds of different types of cheese around the world, but they are almost always made from the same thing: milk.

Cheese is made from several different kinds of milk, including cow’s, sheep’s, and goat’s milk.

Most cheese in the United States is made from cow’s milk.

Cheese also contains water. A soft cheese, like Brie, contains more water than a hard cheese, like Parmesan.

Cheese is produced through a process called “fermentation.”

The process of making cheese was probably discovered by chance.

Ancient people used to make bags using the skin from an animal’s stomach.

When they used these skin bags to carry milk.

bacteria from the animal’s skin reacted with the milk to begin the fermentation.

The result was cheese.

Today, cheese making is a very scientific process.

First, the milk that will be used is pasteurized, which means that it is heated to remove all bacteria.

Then, specially cultivated bacteria, called “cultures,” are added to the milk.

The milk is kept fairly warm during this period to help the cultures grow.

As they grow, the bacteria cultures sometimes release bubbles of carbon dioxide.

These bubbles help make the holes in Swiss cheese.

Next, as the milk ripens, it forms a solid substance.

This substance is called “curd.”

The curd is removed, and the water is drained from it.

The curd forms the basis of the cheese and may be treated in different ways.

Finally, once it is matured and dried, the cheese is ready to eat.