Why Does Vacuum Packaging Leak After Being Left For A Period Of Time

Why does vacuum packaging leak after being left for a period of time?
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Opening the refrigerator, I found that the vacuum packaged braised food was bulging, and when I opened the vacuum mixed grain bag I purchased online, there was a sound of air leakage. This kind of 'failure' scenario is not uncommon in daily life. Why does vacuum still leak? The seemingly simple sealing structure of vacuum packaging is actually the result of the combined effects of material properties, process control, and environmental factors. Air leakage is often the concentrated outbreak of multiple hidden dangers.
1, Material hazards
Packaging materials are the first line of defense against air leakage, and their inherent defects often become the source of air leakage. Insufficient thickness packaging bags will stretch excessively at the protrusions of irregular products during vacuum pumping, forming pinholes that are difficult to distinguish with the naked eye. There have been meat product manufacturers who experienced significant air leakage in a short period of time after packaging bone products due to insufficient thickness of the packaging bags used. After replacing with thicker composite films, the air leakage situation significantly improved.
The insufficient barrier properties of the material make it more concealed. Packaging bags with ordinary structures such as OPP/PE have weak gas barrier capabilities, and after a period of vacuuming, the vacuum degree will significantly decrease. If there are residual crystal points in the aluminum-plastic composite film during the production process, it will directly damage the integrity of the barrier layer and provide a channel for gas to penetrate. In addition, differences in compatibility between different materials can also pose hidden dangers.
2, Process defects
Sealing is the lifeline of vacuum packaging, but even slight deviations in the heat sealing process can lead to air leakage in the later stages. A certain nut factory once experienced widespread air leakage during transportation due to the sealing temperature not meeting the standard. After inspection, it was found that only partial adhesion was formed at the sealing area, and it was not completely sealed. A more common problem is the inclusion of impurities during sealing, such as oil seeping from braised dishes and powder from miscellaneous grains, which can hinder the tight fusion of plastic film and affect the sealing effect.
Excessive vacuuming also carries hidden risks. Some producers believe that 'the cleaner you draw, the better', but in fact, it can disrupt the tension balance of the packaging bag, especially for materials with poor elasticity, which are prone to fatigue rupture during storage after excessive stretching. The "false seal" formed by the folding of the seal is even more difficult to detect, and even if the heat sealing temperature is increased, it cannot completely avoid the occurrence of pinholes, leaving hidden dangers for subsequent air leaks.
3, Content and Environment
The characteristics of packaged items often become a "booster" for air leakage. Products with sharp edges such as pork bones and fried peanuts will continue to squeeze the packaging bags during storage and transportation, causing progressive puncture damage and air leakage over time. The chemical changes in food itself are more concealed: if meat products are not thoroughly sterilized, bacterial growth will produce gases such as hydrogen and carbon dioxide, which will cause bag swelling and impact the sealing layer, leading to air leakage.
Environmental factors will accelerate the process of gas leakage. Severe temperature changes can cause the packaging material to repeatedly expand and contract, leading to gradual cracking of the sealing edge; A humid environment can accelerate the aging rate of plastics, causing a decrease in material strength and making it more prone to damage. A certain pickled product company once stored its products in an open-air warehouse, and during high temperatures in summer, there was a significant increase in air leakage compared to when stored in a constant temperature warehouse. In addition, bumps and collisions during transportation can directly cause physical damage to the packaging bag, with wrinkles and sharp corners being the most vulnerable areas.
The sealing performance of vacuum packaging is like a precise balancing system, and any omissions in any link will become apparent over time. Therefore, to solve the problem of gas leakage, it is necessary to establish a full chain control. When selecting materials, appropriate materials should be matched according to the characteristics of the product. In terms of process, strict control of heat sealing temperature, pressure, and time is required to ensure a smooth and impurity free seal. In the storage and transportation process, use size adapted cardboard boxes to avoid damage to the packaging bags due to excessive compression. Consumers can also pay attention to details when purchasing, observing whether there are wrinkles at the corners of the packaging bag and whether the sealing is flat. These are intuitive criteria for judging the sealing performance.