Burst bags in high-temperature cooking bags

[China Packaging Network News] High-temperature cooking bags are high-end products in flexible packaging. Why do they have high prices? There are two factors. One is high profits. Each bag has several times the profits of the same size bags; the other is high risk. Due to discoloration, reduced peel strength, and explosion of bags, many problems are caused, such as those that cause downstream manufacturers to return lost orders, and those who seriously need to compensate for a large amount of contents stored in downstream products. An analysis of the explosion problem that often occurs.

1. First analyze the boiled bag as required to fill the bag with water and seal it with air.

After careful observation, it was found that the air was not clean. The heating process before 100°C shows that the time-sealed glass ball represents the closed bag. It can be seen that the expansion of the boiled bag is normal when heated.

The reason for the analysis is as follows: water seal is installed at room temperature, and the pressure inside and outside the bag is balanced. During heating at room temperature to 98°C, the liquid water itself must expand, and the air in the bag must expand. At this time, part of the water vapor generated also occupies. Part of the space, leading to expansion.

At this time, the pressure in the bag will increase. To support the above conclusions, we used a Beijing-based Land Meike ZY-1 positive pressure tester and a DK-98-1A water bath for qualitative tests. During the heating process, the pressure in the bag did increase, and the degree of increase was The loading of the sample is related to the ratio of the residual air to the maximum volume of the bag and is somewhat related to the residual air. The ratio of water and bag is high and the pressure is high; the residual air is high and the pressure is high.

Blasting of the bag is a phenomenon in which the creep of the polymer material in the sealing area under the hot state is insufficient to support the pressure. This strength is called the hot burst strength. In order to compare the cold and hot blasting strengths, we tested the blasting strengths at different temperatures using a ZY-1 positive pressure tester at room temperature and 95°C, respectively. A spot check of the 2O group showed that the heat-sealed bags had a burst strength of 95°C at room temperature. The difference is large. The reason for the analysis is that the intensity is reduced when heat is applied. This is a normal condition encountered in our production.

If the bag is not heat-sealed, the blasting strength is very small at room temperature and it is a defective product in production. Although there is no leakage, it is more likely to burst the bag when it is heated.

2. Cooking bag problem Cooking bag is the same as the boiled bag before it is heated to 100 °C.

We have investigated cooking bags heated to 1000 (above 2 when there are no instruments in the country that can observe the cooking process. The sensors of the ZY-1 positive pressure tester cannot penetrate the T-25C back pressure cooker. We can only speculate that In a cooking pot, when the temperature exceeds 100°C, the pressure inside the bag is always higher than the pressure outside the bag (this presumption is currently not supported by facts. We are developing a cooking pot with a transparent observation window in order to solve this problem).

3. Can explosive bags be avoided?

Burst bag is the pressure inside the bag is higher than the bag outside, then there is no way to avoid this situation? From the boiling process we understand that the pressure inside the bag is not the same when the pressure is constant, if the environmental change is synchronized Can you avoid it?

We closed the exhaust of the TS-25C back pressure cooker and started to form a closed environment from the beginning of the sample. We set 115°C (because the relationship between the valve and the insurance valve cannot be set higher) and we tested 30 retort pouches. No bursting bag. It is conceivable that this is equivalent to applying an external pressure to the bag from the beginning of the heating, so that the internal and external pressures are balanced, so there is no overburden.

4. in conclusion:

(1) The problem of cooking and torpedo bags in high-temperature cooking bags is actually a problem of the hot burst strength of the bags, which is generally caused by damage to the heat-sealing parts.

(2) If an external pressure is added to the cooking bag in advance, and this relative pressure is always maintained during the heating process, the bag should not be blown, but high pressure resistance is required for the pot body, such as 135°C, and normal work resistance is required. The pressure increased from 2.2kg to 3.2kg.

In this view, the explosion of the bag is related to the test method and also related to the production method. It is important to improve the high-temperature sterilization process to reduce the burst bag. This article takes this as a guide and hopes to help improve the further improvement of food packaging.