Analysis of the explosion bag problem of high temperature cooking bags

1. First, analyze the boiled bag and put the water into the bag according to the regulations, and vent the seal. After careful observation, we found that the air was not cleaned. Its heating process before 100 ° C shows that the time-sealed glass ball represents a closed bag, and it can be seen that the expansion of the boiled bag during heating is normal. The reason for the analysis is that the water seal is filled at room temperature, and the pressure inside and outside the bag is balanced. During the heating to 98 ° C at room temperature, the liquid water itself is expanded, and the air in the bag is expanded, and part of the water vapor generated at this time also occupies. Part of the space, causing expansion. At this time, the pressure inside the bag will increase. In order to support the above conclusions, we used Beijing Randmeke's ZY-1 positive pressure tester and DK-98-1A water bath to conduct qualitative tests. During the heating process, the pressure inside the bag is indeed rising, and the degree of increase and The loading of the sample is related to the residual air to the maximum volume ratio of the bag, and is related to the amount of residual air. The ratio of water to bag is high, and the pressure is high; the residual air is high and the pressure is high. The blasting of the bag is caused by the creep of the polymer material in the sealing part under such a hot state, which is insufficient to support the pressure. This strength is called thermal bursting strength. In order to compare the hot and cold blasting strength, we used ZY-1 positive pressure tester to test the blasting intensity at different temperatures at room temperature and 95 °C respectively. The 2O group was found to compare the heat-sealed bag, and the bursting strength at room temperature was 95 °C. The difference is large. The reason for the analysis is the decrease in strength when heated. This is the normal situation encountered in our production. If the bag is not heat-sealed, the bursting strength is small at normal temperature, which is a defective product in production. Although there is no leakage, it is more likely to burst when heated.

2. The retort pouch retort pouch is the same as the boiled pouch before it is heated to 100 °C. We investigated the cooking bag when it was heated to above 100 °C. Because there is no instrument in China that can observe the cooking process, the sensor of ZY-1 positive pressure tester can not penetrate into the T-25C back pressure cooking pot. We can only speculate that In the cooking pot, when the temperature exceeds 100 °C, the pressure inside the bag is always higher than the pressure outside the bag (this speculation is currently not supported by fact, we are developing a cooking pot with a transparent observation window to solve this problem).

3. Can the explosion bag be avoided? The explosion bag is that the pressure inside the bag is higher than the bag. Is there any way to avoid this? From the boiling process, we know that the pressure in the bag is high and the pressure is constant. Bags, if you let the environment change synchronously can not be avoided. We closed the exhaust of the TS-25C back pressure cooker, and formed a closed environment from the sample. Set 115 °C (cannot be set higher because of the safety valve relationship), and test 30 retort bags. No explosion bag. It is conceivable that this is equivalent to applying an external pressure to the bag from the start of heating to balance the internal and external pressures, so there is no bursting bag.

4. Conclusion: (1) The problem of cooking and blasting of high-temperature cooking bags is actually the thermal explosion strength of the bag, which is generally caused by damage to the heat seal. (2) If an external pressure is added to the retort pouch in advance, and this relative external pressure is maintained during the heating process, the blast bag should not occur, but the pressure resistance of the pot body is high, such as 135 ° C, which requires normal working resistance. The pressure increased from 2.2 kg to 3.2 kg. In this way, the explosion bag is related to the test method and also related to the production mode. It is important to improve the high temperature sterilization process to reduce the explosion of the bag.