Processed cheese, process cheese, cheese slice, prepared cheese, cheese singles or cheese food is a food product made from normal cheese and sometimes other unfermented dairy ingredients, plus emulsifiers, extra salt, food colorings, or whey. Many flavors, colors, and textures of processed cheese exist.
In the United States, the most recognizable variety of processed cheese is sold under the name American cheese, although this name also has other meanings. American cheese is processed and usually bought sliced at a grocery store. The name American cheese also has a legal definition as a type of pasteurized processed cheese under the U.S. Code of Federal Regulations.
Although processed cheese was first invented in 1911 by Walter Gerber of Thun, Switzerland, it was James L. Kraft who first applied for an American patent for his method in 1916. Kraft Foods also created the first commercially available sliced processed cheese, which was introduced in 1950. This form of sliced cheese and its derivatives have become commonplace in the United States, most notably used for cheeseburgers and grilled cheese sandwiches. The Laughing Cow is an example of European processed cheese.
Processed cheese has several technical advantages over unprocessed cheese, including extended shelf-life, resistance to separation when cooked, and uniformity of product. Its production also enjoys significant economic advantages over traditional cheesemaking processes, most often through the ability to incorporate any of a wide variety of less expensive ingredients.
The use of emulsifiers in processed cheese results in cheese that melts smoothly when cooked. With prolonged heating, unprocessed cheese will separate into a molten protein gel and liquid fat; processed cheese will not separate in this manner. The emulsifiers, typically sodium phosphate, potassium phosphate, tartrate, or citrate, reduce the tendency for tiny fat globules in the cheese to coalesce and pool on the surface of the molten cheese.
Because processed cheese does not separate when melted, it is used as an ingredient in a variety of dishes. It is a popular addition to hamburgers, as it does not run off, nor does it change in texture or taste as it is heated.
Sale and labeling 
Processed cheese is often sold in blocks, pressurized cans, or packed in individual slices, sometimes with plastic wrappers or wax paper separating them. The first commercially available individually wrapped cheese slices were introduced in the U.S. by Clearfield Cheese Co. in 1956. US Pat. 2759308 by Arnold Nawrocki was assigned to Clearfield Cheese Co. in 1956.
Legal definitions 
Due to the processing and additives, some softer varieties cannot legally be labeled as "cheese" in many countries, including the United States and United Kingdom, and so are sold as "cheese food", "cheese spread", or "cheese product", depending primarily on the amount of cheese, moisture, and milkfat present in the final product.
In the United States processed cheese is defined, categorized, and regulated by the Food & Drug Administration under the U.S. Code of Federal Regulations Title 21 (Food and Drugs), Section 133 (Cheeses and Cheese Related Products). Pasteurized process cheese can be made from a single cheese or a blend of several cheeses. Cream, milkfat, water, salt, artificial color, and spices may also be added. The mixture is heated with an emulsifier, poured into a mold, and allowed to cool. The definitions include:
- Pasteurized process cheese, which is made from one or more cheeses (excluding certain cheeses such as cream cheese and cottage cheese but including American cheese), and which may contain one or more specified "optional ingredients" (includes both dairy and nondairy items). Moisture and fat content percentage requirements vary according to standards for constituent cheeses, but in most cases fat content must be >47%.
- Pasteurized process cheese food, which is made from not less than 51% by final weight of one or more "optional cheese ingredients" (similar to the cheeses available for Pasteurized process cheese) mixed with one or more "optional dairy ingredients" (milk, whey, etc.), and which may contain one or more specified "optional ingredients" (nondairy). Moisture must be <44%, and fat content >23%.
- Pasteurized process cheese spread, which is made similarly to Pasteurized process cheese food but must be spreadable at 70° F. Moisture must be between 44% and 60%, and fat content >20%.
The US Food & Drug Administration does not maintain a standard of identity for "'Pasteurized Prepared Cheese Product'", a designation which particularly appears on many popular Kraft products (as well as some others). Neither does the FDA maintain a standard of identity for "'Pasteurized Process Cheese Product'" (emphasis on the trailing "Product"), a designation which appears particularly on many American store- and generic-branded singles. Products labeled as such may therefore use milk protein concentrate (MPC) in the formulation, an ingredient which does not appear in the above FDA definitions. The desire to use inexpensive imported milk protein concentrate is noted as motivation for the introduction of these and similar terms, and for the relabeling of some products. After an FDA Warning Letter protesting Kraft's use of MPC in late 2002, some varieties of Kraft Singles formerly labeled "Pasteurized Process Cheese Food" became "Pasteurized Prepared Cheese Product", Velveeta went from "Pasteurized Process Cheese Spread" to "Pasteurized Prepared Cheese Product", and Easy Cheese went from "Pasteurized Process Cheese Spread" to "Pasteurized Cheese Snack".
American cheese 
The best known processed cheese in the United States is marketed as American cheese by Kraft Foods, Borden, and other companies. It is orange, yellow, or white in color and mild in flavor, with a medium consistency, and melts easily. It is typically made from a blend of cheeses, most often Colby and Cheddar.
Another type of processed cheese created in the United States is Provel pasteurized processed pizza cheese, which uses Cheddar, Swiss, and provolone cheeses as flavorants. Provel cheese is commonly used in St. Louis-style pizza. Another variety of processed pizza cheeses are Mozzarella-like imitation processed cheeses, which are sometimes used in frozen pizzas.
- Under the U.S. Code of Federal Regulations Title 21 (Food and Drugs), Article 133, Section 169 (Pasteurized process cheese), the allowed usage of the term "American Cheese" for certain types of "Pasteurized process cheese" is detailed. Specifically, in paragraph (e)(2)(ii) of section 133.169, it states In case it is made of cheddar cheese, washed curd cheese, colby cheese, or granular cheese or any mixture of two or more of these, it may be designated "Pasteurized process American cheese"; or when cheddar cheese, washed curd cheese, colby cheese, granular cheese, or any mixture of two or more of these is combined with other varieties of cheese in the cheese ingredient, any of such cheeses or such mixture may be designated as "American cheese."U.S. Food and Drug Administration (April 1, 1999). "Title 21, Article 133". U.S. Government Printing Office. Retrieved 2007-02-17.
- "Emmi Gerber - Über Gerber:". Emmi Fondue AG. Retrieved 2013-03-26.
- "Kraft Foods Corporate Timeline". Kraft Foods Group, Inc. Retrieved 2013-03-26.
- Refer to U.S. Code of Federal Regulations Title 21 (Food and Drugs) Article 133 (Cheeses and Cheese Related Products) at the U.S. Government Printing Office.
- U.S. Imports of Concentrated Milk Proteins: What We Know and Don't Know?, Jesse, Marketing and Policy Briefing Paper No. 80, Department of Agricultural and Applied Economics, College of Agricultural and Life Sciences, University of Wisconsin-Madison Cooperative Extension, University of Wisconsin-Extension, February 2003. Accessed 8 February 2010.
- What is 'Real Kraft Cheese'? Chicago Business, February 5, 2007. Accessed 9 February 2010.
- WARNING LETTER CHI-6-03, U.S. Food and Drug Administration to Kraft Foods North America, Inc. 18 December 2002. Accessed 9 February 2010.
- Hulin, Belinda (2007). The Everything Pizza Cookbook: 300 Crowd-Pleasing Slices of Heaven. F+W Publications, Inc. p. 7. ISBN 1598692593. Retrieved September 30, 2012.
- Law, Barry A; Tamime, A.Y. (editors) (2010). Technology of Cheesemaking. Wiley-Blackwell. pp. (unlisted). ISBN 9781444323757. Retrieved September 30, 2012.
- American Chemical Society article on processed cheese.
- From Cheese to Cheese Food: How Kraft persuaded Americans to accept cheese by divorcing it from its microbe-laden origins.
- Calories in Cheese