The Popcorn Process
Kelley Hughes
Processing Lines 2005
Americans love popcorn. In fact, they love it so much that they consume more of it than
any other country in the world; a whopping 17.3 billion quarts of popped popcorn each year in
the US. Popcorn is America's number one snack food consumed at home, beating potato chips,
pizza, cookies and candy bars. This unique food has a long history and can be traced back 5,600
years. Ancient popcorn was discovered in the Bat Cave of West Central New Mexico in 1948
and 1950. Popcorn and other corn types had spread to all Native American tribes in North and
South America by the time Europeans began settling in the "New World.”
By then, hundreds of types of popcorn were being grown, popcorn poppers had been
invented, and popcorn was even being worn as decoration. Native Americans would bring
popcorn "snacks" to meetings with the English colonists as a token of goodwill, during peace
negotiations. It was even served at the first Thanksgiving dinner at Plymouth, Massachusetts.
Colonial housewives served popcorn with sugar and cream for breakfast and thus the first
"puffed" breakfast cereal was eaten by the settlers.
It has been grown commercially in the US since 1890. It was one of the few “treats”
people could enjoy during the great depression and was also enjoyed in mass quantities during
WWII. Popcorn sales hit a slump in the 1950s; with the increasing popularity of television,
people did not attend movies the way they once had. As people increasingly started to eat
popcorn at home, sales started to rise again. With the invention of the microwave and microwave
popcorn, sales of this fun-filled snack, in peoples’ homes, soared.
Popcorn is one of six types of corn and is the only kind that “pops.” It is known to
agronomists as zea mays everta. There are three important elements that contribute to making
popcorn “pop.” The first part is the hard shell, also known as the pericarp. The pericarp of
popcorn is very strong and retains the steam inside the corn as it is heated. Eventually the steam
builds up to the point where the kernel explodes. If the pericarp is cracked at all, the steam will
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not be able to build up, and the popcorn will
not pop. The second important element is the
moisture which is inside the pericarp. This
moisture turns to steam as the corn is heated,
without just the right amount of moisture, the
corn may not pop. The third element is
starch, which is also inside the pericarp. The
starch is what expands and forms the white,
bubbly solid that we eat.
There are two main types of popcorn: butterfly and mushroom. Butterfly is large, light
and fluffy while mushroom is small, compact, and good for coating with flavors.
Popcorn is grown mainly in the corn
belt of America which includes the states
Nebraska, Iowa, and Indiana. Popcorn is
planted between April 20th and May 10th. It
is necessary to have a soil temperature of 50
to 55 degrees Fahrenheit or 10 to 13 degrees
Celsius. Popcorn needs a very warm climate
to grow. Popcorn is harvested when it has a moisture content of 16 to 20 percent. This is very
important as moisture is one of the critical elements in popcorn “popping.” Popcorn that is too
dry may not pop and popcorn that is too wet may spoil when stored.
After the popcorn is harvested, the first step in the “popcorn process” takes place. This
step is storage or conditioning. During this step, the popcorn is conditioned until it reaches the
optimum moisture level of 13.5 to 14 percent. This step affects the seed’s coat integrity, the
appearance of the popcorn, and expansion potential. Several different methods can be used for
moisture removal. The most common are Natural Air-Drying, Natural Air-Drying with
supplemental heat, Natural Air Equilibrium Moisture Content (EMC) window, and stirring. Each
method that is used has its advantages and draw-backs, including cost and time. In industry, this
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step can be considered the most critical step so every company promotes their method of
conditioning as superior.
There are currently a number of universities in the United States researching these various
methods to determine which is superior. One of the main factors they test is expansion, which in
industry is defined as the ratio that compares the number of cubic centimeters of popped corn to
the number of grams of unpopped corn. For example, the ratio 42:1 means that for every gram of
unpopped popcorn it produces approximately 42 centimeters of popped corn.
The next major step is cleaning the popcorn. This is the point in the process when dirt,
foreign objects, and broken kernels are removed. This step is divided into three main parts:
separating by size, separating by lower and higher densities, and optical sorting. The first step of
separating by size is traditionally done by screen cleaning. Two screens, one with holes larger
then the material and one with holes smaller than the material, are used
to remove any objects with an undesirable size. The popcorn first
passes over the section with larger holes, in which the popcorn falls
through. However, larger objects do not fall through and are
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Seed cleaning
OPERATION: Seed from the teed box is distributed over the full-width adjustable-pitch
auxiliary scalper screen by a revolving feed roll.
(1) At this point the seed is subjected to an adjustable front suction. (2) which lifts out light
impurities and carries them to an air settling chamber (3). Heavier air liftings drop into the front
air liftings conveyor and are discharged to the side or fed to an optional FRC conveyor unit (4)
which discharges to the rear waste chute (10). Dust and fine impurities are discharged by the
centrally-located fan (14) to a dust collector. The aspirated seed is fed to the head of the
adjustable-pitch auxiliary scalping screen (5) Coarse impurities are tailed off and discharged from
the front of the seed cleaner. After passing through the auxiliary scalper screen, the seed flows
onto the main screen (6) which removes impurities larger than the seed and discharges them
through the side discharge trough (15). The second main screen (7) more closely sizes the seed
being processed and eliminates additional impurities through the side discharge trough. (15). The
seed flows down the seed screen (8) where dirt, sand, small weed seeds and shrunken or
immature kernels pass though to the pan and are discharged into the single point conveyor. (16)
Seed retained on the seed screen (8) is discharged into the full-width tail aspirating leg (11).
Powerful air suction again, and more selectively, removes light impurities, carrying them to the
rear settling chamber (12). Dust and chaff are drawn to the fan and discharged; heavier impurities
are discharged to the rear waste chute (10).
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subsequently removed. After the popcorn falls through, it lands on the section with smaller
holes, in which smaller items fall through, but the popcorn remains.
The next step of separating by lower/higher densities can be done with a number of
different machines, for example a gravity table and destoner can be used. A gravity table is used
to remove items less dense, such as broken, cracked, and immature kernels. It works by using
high volume fans and a perforated shaking deck. This causes the popcorn to rise and float on the
air. Depending on the popcorn’s density, the popcorn moves to different ends of the machine. In
this way, the good popcorn moves to one end and the debris moves to the other. A destoner is
used to remove items more dense, such as stones, clumps of dirt, and small pieces of metal. This
machine works the same way as the gravity table, using fans and vibrations to suspend the
popcorn; again, the good popcorn moves
to one end and the debris moves to
another.
The final part is an optical sorter
which uses high-resolution optics to
inspect kernels. This optical sorter
inspects each kernel and is able to detect
the tiniest piece of debris and even
slightly defected kernels. If any debris or
a defected kernel is found, then a quick burst of air removes the item from the machine.
At this point, the popcorn can be packaged as bulk or microwave popcorn, or it can be
popped, coated with various flavors, packaged and then sold. Bulk or microwave popcorn must
be packaged in a way such that the popcorn maintains the correct amount of moisture. Normally
in industry, bulk popcorn is packaged with plastic in the form of bags or containers. Microwave
popcorn is packed in a form of paper bag that may or may not contain flavoring or oil. Popcorn
that is popped and sold is first sent into a bulk popping machine and popped. While the popcorn
is still hot, flavor is added and the popcorn is sent through a tumbler to evenly coat the flavoring.
The popcorn is then allowed to cool, and then is packaged.
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Optical sorter
Packaging machine
Common flavors in the United States are butter, cheese, and caramel. Caramel popcorn is
particularly difficult to produce and the handling of hot caramel requires special or additional
equipment.
Caramel Popcorn Line
Popcorn can be enjoyed anytime and anywhere. Popcorn is traditionally eaten at sporting
events, carnivals, and movie theatres. It can be used as an ingredient in puddings, candy,
soups, salads and entrees.
Popcorn can be eaten with hands or with a
Popcorn Fork with a built-in salt shaker.
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