During daily use or product storage, have you ever encountered a sudden bulge of the aluminum foil sealing film at the mouth of the packaging bottle, like a "small Mantou"? This not only affects the appearance, but also raises doubts about the quality of the product. 

The bulging of the sealing film is essentially a phenomenon caused by the pressure inside the bottle being greater than the pressure outside the bottle. Behind it are both normal product characteristics and potential quality risks. This issue can be understood from two dimensions: "normal bulging" and "abnormal bulging". 

Today, let's first take a look at "normal bulging", which means there is no need to worry excessively about bulging. 

These types of bulges are usually caused by physical or chemical changes and do not indicate product deterioration. 

1. Altitude and pressure changes ("altitude sickness") 

Reason: When products packaged in plain areas are transported or carried to higher altitude areas, the relative pressure inside the bottle increases due to the decrease in external atmospheric pressure, causing the sealing film to lift up. This is a normal physical phenomenon. 

Features: The bulges are usually uniform and smooth, and the product itself has no other abnormalities. 

2. Product fermentation produces gas

Reason: For products such as soy sauce, vinegar, sauces, enzymes, etc. that contain active bacteria or can continue to ferment, there may still be weak fermentation activity after packaging, producing small amounts of carbon dioxide and other gases. 

Characteristics: The bulging process is slow and usually remains stable within the shelf life. 

3. Thermal expansion and contraction 

Reason: The product is hot during filling (hot filling), and after cooling, negative pressure will be generated inside the bottle, causing the sealing film to sink. But if it is placed in a high temperature environment (such as exposure to sunlight) afterwards, the air and liquid inside the bottle will expand due to heat, causing an increase in pressure and pushing the originally sunken sealing film back into a bulging state. 

Characteristic: The degree of bulging will change with temperature. 

The aluminum foil sealing film produced by Leadtra Packaging has many advantages such as strong sealing barrier, good tear off effect, bright colors, exquisite appearance, green environmental protection, high safety, strict testing, and stable quality. The effect is very reliable. If you are interested in or have any questions about us, please feel free to call us for consultation.