Frequent bag breakage occurs during the sterilization process of retort pouches. These measures can effectively reduce it.

During high-temperature sterilization of retort pouches, the residual gas inside the pouch expands, the volume of the contents increases, and the pressure inside the pouch rises. When the internal pressure exceeds the pouch's capacity, and the pressure in the retort is lower, the pouch will burst. To ensure that the retort pouch does not break during sterilization, Shunxingyuan Packaging, a professional flexible packaging manufacturer, offers some tips.

1. Adopt pressure sterilization and pressure cooling

After the retort pouch enters the sterilizer, the temperature at which air pressure is applied depends on the initial temperature of the retort pouch, the filling amount, and the amount of residual air. Generally, pressurization begins at 90 degrees. If pressurization is too early, the heating time is prolonged; if it is too late, bag breakage is likely.

The choice of sterilizing medium during sterilization is also closely related to bag breakage. Common sterilizing media include high-pressure hot water, high-pressure steam, and a mixture of steam and air. Each medium has its advantages.

Studies have shown that high-pressure hot water heats more evenly than the latter two during sterilization. However, its disadvantages are high heat consumption during heating and occasional deformation or contamination of the packaging bag. The latter two methods have almost no such disadvantages. For retort pouches, a steam and air mixture seems ideal, but the ratio of air mixed in should be appropriate. If too much, the heat transfer performance of the container is poor, and the sterilization effect is reduced. Conversely, if too little, slight pressure changes may cause bag breakage.

The relationship between the steam-to-air ratio and bag breakage varies with the size of the retort pouch, the filling amount of the contents, the amount of residual air, ( that is, the vacuum degree, ) and the sterilization temperature.

2. Packaging Strength Testing

This includes testing the sealing strength, peel strength, pressure strength, hydrostatic pressure strength, puncture strength, and drop strength.

Sealing strength reflects the firmness of the heat-sealed portion of the retort pouch. Peel strength (or composite strength) ) reflects the reliability of the lamination between layers of the retort pouch. Internal pressure strength ( burst strength ) reflects the ability to withstand internal pressure. Hydrostatic pressure strength ( external pressure strength ) reflects the strength of a filled retort pouch to withstand external static pressure. Puncture strength reflects the strength of the retort pouch to withstand sharp object pressure. Drop strength reflects the allowable drop height of a sealed retort pouch filled with contents during handling and transportation.

To ensure sealing strength, it is crucial to avoid contaminating the sealing area of the retort pouch when filling the product. If there are juices, water droplets, etc., attached to the inner side of the sealing area, the area cannot be sealed.

The evenness of the pouch sealing area also affects sealing quality. To keep the sealing area flat and wrinkle-free after sealing, the following points should be noted: the pouch opening must be flat and the two sides must be of equal length; the sealing machine mold must be flat and parallel, and the fixture must be good. ; The contents should not be too large, the filling amount should not be too much, and the total thickness of the pouch should not exceed the limit.

The sealing temperature, pressure, and time should be determined based on the constituent materials of the retort pouch, the melting temperature of the film, and the thickness of the seal. Within a certain sealing time, a temperature that is too low will result in incomplete melting and poor adhesion, while a temperature that is too high will cause excessive melting of the film, altering its physicochemical properties and resulting in poor sealing.

Similarly, too low pressure will result in insufficient bonding of the melted film, while too high pressure may cause extrusion of the melted film material, resulting in poor sealing. Sealing time determines production capacity. Given the premise of ensuring sealing quality, sealing time determines production capacity, and vice versa. Generally, sealing temperature, pressure, and time should be tested.

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