The instrument for measuring the oxygen permeability of the special film of modified atmosphere packaging is extremely important in the field of research and application of modified atmosphere packaging. The modified atmosphere packaging is also called MAP or CAP in foreign countries, modified atmosphere packaging or replacement gas packaging and inflatable packaging in China. Commonly used gases are N2, O2, CO2, mixed gas, etc. Modified atmosphere fresh-keeping packaging technology can be widely used for the preservation of various types of food, extend the shelf life of food, and enhance the value of food. In conjunction with the corresponding technical literature, this office introduces the role of various gases in modified atmosphere packaging and how to control the quality of modified atmosphere packaging

1. The role of different gases in modified atmosphere packaging

1. Application of CO2 in modified atmosphere packaging of food

The application effect of CO2 modified atmosphere packaging in meat packaging is more obvious. High concentration of CO2 can hinder the reproduction of aerobic bacteria and mold and other microorganisms, prolong the stagnation period and exponential growth period of microbial growth, and play a role in antiseptic and mildew prevention. In particular, this method enables fresh meat products to be stored for 120 days without freezing treatment.

2. Application of nitrogen in food packaging

Nitrogen-filled packaging is mainly used in fried potato chips and chips, oil cooking food, etc. Nitrogen (N2) is an ideal inert gas and has a special effect in food packaging: it does not react with food and is not absorbed by food, can reduce the oxygen content in the package, and greatly inhibit the growth and reproduction of microorganisms such as bacteria and mold , Slow down the oxidative deterioration and decay of food, so as to keep food fresh. At the same time, nitrogen-filled food can also prevent food from squeezing and crushing, food sticking or shrinking, and maintain the advantages of food geometry, dryness, crispness, color, flavor and so on.

3. Application of compound (mixed) gas in modified atmosphere packaged food

The compound gas is mainly in the form of O2, N2 mixing or CO2, N2, O2 mixing, using different functions of different gases to achieve the purpose of quality and freshness preservation. Compound modified atmosphere fresh-keeping packaging is collectively called MAP packaging in the world. The modified atmosphere fresh-keeping gas generally consists of CO2, N2, O2 and a small amount of special gas. Among them, CO2 can inhibit the growth and reproduction of most aerobic spoilage bacteria and molds; O2 inhibits the growth and reproduction of most anaerobic spoilage bacteria, maintaining the color of fresh meat, maintaining the oxygen-rich breathing and freshness of fresh fruits and vegetables; N2 is used as filling gas. The composition ratio of the composite gas is appropriately selected according to the type of food, preservation requirements and packaging materials to achieve the effect of high quality preservation of the packaged food and good nutritional content, which can truly achieve the original characteristics and delay the shelf life of the freshness preservation.

2. Introduction of modified atmosphere packaging testing items and testing instruments

Just introduced the application of modified atmosphere packaging, in order to ensure the effect of modified atmosphere packaging, it is necessary to detect the proportion of gas in the packaging (headspace gas analysis), at the same time, we need to do quality control on the packaging to avoid packaging cracking or barrier performance Poor quality caused by the imbalance of the gas inside the package and quality problems.

1. Headspace gas analysis

Headspace gas analysis and testing is very important. The HAG-01 headspace gas analyzer can be used for testing to ensure that the proportion of oxygen, carbon dioxide, and mixed gas in the packaging container is well controlled.

2. Thickness detection:

Whether the thickness of the film is uniform is the basis of the performance of the modified atmosphere packaging film. The uneven thickness will not only affect the tensile strength and barrier properties of the film, but also affect the subsequent processing of the film. Thickness testing should refer to GB / T 6672 Plastic film and sheet thickness determination mechanical measurement method (GB / T 6672-2001, idt ISO 4593). CHY-C2 thickness gauge can be used for thickness testing, which can meet the requirements of antibacterial active film thickness testing with high precision.

3. Impact resistance test

The control of impact resistance of modified atmosphere packaging can prevent the packaging surface from being damaged due to insufficient toughness, and effectively avoid the problem of product leakage or deterioration caused by the damage of the packaging material due to the impact resistance or poor drop performance of the packaging material during the circulation process.

The pendulum impact resistance test shall be performed in accordance with GB / T 8809-1988 "Plastic film anti-pendulum impact test method". The FIT-01 film impact tester may be used to implement this standard to meet the requirements of fully automatic testing.

4. Tear resistance test

Product packaging may be torn due to external forces during storage and transportation. Sufficient resistance to tear expansion can reduce the transmission of tears to avoid problems caused by leakage.

The tear resistance test can refer to the Elmendorf method, and the GB / T 11999-1989 (I SO 6383-2) plastic film and sheet tear resistance test method should be implemented. During testing, a tear meter can be used for data analysis and evaluation.

5. Sealing performance test

Sealing performance testing is extremely important for modified atmosphere packaging. If leakage occurs, the protective effect on the packaging of the product will be lost.

There are two commonly used detection methods:

1) Decompression method in water: This method can be tested in accordance with GB / T 15171-94 "Test Method for Sealing Performance of Flexible Packages". The MFY-01 sealing tester can be used, and equipment using the principle of decompression in water. The test process is as follows: Put appropriate amount of distilled water in the tank, put the package into the vacuum tank and build it under the pressure plate to completely immerse the package in water; then set the vacuum pressure and time of the test, generally set the vacuum degree to 20, 30, 50, 90 kPa, etc. When a certain vacuum degree is reached, the evacuation is stopped, and the time for maintaining the vacuum degree is 30 seconds. Start the test, evacuate the vacuum chamber, make the sample immersed in water generate internal and external pressure difference, observe the gas escape inside the sample, and then judge the sealing performance of the sample.

2) Positive pressure detection method: test with LSSD-01 leak and seal strength tester. By applying pressure to the inside of the package, the pressure resistance, sealing degree and leakage index of the flexible package are detected, so as to achieve the purpose of detecting its integrity and seal strength.

6. Barrier performance testing

Barrier property refers to the barrier effect of packaging materials on gas, liquid and other permeates. The barrier performance is not good, the outside air will penetrate into the inside of the package, affecting the ratio of the gas, thereby accelerating the deterioration of the product, which is completely contrary to the original intention of extending the shelf life and product quality through modified atmosphere, so the barrier performance Detection.

To test the barrier performance, GB 1038 "Test method for gas permeability of plastic films and sheets-differential pressure method" and GB 1037 "Test method for water vapor permeability of plastic films and sheets-cup method" can be used. VAC series pressure difference can be used Method gas permeameter or PERME OX2 / 230 oxygen permeability test system; water vapor barrier performance can use moisture permeability tester or 0 water vapor permeability test system.

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