A microwave popcorn bag is an engineered, enhanced, sealed paper bag

Paper bag

A paper bag or paper sack is a preformed container made of paper, usually with an opening on one side. It can be one layer of paper or multiple layers of paper and other flexible materials. A bag is used for packaging and/or carrying items....

 in which un-popped popcorn

Popcorn

Popcorn, or popping corn, is corn which expands from the kernel and puffs up when heated. Corn is able to pop because, like sorghum, quinoa and millet, its kernels have a hard moisture-sealed hull and a dense starchy interior. This allows pressure to build inside the kernel until an explosive...

 is sold for the purpose of cooking popcorn in a microwave oven

Microwave oven

A microwave oven is a kitchen appliance that heats food by dielectric heating, using microwave radiation to heat polarized molecules within the food...

. These bags and their contents are sometimes referred to as microwave popcorn. In addition to the dried corn the bags typically contain solidified oil

Cooking oil

Cooking oil is purified fat of plant origin, which is usually liquid at room temperature ....

, one or more seasoning

Seasoning

Seasoning is the process of imparting flavor to, or improving the flavor of, food.- General meaning :Seasonings include herbs and spices, which are themselves frequently referred to as "seasonings"...

s (often salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

), and/or natural or artificial flavorings.

A popcorn bag may also refer to the sorts of decorated paper bags that fresh popped popcorn is sometimes sold in.

Design

The bag is typically partially folded when it is placed in a microwave, and inflates as a result of steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 pressure

Pressure

Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 from the heated kernels.

The design of a microwave popcorn bag is specifically keyed to avoid popped kernel scorching, an undesirable effect that takes place when popped kernels are heated above 300 °F (148.9 °C).

A susceptor

Susceptor

A susceptor is a material used for its ability to absorb electromagnetic energy and convert it to heat . This energy is typically radiofrequency or microwave radiation used in industrial heating processes, and also occasionally in microwave cooking...

, usually a metallised film

Metallised film

Metallised films are polymer films coated with a thin layer of metal, usually aluminium. They offer the glossy metallic appearance of an aluminium foil at a reduced weight and cost...

 laminated onto the paper of the bag, absorbs microwave

Microwave

Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...

s and concentrates heat at the film interface, thus ensuring a heat distribution focused on the hard-to-heat flavor coating so that the unpopped kernels are evenly coated prior to popping, thereby ensuring even flavor throughout the product.

An early susceptor popcorn bag design was patented by the American company General Mills

General Mills

General Mills, Inc. is an American Fortune 500 corporation, primarily concerned with food products, which is headquartered in Golden Valley, Minnesota, a suburb of Minneapolis. The company markets many well-known brands, such as Betty Crocker, Yoplait, Colombo, Totinos, Jeno's, Pillsbury, Green...

 in 1981 (US Patent #4,267,420).

Safety issues

Care in package design is needed for food safety

Food safety

Food safety is a scientific discipline describing handling, preparation, and storage of food in ways that prevent foodborne illness. This includes a number of routines that should be followed to avoid potentially severe health hazards....

.

One danger of the microwave popcorn bag is that after one use the susceptor typically "will lose its ability to safely react to microwave energy. If it is reheated, the changes in the susceptor can cause it to burn.

In 2006, concerns were raised about the levels of perfluorooctanoic acid

Perfluorooctanoic acid

Perfluorooctanoic acid , also known as C8 and perfluorooctanoate, is a synthetic, stable perfluorinated carboxylic acid and fluorosurfactant. One industrial application is as a surfactant in the emulsion polymerization of fluoropolymers. It has been used in the manufacture of such prominent...

 (PFOA, a chemical related to Teflon) in popcorn bags. When opening the popcorn bag directly to the face, it is possible to uptake harmful levels over time. The high temperatures used in popping popcorn may facilitate the transfer of the chemical, which is carcinogen

Carcinogen

A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

ic in lab animals, into the popcorn oil. DuPont

DuPont

E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...

 has agreed to eliminate almost all use of the chemical by 2015.

Home-made alternatives

Concerned with the above issues people have been making their own popcorn bags from simple paper bags, or popping the popcorn in the microwave in other containers including large glass bowls with heavy, but not airtight glass lids. Both of these home made approaches remove the threat of exposure to artificial flavoring and PFOA, but have a chance of leaving some corn kernels unpopped due to randomness of the microwave radiation distribution in a microwave. However, it is possible to cook the unpopped kernels a second time.

See also

• Kettle corn
  Kettle corn
  Kettle corn is a sweet-and-salty variety of popcorn that is mixed or seasoned with typically, a light colored refined sugar, salt, and oil. It was traditionally made in cast iron kettles, but may also be made in metal pans now.-History in the United States:...
  
   the sweet popcorn that is also sold in microwave versions
• Popcorn maker
  Popcorn maker
  A popcorn maker is a device used to pop popcorn. Commercial popcorn machines are usually found in movie theaters and carnivals, producing popcorn of the oil-popped type, which has approximately 45% of its calories derived from fat...