In food packaging, vacuum sealing does not always produce the same results. Some products behave predictably, while others require closer monitoring of residual air, compression, film, sealing, and settling within the bag.
Dried fruits, legumes, grains, dehydrated products, foods containing oily components, or light mixtures may behave differently during the vacuum cycle. The issue is not limited to preservation; it also affects the shape of the bag, the stability of the pallet, and the perceived quality of the finished product.
Why Some Foods Don't Respond Well to Vacuum Sealing
Some foods are difficult to vacuum-pack because they trap air, release gas, deform under compression, or are susceptible to oxidation. In these cases, the result depends on the balance between air extraction, the film, the seal, pressure, and how the product settles in the bag.
The challenge stems from the physical properties of the material. An irregularly shaped product may leave internal voids that are difficult to eliminate; a fragile product may break if the vacuum is applied too aggressively; and an oxygen-sensitive food product may require a more effective barrier and a seal that remains stable over time.
That is why the vacuum packaging process must be designed around the actual product. The same machine can produce different results depending on changes in particle size, bulk density, residual moisture, fat content, particle shape, or bag size.
In food applications, VAI these aspects along with the configuration of the VS99 vacuum packaging or custom solutions such as the MV305, always based on the material to be packaged and the desired result.
Oxidation and Residual Gases: What to Check During the Cycle
Oxidation is one of the main reasons why many companies are considering vacuum packaging. In dry food products, the presence of oxygen can accelerate quality degradation, alter sensory characteristics, and reduce shelf life.
The problem becomes more apparent with foods that contain sensitive ingredients, such as oily nuts, seeds, legumes, grains, or dehydrated products. In these cases, reducing residual air helps protect the product, but this must be achieved without compromising the bag.
The cycle must be checked against several parameters:
- air evacuation time, to be adjusted according to the product's density and volume;
- residual pressure, which must be consistent with the required protection;
- any gradual gap, which is useful when the product tends to shift or deform;
- product settling, when the material needs to be stabilized before welding;
- the final strength of the weld, which is crucial for ensuring the result lasts over time.
With some products, the problem isn’t just the air present at the time of packaging. Some foods may release small amounts of gas over time or change in volume after being sealed. In these cases, a packaging cycle that is too rigid can result in misshapen bags, bulges, or an uneven pallet.
Film, Sealing, and Bag Forming
The film is a critical factor in vacuum packaging. It must provide a barrier that is compatible with the product, while also withstanding tensile and compressive forces, as well as the stresses generated by the vacuum cycle.
A film that is too flexible can lead to lateral deformation or bulging. A film that is too stiff, on the other hand, can create stress at the seal or fail to conform properly to the product. For this reason, the choice of material must take into account not only food safety but also the mechanical properties of the finished bag.
The sealing process is where this assessment becomes most critical. Temperature, pressure, contact time, and the cleanliness of the sealing area determine the bag’s actual seal integrity. If the product generates dust, particles, or residue in the sealing area, the risk of micro-leaks increases.
Bag deformation is often caused by a combination of factors: unbalanced vacuum, unsuitable film, an unstable package format, or a product that settles unevenly. To prevent this, VAI the choice of vacuum settings to the package design and to testing the final behavior during handling and palletizing.
For applications such as dried fruits and legumes, this attention to detail is particularly important: the bag must protect the product, but it must also be uniform, stable, and compatible with logistics.
When to Test the Actual Product Before Production
Based on the above, testing with the actual product is essential, since the material’s behavior cannot be reliably determined from the technical data sheet alone.
During pre-testing, specific parameters can be verified: vacuum level, film seal integrity, seal performance, bag deformation, final compactness, and stability during handling. This phase allows for the early correction of any issues, thereby avoiding last-minute changes during production.
The questions that need to be clarified are of an operational nature:
- Does the product retain air after filling?
- Does it compact evenly, or does it create empty pockets?
- Does the film retain its barrier properties and shape after the vacuum cycle?
- Does the weld remain stable even if there are residues in the joint area?
- Is the finished bag suitable for handling, palletizing, and transport?
Why does the vacuum-sealed bag lose its shape?
The bag may become deformed if the product settles unevenly, the film does not withstand the vacuum cycle properly, or the bag design does not distribute volume and pressure effectively. Deformation must be evaluated through actual testing of the product, film, and final weight.
How can residual gases be reduced?
Residual gases can be reduced by adjusting the evacuation time, pressure, any intermediate pauses, and sealing. For complex products, a gradual vacuum can help prevent sudden movements of the material before sealing.
What type of plastic wrap should be used for perishable foods?
The film should be selected based on its barrier properties, stiffness, weldability, and behavior under vacuum. It is not enough to evaluate the material in the abstract; it must be tested with the actual product, in the intended format, and under consistent machine parameters.
To determine whether vacuum packaging is suitable for your food product, the technical evaluation must be based on actual samples, the film type, weight, and desired format. You can contact the VAI team to set up a test that aligns with your production process.
