What is your first reaction when you hear puffed food?

Puffed food? → shrimp fries and potato chips! → fried food! → puffed food = fried food

So in 1.0 seconds, a clear and decisive logical closed loop was formed.

In fact, it is human nature for everyone to think so, after all, in some shopping apps/applets now, the puffing column is indeed basically these, and the name of this category is "puffed potato chips", how can this not make people think crookedly? !

However, this is actually a big misunderstanding! In fact, puffed food ≠ shrimp crackers, potted potato chips, and fried food ≠!

01. What is puffing?

What does puffing mean? The volume expands and the food becomes larger.

See! These are puffed foods!

When the pressure and temperature of the food drop from very high to very low, the moisture in the food vaporizes and evaporates in an instant, the food itself is exploded (not to the extent that it will be blown up), the volume expands several times, the internal tissue forms a porous and loose structure, the original hard texture becomes crispy, and at the same time produces a unique flavor. This is puffed food. Its essence is a very small explosion that occurs inside the food. The puffed food is porous inside, which is conducive to the penetration of various digestive enzymes, so the digestibility is greatly improved.

In the 80s of the last century, we should all have seen or eaten popcorn popping on the side of the road. The oval pot containing the corn kernels is heated to a certain heat, and then the mouth of the pot is opened with lightning speed, and in the moment of "bang", the corn kernels are transformed into fragrant popcorn.

This is a typical puffing reaction, and this process has nothing to do with frying.

There are many roads to puffing, and frying is just one of them.

02. What are the means of puffing?

1. Frying and puffing

The high temperature during frying causes the moisture in the food to vaporize and evaporate, resulting in crispy puffed products, such as our common pot cakes, shrimp crackers, and potato chips.

Because of the use of oil as a medium, oil molecules migrate to the inside of food on a large scale, causing the oil content of food to soar and turn into a heat bomb. This is one of the important reasons why fried food is considered "junk food".

Take two fried potato chips on the market, one-third of them are oil, and some of them even contain nearly half of the oil.

Figure: Nutrition facts of two types of potato chips on the market

In addition to the high oil content, frying will also damage the nutrients of food.

The frying process generally lasts 180-0 seconds, and the temperature can be as high as about 0-0 °C.

At the same time, long-term high temperature and repeated frying can easily lead to changes in the quality of the oil itself, and the production of harmful substances increases, and these harmful substances may also be transferred to food with the fat, posing a threat to health. Therefore, it is better to eat less of this fried puffed food.

2. Pressing and puffing

Extrusion puffing is to do work on the extrusion of food through mechanical external force, so that the temperature of the food rises, forming a state of high temperature and high pressure, and then suddenly stop the strong external pressure, the food is instantly cooled and depressurized to the normal, free water can not withstand such a strong change, so vaporization, at the same time, the internal structure and physical and chemical properties of the food also change, forming a porous structure.

The extrusion equipment can be designed into different shapes at the outlet of the material to obtain different shapes of end products, so we can see various shapes of breakfast cereals and snack foods, strips, balls, slices, blocks, triangles, and various small animal shapes, the main one is a only you can't think of, I can't do it without me.

Extrusion is a physical process with a temperature of around 130°C that occurs almost instantaneously, so the nutrient loss is relatively small, and some are even healthier than steaming.

Macromolecules such as starch, protein, fat, and crude fiber are cut into small molecules, such as long chain starch is torn into water-soluble starch, dextrin, reducing sugar, etc., and some proteins are cleaved into peptides and amino acids.

At present, extrusion technology is being used in the development of breakfast cereals, snack cereals, infant foods, etc.

Although it is also crispy, it generally has a low oil content. You can look at this Kellogg's extruded breakfast cereal, which has an oil content of only 4.0%.

Figure: The fat content of a squeezed puffed breakfast cereal is only 4.0%

3. Hot air puffing

As the name suggests, hot air is used as a heat exchange medium to gelatinize the heated food starch, denature the protein, and vaporize the water.

Sand frying puffing is to put food materials into sand and gravel to stir-fry, and use the high temperature of sand and gravel to puff the food, which can be referred to sugar fried chestnuts.

However, sand frying has high requirements for the quality of sand, and the subsequent sand removal problem is not very easy to solve, so it is rarely used in industrial production.

4. Microwave puffing

Microwave puffing is through the radiation conduction of electromagnetic energy, the water molecules inside the food absorb the microwave and then violently shake to obtain kinetic energy, to achieve vaporization, the formation of a pressure difference between the inside and outside of the food, the vaporized water vapor moves to the outside of the food under the action of pressure, forming a porous and loose texture. Microwave puffing is mostly used in fruit and vegetable chips, cereal foods, and protein foods.

5, Compound Inflation

In order to overcome the shortcomings of a certain puffing technology, sometimes a variety of puffing technologies are combined to improve production efficiency and fully retain nutrients, such as microwave frying puffing technology.

Puffing itself is not guilty. Not all puffed foods are junk food.

The reason why people label puffed food as "high oil, high sugar, high salt, and high calorie" is that in addition to being misled by life experience, it is not excluded that some manufacturers use a lot of extra oil, salt, and sugar in order to cater to everyone's taste preferences.

Again, learn to read nutrition labels, you can identify those healthy puffed foods at a glance, some puffed grains can not only be used as snacks, but also as breakfast, as a supper is also a good choice. Therefore, improve your scientific literacy, no matter what the name or classification, you can see the essence through the phenomenon, so that you can respond to all changes with the same, so that you can pick out the product you really like from the overwhelming food shelves.