How can you vacuum pack something?

Answer

Hello Lotte,

Actually, it’s not that hard to do. Briefly explained, you place a product in a packaging (e.g. a bag), remove the air in the bag by applying low pressure (using a vacuum pump) and then close the packaging (e.g. seal it under the influence of heat).

There are of course many different options for doing this:

• You can vary in packaging. For example, there are “shrink films” that close very tightly around your product under the influence of heat, and in the industry the bag can still be formed with large rolls of plastic film and that film is melted together in the right places with the product in between.
• You can vary in vacuum (under) pressure. Depending on how low the pressure is that is applied and how long it is maintained, more gas is removed, also for example from pores/cavities in the product. You can understand that more gas is “trapped” in eg bread than in a piece of chocolate. Residual gases in the product will return to equilibrium with the environment in the packaging and the vacuum appearance may then be lost.
• You can use different machines. Here in our lab there is a small vacuum chamber where you pack packages one by one. In industry things have to go much faster, so there are automatic systems, sometimes even with several vacuum chambers at the same time.

The purpose of vacuum packaging can also be different. When it comes to foodstuffs, attempts are often made to extend the shelf life of products by removing air (and therefore oxygen). As a result, certain micro-organisms can no longer grow, certain chemical processes can no longer continue, etc. A product also takes up much less space, which can save costs during transport and storage. In addition, it is also sometimes used in the kitchen for vacuum cooking products at a low temperature (sous-vide).

Another form of vacuum packaging is, for example, “canning”. You may be familiar with the glass preserving jars with a glass lid, metal bracket and rubber (often red) ring. These are used (now less than in the past) to “preserve” products. This also ensures a longer shelf life. The jars are filled, sealed and sterilized in a water bath. The heat causes the air in the pot to escape (it expands = overpressure). After cooling, an underpressure is then created. The ring keeps the jar airtight under low pressure after cooling. When opening, pull the rubber ring to break the vacuum and hear the air enter.

Hopefully this answer already gives you an idea of ​​how vacuum packaging works. You can even go one step further and introduce gases other than air into the packaging. Then this is called gas packaging or modified atmosphere packaging. This may be necessary as an extra storage step or to store fragile products such as crisps, which would break when vacuum packed.

Greetings,
Dries