Why does popcorn pop?
A bit about popcorn
Popcorn is a cereal grain, and originates from wild grass. Its
scientific name is Zea mays everta,
and it is the only type of corn to pop. Popcorn is made up of three main
components; the endosperm – the yellow/white carbohydrate made up of
soft and hard starch granules, providing energy for the germ. The germ,
which is the living part of the kernel, and the pericarp (the hull),
which is white/yellow and made of cellulose. Although, it can be red, black, or
many colours in between. (1)
Europeans discovered popcorn from Native Americans. Popcorn
used to be worn as headdresses and necklaces. It was then used as a common
breakfast, served with cream or milk. Popcorn was very common in the United
States from the late 19th century to the mid-20th century.
(2) Native American tribes flavoured popcorn with dried herbs and spices. They
also made popcorn soup and beer. (5) During World War Two, Americans ate three
times as much popcorn as they had before. (2)
Popcorn is actually good for you. It is a whole-grain, so it
provides you with fibre. It provides energy-producing complex carbohydrates. Popcorn
is naturally low in fats and calories. It is sugar free, and contains no
artificial additives or preservatives. (1)
How old is popcorn?
It is not clear exactly how old popcorn is. Archaeologists
have discovered that popcorn has been around long before Europeans arrived in
the New World. An 80,000 year old fossil corn pollen was found 200 feet below
Mexico City. Researchers discovered 1000-year-old grains of popcorn on the east
coast of Peru, so well preserved that they still popped. Popcorn has been found
in caves of Central New Mexico that, according to radio-carbon tests, is nearly
5,600 years old. (1)
Popcorn hybrids
There are around twenty-five varieties of popcorn that occur
naturally. The popcorn industries are trying to find hybrids with desirable
properties, such as ‘popability’. (6)
Why does popcorn pop?
(6)
‘Why does popcorn pop?’ is a fascinating question that I was unable to answer without research. People are fascinated by popcorn. Some Native Americans thought that a spirit lived inside each kernel of popcorn, and that when popcorn was heated, the spirit would grow angry and burst out of its home into the air as steam.
After doing some research, it seems that, although less charming, a more scientific explanation exists as to why popcorn pops. (1) Each kernel contains some water, stored inside a circle of soft starch, inside the hard outer casting. When the popcorn is heated to around 450˚F, the moisture in the kernel turns into steam, creating pressure within. As the pressure builds, the casing (the hull) bursts, and the kernel explodes, releasing the water as steam, and turning the kernel inside out. (3) The starch turns gelatinous whilst being heated, and when the hull bursts, the starch spills out and cools to around 40 times its original size. ‘All hull breaks loose.’ This creates the fluffy white popcorn.
The ideal popcorn kernel contains around 14% moisture. If it
is much drier, it will not pop, therefore, popcorn kernels should be kept in a
sealed jar to avoid the kernels drying out. (2) At harvesting, popcorn has
moisture content of 16-20%, which is too high, as the popcorn may spoil once
stored. To bring the moisture content down to 14%, the popcorn is conditioned
in giant vents, pumping warm air up through it to accelerate the drying. (4)
(1)
Click on the hyperlink to see popcorn popping in slow motion. http://www.popcorn.org/ForTeachers/TeachingGuide/PopVideos/tabid/89/Default.aspx (1)
Click on the hyperlink to see popcorn popping in slow motion. http://www.popcorn.org/ForTeachers/TeachingGuide/PopVideos/tabid/89/Default.aspx (1)
You can pop popcorn
by putting it in the microwave, heating it over a stove with some oil, or
heating it over a fire (as we did in the forest):
You can then add whatever topping you like to the popcorn and enjoy the low calorie snack!
By Lauren Watmough
