Popcorn is one of the traditional snacks in our country. In the streets and alleys that many post-80s remember, hawkers make popcorn with hand-cranked popcorn machines. The structure of the popcorn machine is also relatively simple. The main part is an oval black iron stove with an opening at one end. Put an appropriate amount of corn kernels or rice into the furnace, close the furnace cover at the opening, and heat the iron furnace on the fire. There is a barometer on the furnace cover, which can display the pressure value in the furnace in real time. When the air pressure rises to a certain level, put the open end of the furnace into the bag, open the furnace cover, and with a loud bang, a large amount of popcorn grains are sprayed into the bag from the furnace, and the popcorn is made.

Why does corn puff up into popcorn?

The expansion of corn into popcorn is actually a combination of temperature and pressure. In a sealed container with a constant amount of air inside, as the temperature increases, the pressure inside the container increases. The same is true for the iron stove of the popcorn machine. When the iron stove is heated, the pressure of the air sealed in the stove gradually increases; at the same time, the rice in the stove is also subjected to high temperature, and the moisture inside the rice is gradually evaporated and released. accumulate in the furnace. As the temperature continues to rise, the pressure in the furnace is also increasing. Under the action of high air pressure, the evaporation of water in the rice is hindered, and the remaining water in the rice is also in a state of increasing temperature and pressure, making the rice grains like a balloon full of air. Because it is also restricted by the air pressure in the furnace, the air pressure difference is not large enough, so the rice grains have not burst open for the time being. After the air pressure in the furnace rises to 2-3 atmospheres, the heating is stopped. At the moment when the furnace cover is opened, the rice grains in a state of high temperature and high pressure suddenly come into contact with the environment with low air pressure, breaking away from the binding force of the air pressure in the furnace, the moisture in the rice grains expands rapidly, forming popcorn.

Nowadays, the old-fashioned popcorn machine is basically replaced by the new commercial movie theater popcorn machine. The principle is basically the same in essence, but the equipment of the new process is more advanced, safer, and the production efficiency is higher. It can also make various flavors. The taste is also richer.

Popcorn tastes crisp and fragrant, but it is not suitable to eat too much. There is a layer of lead or lead-tin alloy in the furnace and opening of the old-fashioned popcorn machine. During the high temperature process, lead will be released in the form of lead smoke or lead vapor, which is easily absorbed by loose popcorn. Eating too much popcorn with high lead content is harmful to the body, especially after the lead is absorbed by the body, it will cause harm to the nerves, hematopoietic system and digestive system, making children's growth retardation and weak resistance, the main symptom is irritability Restlessness, loss of appetite, diarrhea, or constipation. Now commercial movie theater popcorn machines in movie theaters all use electrical appliances to bake popcorn, but some popcorn contains too much additives such as margarine and essence, which increases the energy and trans fatty acid content of popcorn, so people eat it in large quantities for a long time It is also unhealthy.

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