Popcorn pops because each kernel contains water and starch enclosed in a hard shell. When the kernel is heated, the water turns into steam, creating internal pressure until the shell breaks, causing the kernel to pop and transforming the starch into a white, fluffy foam.
Popcorn kernels are primarily composed of three parts: a very hard outer shell called the pericarp, a starchy internal tissue known as endosperm, and a small embryo referred to as the germ. The pericarp acts as a shell: very rigid, it traps moisture under pressure, which is around 13 to 15% in a healthy kernel. Inside, the endosperm mainly stores starch in the form of small compact granules, which play a key role in popping. The germ, on the other hand, is the small nutritional part: it contains some lipids and proteins. This specific combination – rigid shell, compact starch, and ideal moisture – means not all corn can pop; only certain specific types have the perfect recipe.
For a kernel of corn to pop, it is essential that it contains just the right amount of water inside. Generally, this is around 13 to 14% moisture. When you heat the kernel, this internal water quickly turns into steam. It takes up much more space than liquid water: the volume of this steam can reach up to about 1700 times that of the initial water! Obviously, all this steam is trying to escape, but it is trapped in a tough, airtight shell. As a result, the internal pressure rises rapidly until the shell eventually bursts, suddenly releasing this accumulated steam, causing the explosion you hear as a "pop." Without this precise little bit of humidity measured inside the kernel, there is no steam, no pressure, and therefore no popcorn.
The outer shell of the corn kernel, also known as the pericarp, plays a crucial role in transforming the kernel into popcorn. It is particularly hard, impermeable, and resistant, which allows it to retain the pressure generated inside when heated. As the temperature rises, the water contained in the kernel gradually turns into steam, but the shell holds on and keeps this trapped steam inside. Consequently, the pressure inside the kernel increases significantly until the resistance of the pericarp is exceeded. It suddenly bursts, releasing the interior of the kernel, which expands rapidly and creates that famous pop. Ultimately, it is the strength and impermeability of this shell that determine whether your corn will pop perfectly or just sadly open without producing a quality popcorn.
When the corn kernel heats up, the moisture inside it quickly turns into steam. The hotter it gets, the more this steam expands and pushes against the tough shell of the corn. As a result, the internal pressure rises, becoming enormous, about ten times the atmospheric pressure. The kernel holds on for a while thanks to its hard shell, but once it reaches a certain limit, it's too much. Boom! The kernel violently bursts due to this accumulated pressure, instantly transforming the inside into a light foam. What we call popcorn is simply that: the inside of the corn kernel in the form of expanded starch, set in motion by the explosion.
When you heat your corn kernel, the water inside turns into steam, and its pressure increases rapidly. The shell, super strong until then, can no longer hold up when the pressure becomes too high. It bursts all of a sudden! As a result, the starch contained in the kernel, which was previously compact, relaxes and quickly expands, creating that funny light white foam we call popcorn. This super fast change is what we call a physical transformation, because everything bursts, but nothing disappears or appears: the kernel simply changes state and shape due to heat and the accumulated internal pressure.
The ideal temperature for achieving optimal and consistent popping of popcorn kernels is generally around 180°C to 200°C.
The characteristic 'pop' you hear when cooking popcorn is due to the sudden release of steam when the kernel's shell cracks under pressure.
Not all corn kernels can pop! Only certain specific varieties of corn, such as 'Zea mays everta', have the suitable characteristics that allow them to produce popcorn.
A popcorn kernel can reach an internal pressure of about 9 bars before it bursts, which is higher than the pressure of a standard car tire!
To effectively preserve your popcorn and ensure a good internal moisture level, store it in an airtight container placed in a cool, dry, and dark location. This way, you will maintain its optimal popping properties for much longer.
Yes, popcorn does not necessarily require oil to pop. Oil is simply used to enhance the heating and add a slight flavor. You can pop popcorn using just hot air (with an air popper) or in the microwave in a suitable container.
Generally, a temperature between 180°C and 200°C is optimal for effectively popping popcorn. This temperature range allows for quick and even heating of the kernels, making it easier for them to pop without the risk of burning.
Some grains may have a cracked shell or insufficient moisture content, preventing the internal pressure from rising properly. These grains, commonly referred to as "recalcitrant grains," will generally remain unpopped at the bottom of the container.
No, only specific corn kernels, known as popcorn, have the proper structure and moisture content to pop under heat. Traditional corn varieties do not contain the necessary internal moisture or the essential tough shell to produce popcorn.
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