How to test the air permeability of food packaging bags? you need to know

As we all know, oxygen has a great influence on the quality of food, and some food packaging (such as carbonated drinks, coffee, etc.) also has strict requirements on the air permeability of carbon dioxide, so control the air permeability of food packaging materials and the organic matter inside the packaging. Gas content has also become one of the first tasks of food packaging. Next, professional flexible packaging manufacturers will analyze the impact of the air permeability of food packaging bags on food based on experience, and briefly introduce how to detect the air permeability of food packaging bags. 1. The effect of gas permeation on the quality of food 1. Oxidize the fat in the food, and this oxidation can be carried out even under low temperature conditions. The peroxide produced by the oxidation of oil not only makes food lose its edible value, but also produces odor and toxic substances. 2. Most of the bacteria in the food multiply and grow due to the presence of oxygen, resulting in the festering and metamorphosis of the food. 3. If the necessary protective measures are not taken during the storage, transportation and circulation of fresh fruits and vegetables, the fruits and vegetables will absorb oxygen and release carbon dioxide and water due to respiration, and consume part of the nutrients, resulting in overripe, soft, and flavor changes in vegetables and fruits. and so on. 4. At room temperature, the reaction rate of oxidative browning is much faster than that of heating browning. For flavored foods, such as concentrated broths and foods that are prone to oxidative browning and discoloration, even a small amount of residual oxygen can cause browning, causing the flavor of the food to be lost or degraded. 5. Carbon dioxide also has a great influence on the quality of carbonated drinks, beer, coffee, juice and other products in addition to the activation of oxygen. 2. Introduction to the main method of air permeability inspection In order to avoid the above situation, it is very necessary to conduct air permeability inspection on food packaging to ensure the gas barrier function of packaging materials. From the inspection principle, the air permeability inspection methods can be divided into two types: differential pressure method and electric quantity analysis sensor method. 1. Test principle of differential pressure method: The test chamber is divided into two independent spaces by the film to be tested, and the test gas is filled into one side (high pressure chamber) between them to form a certain pressure difference at both ends of the sample, and the gas in the high pressure chamber The permeability of the gas can be obtained by measuring the pressure or volume change of the low-pressure chamber through the membrane permeating into the low-pressure chamber. 2. The inspection principle of the coulometric sensor method uses the film to be tested to separate the inspection cavity into two independent gas flow systems, and one side is the active gas to be tested (pure oxygen or mixed gas containing oxygen can be selected, and the relative gas relative to the gas can be set. humidity) and active nitrogen on the other side. The pressure difference between the two ends of the sample is equal but the oxygen partial pressure is different. Under the effect of the concentration difference, the oxygen passing through the film is sent to the coulometric sensor under the carrying of nitrogen flow, and then the oxygen transmission rate of the material is calculated. Differential pressure method and equal pressure method have different inspection principles, different inspection conditions, and different units of test results (the unit of differential pressure method is cm3/m2•24h•0.1MPa, while the unit of isobaric method is cm3/m2•d), so the uncorrected raw data obtained by these two inspection methods are theoretically not comparable. However, after calibrating the isobaric method equipment with a standard membrane and applying the calibration factor to the formal test, the experimental results of the differential pressure method and the isobaric method can be compared. Due to the support of the membrane technology theory, the differential pressure method has always been used as a basic method in the air permeability test, and this method is mostly used by scientific research and testing organizations. Its great benefit is that there is no selectivity with respect to the check gas, and the versatility for different check gases is very good. With the development of vacuum gauge detection technology and the application of vacuum technology in equipment design, the detection accuracy of equipment and the repeatability of inspection data have been greatly improved. The sensor method appeared with the continuous maturity of oxygen detector technology. Since the sensors used are consumable components, the calibration factor obtained from equipment calibration is not effective for a long time. Periodic equipment calibration is required according to requirements, and when When the wear and tear of the sensor reaches a certain level, it must be replaced.
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