Friday, February 15, 2008

What is Cheese?

Betsy from State College, PA, sent in a question asking why certain types of cheese can be both white and yellow, so this month we will learn about cheese!

Cheese is probably in a lot of your favorite foods especially if you like pizza, lasagna, enchiladas, or macaroni and cheese. Some say that any food tastes better with cheese, but what is cheese? Cheese is essentially a preserved form of milk, which usually comes from cows but can also come from goats or sheep. About 80% of milk in its natural state is water. Cheese is basically formed when the water from milk is removed and the curds (the remaining solids) are compressed, which means the solids are squeezed or pressed together. However, cheese makers can do many different things to the curds to enhance the flavor and color to make the various kinds of cheese that you are used to. Think about how many types of cheese you already know about. It’s no wonder that cheese can be classified according to its age, country of origin, fat content, dairy content, texture, manufacturing methods, and more.

Fresh cheeses like cream cheese, ricotta, cottage cheese, and mozzarella, are the most basic cheeses because they are uncooked, unaged and sometimes still contain whey (the liquid part of milk). These cheeses must be eaten soon after they are made because they spoil quickly. Soft-ripened cheese like Brie is created from the introduction of a mold during the ripening process, or aging process. Mold is a form of fungus, which gives the cheese more flavor. Blue-veined cheeses are similar and develop blue or green streaks of harmless, flavor-producing mold throughout the interior. Washed-rind cheeses like Limburger are washed in a liquid (i.e., salted water, wine, or beer) that encourages the growth of bacteria and mold during the ripening phase, which gives the cheese a very strong smell and taste. Cheddar is an uncooked, pressed cheese, which means its curds have not been heated and the cheese has been pressed to give it a very compact, dense texture and flavor. Cooked, pressed cheese like Parmigiano-Reggiano and Provolone has its curds heated before being pressed. Processed cheese (like American, Velveeta, and spray cheese) is not technically a cheese but is actually a byproduct of the cheesemaking process. Byproducts are products made during the manufacture of something else. Processed cheese can be made with scraps of cheese but can also include whey, cream, water, dyes, gums and other ingredients. This type of cheese lasts a long time and melts easily.

So, how can some cheeses, like cheddar, be both yellow and white colors even though they are the same type of cheese? Cheese used to be different shades of white, yellow or orange, depending on when it was made during the year and also what the cows had eaten. For instance, in the spring/summer, cows eat fresh grass and other plants that contain beta-carotene and vitamin D which results in cheese that is yellow in color. In the winter, cows eat hay, which caused cheese to be pale in color. Cheese that is yellow in color is generally more desirable, so cheesemakers now dye their cheese.

Little Lion Experiment
This experiment will expose you to the many different kinds of cheese available at your grocery store or even in your own refrigerator! Much like there is a vegetable section, most supermarkets will have a section totally devoted to cheese. The next time you go to the supermarket with your parents, see if you can browse the different kinds of cheeses there. Then ask your parent if you can try 5 of these different cheeses (you will probably have to buy the cheese to taste it). Try to pick at least one kind of cheese that is two different colors (for example, yellow cheddar and white cheddar). Taste each kind of cheese and decide if you think the cheese is soft-ripened, blue-veined, washed-rind, uncooked-pressed, cooked-pressed, or processed. Try to pick cheese that you know you enjoy and also pick some cheese that you have never had. Check your refrigerator before you go to the store, too, to see what kinds of cheese you might already have! For the cheese that is two different colors, decide if you think each cheese sample tastes the same or different. Do you think one of those cheeses was dyed? Tasting the different kinds of cheese will allow you to identify the kinds of cheese that you like and dislike. You will also be able to explain to others why the cheeses can taste so different!

Science Lions is a Penn State University student volunteer organization dedicated to fostering science and engineering interest in students in kindergarten through grade 12. To learn more about the Science Lions and to submit a question for Ask Science Lions, visit