Puffed food = fried food? This is a big mistake

What is your first reaction when you hear puffed food?

Puffed food? → Prawns, rice crackers and potato chips! → Fried food! → Puffed food = fried food

Thus, within 0.1 seconds, a clear and decisive logical loop was formed.

In fact, it is natural for people to think this way. After all, in some shopping apps/applets nowadays, the puffed potato chips section is basically filled with these products, and the name of this category is "puffed potato chips". How can people not think of something wrong? !

However, this is actually a huge misunderstanding! The shopping software is divided in this way just for convenience. In fact, puffed food ≠ shrimp chips, rice crackers, and even less ≠ fried food!

01

What is puffing?

What does puffing mean? The food expands in volume.

Look! These are all puffed foods!

Figure: Reference 1

When the pressure and temperature of food drop from very high to very low, the water in the food vaporizes and evaporates in an instant, the food itself is blown up (not to the point of being blown up), the volume expands several times, the internal tissue forms a porous loose structure, the original hard texture becomes crispy, and a unique flavor is produced. This is puffed food. Its essence is a very small explosion inside the food. After puffing, the food is porous inside, which is conducive to the penetration of various digestive enzymes, so the digestibility is greatly improved.

In the 1980s, we all probably saw or ate popcorn that was freshly popped on the roadside. The oval pot filled with corn kernels was heated to a certain temperature, and then the pot was opened at lightning speed. At the moment of the "pop", the corn kernels immediately turned into fragrant popcorn.

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

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

02

What are the methods of puffing?

1. Frying and puffing

The high temperature during frying causes the moisture in the food to vaporize and evaporate, forming crispy puffed products, such as the common rice crust, shrimp strips, and potato chips.

Because oil is used as a medium, oil molecules migrate into the food on a large scale, causing the oil content of the food to soar, turning it into a calorie bomb. This is one of the important reasons why fried food is regarded as "junk food".

Take any two types of fried potato chips on the market, one-third of them are oil, and some even have an oil content of nearly half.

Figure: Nutritional composition of two types of potato chips sold on the market

In addition to the high oil content, frying will also cause certain damage to the nutritional components of food.

The frying process generally lasts 20-30 seconds, and the temperature can be as high as around 160-180°C. The proteins, vitamins and other nutrients in the food components are denatured due to the high temperature and lose their original functions, which reduces the nutritional value of the food itself.

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

2. Extrusion

Extrusion puffing is the process of squeezing food through external mechanical force, which causes the temperature of the food to rise, forming a state of high temperature and high pressure. The external strong pressure is then suddenly stopped, and the food is instantly cooled and reduced in pressure to normal. The free water cannot withstand such a drastic change and thus vaporizes. At the same time, the internal structure and physical and chemical properties of the food also change accordingly, forming a porous structure.

The extrusion and puffing equipment can be designed into different shapes at the material outlet to obtain final products of different shapes. Therefore, we can see breakfast cereals and snack foods in various shapes, such as strips, balls, slices, blocks, triangles, and various small animal shapes. The main feature is that there is nothing I can't do, as long as you can think of it.

Extrusion puffing is a physical process with a temperature of about 130°C and happens almost in an instant, so the nutritional loss is relatively small, and some are even healthier than steaming.

Large molecules such as starch, protein, fat, and crude fiber are cut into small molecules. For example, long-chain starch is torn into water-soluble starch, dextrin, reducing sugar, etc., and some proteins are broken down into peptides and amino acids. The originally rough food becomes delicious, easy to digest and absorb, and easier to prepare and eat.

Currently, extrusion puffing technology is being used to develop breakfast cereal foods, snack cereal foods, infant foods, etc. using coarse grains as raw materials.

Although it also has a crispy texture, its oil content is generally lower. For example, this Kellogg's extruded breakfast cereal has an oil content of only 1.4%.

Figure: The fat content of an extruded breakfast cereal is only 1.4%

3. Hot air expansion

As the name suggests, hot air is used as a heat exchange medium to gelatinize the starch, denature the protein, and vaporize the water in the heated food. Generally, there are air puffing, baking puffing, and sand frying puffing.

Sand frying and puffing is to fry food materials in sand and gravel, and use the high temperature created by the sand and gravel to puff the food. For details, you can refer to sugar-fried chestnuts.

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

4. Microwave puffing

Microwave puffing is a process of electromagnetic energy radiation conduction. After absorbing microwaves, water molecules inside the food vibrate violently to gain kinetic energy, and then vaporize. This creates a pressure difference inside and outside the food. The vaporized water vapor moves to the outside of the food under pressure, forming a porous and loose texture. Microwave puffing is mostly used for fruit and vegetable chips, cereal foods, and protein foods.

5. Compound expansion

In order to overcome the shortcomings of a certain puffing technology, multiple puffing technologies are sometimes used in combination, which not only improves production efficiency but also fully retains nutrients, such as microwave frying puffing technology.

Puffing itself is not a sin, and not all puffed foods are junk food.

The reason why people label puffed foods as "high in oil, high in sugar, high in salt, and high in calories" is not only because they are misled by life experience, but also because some manufacturers use a lot of extra oil, salt, and sugar in order to cater to everyone's taste preferences.

Again, if you learn to read nutrition labels, you can identify healthy puffed foods at a glance. Some puffed cereals can be used not only as snacks, but also as breakfast and supper. Therefore, improve your scientific literacy, no matter what the name or classification, you can see the essence through the phenomenon, and be able to remain unchanged in the face of changes, so that you can pick out the product you really like from the overwhelmed food shelves.

References:

[1] Meng Qifan, Yuan Tiantian, Wang Jiaying, et al. Research progress on regulation and application of starch thermal expansion processing characteristics[J]. Food and Fermentation Industries, 2023, 49(02): 288-296. DOI: 10.13995/j.cnki.11-1802/ts.031188.

[2] Lin Mian, Rui Hanming, Liu Tongxun. Food puffing technology and its application [J]. Food and Fermentation Industries, 1999(03):67-70.