Name
Date
What Makes Popcorn Pop?
By Sharon Fabian
What makes popcorn pop? Popcorn is an unusual food, but the answer
to what makes it pop is not mysterious at all. The scientific explanation
is simple, and the details might even help you decide how to pop the
best bowl of big fluffy popcorn kernels that you have ever snacked on.
Making popcorn starts with growing the right kind of corn. Popcorn is
different from the sweet corn that you eat as corn-on-the-cob. The
popcorn kernel consists of a hard outer shell with starch and water
inside. Good popping corn must have a thick rounded shell and the right
moisture content. It grows best in sunny fields. The fields must have
good drainage and be watered when they dry out. The popcorn plants
take from about ninety to about one hundred twenty days to grow. When
the kernels are hard and the husks are dry, it is time for the harvest.
Then the kernels continue to dry either on or off the cob until they reach the right moisture content, which is from
eleven to fourteen percent. Popcorn companies can easily test the moisture content by weighing the popcorn, since
popcorn with more moisture weighs more.
One feature that distinguishes popcorn from other types of corn is the outer shell. The shell of a popcorn kernel
must seal in the contents completely. It must be airtight.
The only thing that needs to be added to popcorn kernels to make them pop is heat. The heat can come from a
stove top, a popcorn popper, or a microwave. Popcorn pops the same way no matter which type of popper is used.
When popcorn kernels are heated, the water inside the kernels begins to expand. If there was an opening, the water
would escape as steam, but since the kernel is sealed tight, pressure begins to build up inside. The pressure builds
and builds. Finally, when the temperature inside the kernel reaches about four hundred fifty degrees Fahrenheit, the
shell can't withstand the pressure. It explodes. In an instant, the shell turns inside out and fluffy white popcorn
appears.
The kernel of popcorn is now forty to fifty times the size it was just seconds ago. The more the popcorn expands,
the better quality it is considered to be.
The white fluffy part comes from the starch inside the kernel. When the kernel heats up, the starch begins to turn
into a sort of gelatin. It stretches into a cluster of thin bubbles. When the kernel pops, the starch instantly turns
back into a solid, a very fluffy solid. This is similar to the way in which silly string works. It is not solid in the can
but turns solid when you spray it out.
No matter what you use to make your popcorn, it pops the same way. All you really need are popcorn kernels and
some way to heat them up really hot.
The retro-looking Jiffy Pop tinfoil domes pop this way using heat from the stove. Popcorn poppers use electricity
to heat up the kernels either plain, in an air popper, or mixed with oil. Popcorn in microwave bags pops the same
way, too. Even though microwave popcorn bags are specially designed for popcorn, you can also pop plain
popcorn in the microwave with just a brown paper lunch bag.
Add a little butter and salt if you like, and enjoy your snack!
Name
Date
What Makes Popcorn Pop?
Questions
1. It takes about ______ days for popcorn to grow.
A. two hundred
B. one hundred
C. one hundred fifty
D. ten
2. Inside a popcorn kernel, there is ______.
A. water
B. starch
C. both A and B
D. neither A nor B
3. Popcorn with a moisture content of ______ would most likely pop best.
A. seventeen percent
B. ninety percent
C. twenty percent
D. thirteen percent
4. The moisture content of popcorn can best be determined by ______.
A. measuring the circumference of a kernel
B. measuring the diameter of a kernel
C. timing how fast it pops
D. weighing it
5. The best quality popcorn ______.
A. expands the most
B. cools most quickly
C. pops fastest
D. grows fastest
6. When popcorn is heated, ______ builds up inside the kernel.
A. pressure
B. ice
C. starch
D. an electric charge
7. What do all methods of popping popcorn have in common?
Name
Date
8. How is popcorn different from other types of corn?
If you were doing an experiment to compare three kinds of popcorn, what are some of the characteristics that
you might compare? Create a chart that could be used to record the results of the experiment.
Describe another food item that is prepared in an unusual way.