The Science of Popcorn
Popcorn is one of the great scientific breakthroughs of our times. Forget the theory of relativity. The discovery that an apparently inert hard piece of plant matter can miraculously transform itself into a delicious healthy popcorn snack is a better contribution to human existence than any explanation of gravity or electro magnetism. Popcorn is a type of corn (Maize). When it’s heated correctly it expands from its kernel and puffs up. Popcorn can ‘pop’ because the kernels have a hard shell sealed with moisture which encases a dense starchy core. The kernel is heated, pressure builds up inside, and eventually a small explosion ensues. Some types of corn are specially cultivated to make good popcorn. But how do we make good popcorn? To do so it helps to understand the science.
History and Health
Popcorn was discovered by the inhabitants of what is now Peru. Evidence of popcorn related activity goes back nearly 7000 years. So the Peruvians were popping corn .long before the Egyptians built the pyramids or had even started organising into a proper civilisation. Legends that English settlers discovered the American Indians making popcorn in North America are however wrong. There’s not even any reliable evidence that the American Indians grew any suitable corn. During the Great Depression however popcorn thrived in America owing to it being so cheap. And during World War Two when sugar was rationed Americans compensated by eating three times as much popcorn. Today Indiana and Nebraska lead the way in production of the varieties of maize specifically grown for popcornbut Texas is making its own bid for leadership In a future life when the oil will have run out and assuming Miss Ellie’s beloved ‘Southfork’ ranch hasn’t been ‘fracked’ to destruction, JR Ewing may be aspire to be the top ‘popcorn baron’. In the meantime popcorn is the ‘official state snack food’ of Illinois.
Popcorn is a controversial topic in the ‘health and safety’ community. It’s generally considered to be a health food but some caution against excessive (or even any) popcorn consumption. The American Academy of Pediatrics states that popcorn should not be given to small children in case they choke. And the artificial butter flavorant (diacetyl) used in microwave popcorn is alleged to cause respiratory illness. Nevertheless air popcorn is high in anti-oxidents and dietary fibre and is free from sugar and salt. Popcorn mostly consists of air so is also low in calories. The negative health effects however arise from the things we add to it (mostly fat, salt or sugar). In the 1990s American Cinema Popcorn was found to have more fat in it than a full breakfast, a Big Mac and
Fries, and a steak dinner combined. A small popcorn from one American cinema group contains the equivalent of a day and a half recommended fat intake. Add to that the obligatory half gallon of (non ‘diet’) cola, battleship sized ‘Hot Dog’, and 20 ounce chocolate bar that usually come with it, it’s not surprising that so many American Cinema goers are ‘big boned.
A Scientific Explanation for Popcorn
As heat is applied the water and the oil around it the corn kernel, gets hot. But the kernel has a moisture proof hull which acts as a sealed pressure cooker. Eventually the moisture in the kernel turns into superheated pressurised steam causing the starch inside the kernel to gelatinize. This makes it pliable and soft. Throughout the process the pressure continues to rise until it becomes too much for the hull. At a pressure of about 130-140 psi, (depending on altitude), and at a temperature of about 180 degrees (nearly twice the boiling point of water) the hull fractures. This causes a sudden drop in pressure inside the kernel causing the steam to expand. The starch and proteins in the endosperm in the corn expand into aerated foam and foam cools into popcorn. Most types of maize will produce popcorn but the best ones are those cultivated for the purpose. ‘Zea mays everta’, a kind of flint corn, appears to be the favoured variety.
Small amounts or popcorn can be made in the home but commercial volumes only became possible with the advent of Charles Cretors’ popcorn machine in
Chicago in 1885. Charles exhibited his breakthrough at the Columbian Exposition in 1893. But rivalry broke out there and then. F W Rueckheim offered fairgoers his own rival Candied Popcorn (popped corn flavoured with molasses whilst in 1896, after only three more years of intensive research his brother Louis Rueckheim came up with a slightly different version and called it Cracker Jack Popcorn. It is not clear how these popcorn products differed from one another save for the flavours applied. Charles Cretors’ invention became the first patented steam driven popcorn machine to pop the corn in oil. Before that popcorn vendors made their popcorn in a wire basket over an open flame. This predictably resulted in some hot dry unevenly cooked treats or sometimes just a pile of cinders. Charles Cretors’ machine used a mixture of one third clarified butter and two thirds lard with some salt added. The mix was capable of surviving the temperatures of more than 230 degrees centigrade required to reach critical popcorn making conditions without engulfing the popcorn technicians in smoke or the popcorn catching fire. Charles Cretors’ machine had a further decisive advantage. The steam engine and gears which operated the popcorn stirring shaft also powered an amusing robotic clown called the ‘Toasty Roasty Man’. The steam powered clown could be relied upon to amuse popcorn enthusiasts of all ages whilst they waited for their corm to pop. KCS Advice Sustainability Section thoroughly approves of the way in which the popcorn machine made use of its waste energy. Not only did the waste heat give life to the highly amusing clown, but the exhaust from the steam engine was further used to keep the popcorn warm in its pan, and even to operate the whistle to tell popcorn lovers when the corn was ready. The device was an ecological miracle. It turned the waste heat into laughter, ambient warmth, and mobile communications. There are however reports of some smaller children being frightened by the clown and some older popcorn lovers finding the clown’s appearance ‘sinister’. A man who had been entertaining himself in a nearby bar for several hours, is reported to have mistaken the clown for the popcorn seller, and complained that it was variously ‘ignoring’ him and giving him ‘funny looks’.
Households can now buy machines which make small amounts of popcorn (typically up to eight pints, which by American standards is a ‘snack’). Some domestic popcorn machines have ‘air poppers’ which work by keeping the popcorn from burning and which blow the popcorn out through a chute. The majority of corn intended for home popping is nowadays packaged for use in a microwave oven
The Chinese have their own popcorn making process. Chinese corn poppers stand in the street with devices called ‘popcorn hammers’ consisting of a cast iron canister with a heavy sealable lid. The popcorn maize in placed in the canister and the lid is then sealed. The canister rotates on a fire like a rotisserie chicken. When the pressure gauge on the canister reaches the correct level it’s removed from the fire, put in a canvass sack and the lid released. A large explosion ensues and the popcorn fills the sack. The method is thought to have first been used for puffing rice and probably started in the ‘Song Dynasty’ which replaced the ‘Five Dynasties and Ten Kingdoms period’ in 960. Marco Polo may been there when the technology was in its infancy. The popcorn hammer even survived Chairman Mao’s cultural revolution.