Do you know that?/You know what? Do you know that?/You know what? There was popcorn in the Song Dynasty. What did the ancients do with it?

There are actually three kinds of popcorn in our life. But the principle is the same, let the water vapor or air inside the ingredients expand, thus making the ingredients fluffy. This process is called puffing.

The first is the simplest, that is, atmospheric heating (frying), that is, western-style popcorn. This method mainly depends on the vaporization of water, which requires the skin of the food to be dense and airtight, otherwise the water vapor inside will be directly lost and the food will not expand. If rice does this, it can only be fried rice instead of popcorn. Among the common ingredients, corn is the most convenient to obtain, which is one of the reasons why western-style popcorn mainly chooses corn. In fact, rice (rice with skin), peas, broad beans and so on. Anyone can do this, but few people in the city see it.

The second is called airflow expansion. This method is to heat granular food in a pressure-resistant container. When the internal temperature and pressure are high enough, the pressure suddenly decreases, and the food that has been partially gelatinized at high temperature expands rapidly because of the internal water vapor and the infiltrated high-pressure air. Friends born in the 1980s should be deeply impressed by this kind of thing. It is called a manual air expander, which was invented by the Japanese and looks like a bomb. The owner of popcorn bows left and right, shakes the bellows and shells, and looks at the barometer on the shells from time to time. Under certain pressure, the master picked up the shell and stuffed it into his pocket, revealing only a steel bar. He was not afraid of the heat, so he knocked it out/kicked it out/pulled it out by hand. With a bang, white smoke rose, and then the children around them covered their ears and grinned at the other end of their pockets. This is a unique childhood joy in the 1980 s, and it is becoming more and more rare now.

Because there are already high-pressure containers, all cracked solid components can explode, not just crops with hard skins. Rice, wheat, soybeans, corn, and even rice cakes and gluten can be used.

In addition to the manual blower, there is also an industrial air expander, which looks like a cannon. Granular commercial puffed food, such as popcorn, basically comes out of the air expander.

The third type is called extrusion expansion, and the specific implementation method is also called screw expander. That is the protagonist of Zhihu's classic question "Why can diesel engines make popcorn". .

It cuts up raw materials, and extrudes them through intermeshing screws, or screws and inner screw sleeves, so as to realize the high pressure and high temperature of starch paste, and at the same time, it is transported outward with the rotation of threads. When the raw material paste emerges from the molding opening, the pressure suddenly decreases, so the water evaporates and expands. Compared with the airflow expander, the extrusion expander has an extra step of chopping raw materials, so it can not only use raw grain, but also use scraps such as powder, and the produced food can be in various shapes.

Our common puffed biscuits, such as snow cakes and scallops, are all made by large extrusion extruder.