Modified atmosphere packaging is also known as MAP or CAP, domestically called modified atmosphere packaging or replacement gas packaging, and inflatable packaging. Commonly used gases are N2, O2, CO2, mixed gases, and the like. Modified atmosphere packaging technology can be widely used for the preservation of various foods, extending the shelf life of food and enhancing the value of food. This paper mainly introduces the role of various gases in modified atmosphere packaging and how to control the quality of modified atmosphere packaging. I. The role of different gases in modified atmosphere packaging
1. Application of CO2 in food modified atmosphere packaging The application effect of CO2 modified atmosphere packaging in meat packaging is obvious. High concentration of CO2 can hinder the reproduction of microorganisms such as aerobic bacteria and mold, and prolong the stagnation period and index of microbial growth. During the growth period, it acts as a preservative and mildew. In particular, the method allows fresh meat products to be stored for 120 days without the need for freezing. This method is currently used in meat exporting countries such as the United States and Australia.
2, the application of nitrogen in food packaging Nitrogen-filled packaging is mainly used in fried potato chips and French fries, oil cooking food. Nitrogen (N2) is an ideal inert gas. It has special effects in food packaging: it does not react with food and is not absorbed by food. It can reduce the oxygen content in the package and greatly inhibit the growth and reproduction of bacteria, molds and other microorganisms. To slow down the oxidative deterioration and decay of food, so as to keep food fresh. At the same time, the nitrogen-filled packaged food can also prevent the food from being crushed and broken, the food is bonded or shrunk, and the geometric shape, dryness, crispness, color and aroma of the food are maintained.
3, the application of composite (mixed) gas in modified atmosphere packaging foods Composite gas is generally O2, N2 mixed or CO2, N2, O2 mixed form, mainly the use of different gases to achieve the purpose of quality and preservation. The composite modified atmosphere packaging is collectively referred to as MAP packaging in the world. The modified atmosphere is generally composed of CO2, N2, O2 and a small amount of special gases. 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, maintains the color of fresh meat, maintains the oxygen-rich breath 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, the preservation requirements and the packaging materials, so as to achieve the effect of high preservation quality of the packaged food, good maintenance of the nutrients, real ability to achieve the original traits, and delaying the shelf life of the fresh-keeping. For example: modified atmosphere of fresh fish and shrimp fresh aquatic products and marine fish metamorphism mainly bacteria to decompose the fish's oxidized trimethylamine to release the taste of trimethylamine, fish fat oxidation rancidity, fish body enzymes degraded fish soft, fish Body surface bacteria (aerobic Escherichia coli, anaerobic Clostridium) produce poisoning toxins that endanger human health. The gas used for modified atmosphere packaging of fish is composed of CO2, O2 and N2. The concentration of CO2 gas is higher than 50%, which inhibits the growth of aerobic bacteria and mold without causing the fish to seep out; the concentration of O2 is 10%-15%. Oxygen bacteria reproduction. The fish's cockroaches and internal organs contain a large amount of bacteria, which must be removed, cleaned and disinfected before packaging. Because CO2 easily oozes out plastic film, the packaging material of fish modified atmosphere packaging needs to use a composite plastic film with high gas barrier property, which can be maintained for 15-30 days at 0 °C - 4 °C. British tuna uses 35% - 45% CO2 / 55% - 65% N2 gas fresh-keeping packaging shelf life of 6 days.
The deterioration of shrimp is mainly caused by microorganisms. Its intrinsic enzyme action causes the shrimp to darken. The grass shrimp can be kept fresh in a modified atmosphere package. The shrimp was first immersed in a preservative solution of 100 mg/L lysozyme and 1.25% sodium hydrogen sulfite, and then inflated with 40% CO2 and 60% N2 mixed gas, and the shelf life was longer than that of the control sample. The extension was 22 days, which was 6.5 times the shelf life of the control sample.
Second, the introduction of modified atmosphere packaging testing items and testing equipment has just introduced the specific application of modified atmosphere packaging, in order to ensure the effect of modified atmosphere packaging, it is necessary to control the proportion of gas content in the packaging (top air body analysis), at the same time need to The quality control is carried out on the packaging to avoid the quality problem during the product warranty period due to the disorder of the internal gas of the package due to the cracked packaging or poor barrier performance. Labthink (Jinan Languang Electromechanical Technology Co., Ltd.) is an excellent provider of testing instruments and inspection services. In order to enable the relevant units to deeply solve the quality control projects and means.
1. Top air body analysis:
The analysis of the headspace gas is essential. The test can be carried out by means of Labthink's HAG-01 top air analyzer to ensure that the proportion of oxygen, carbon dioxide and mixed gas in the packaging container is up to standard.
2, thickness detection:
Whether the film thickness is uniform or not is the basis of the performance of the air-conditioning 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. There are various methods for measuring the thickness. The test can be used to refer to GB/T 6672 plastic film and sheet thickness measurement mechanical measurement method (GB/T 6672-2001, idt ISO 4593).
The thickness measurement can be carried out using Labthink's CHY-C2 and CHY-CA thickness gauges, which are all high-precision testers that meet the requirements for antibacterial active film thickness measurement. The test resolution is up to 0.1 micron; in addition to the high precision and high efficiency of the CHY-C2 type, the CHY-CA thickness gauge adopts the automatic forward drive system for measuring samples, which greatly improves the test efficiency and fully satisfies the user. Requirements for continuous and efficient testing.
3. Anti-pendulum impact test:
The control of the impact resistance of the modified atmosphere packaging film can prevent the damage of the packaging surface due to insufficient toughness, and effectively avoid the leakage or deterioration of the product caused by the impact resistance or the drop performance of the packaging material during the circulation. .
The anti-pendulum impact test shall be carried out in accordance with GB/T 8809-1988 "Plastic film anti-pendulum impact test method", Labthink blue light FIT-015.1 water decompression method: this method can be in accordance with GB/T 15171-94 "soft packaging For the test of the sealing performance test, the Labyink MFY-01 sealing tester is used as an example. The instrument adopts the equipment of water decompression principle. The test procedure is as follows: put a proper amount of distilled water in the vacuum tank to package Put the vacuum tank into the lower side of the pressure plate to completely immerse the package into the water; then set the vacuum pressure and time of the test, generally set the vacuum degree to 20, 30, 50, 90 kPa and so on. The vacuum was stopped when a certain degree of vacuum was reached, and the time for maintaining the vacuum was 30 seconds. The test is started, the vacuum chamber is evacuated, and the sample immersed in water is subjected to internal and external pressure difference, and the gas escape condition in the sample is observed to determine the sealing performance of the sample. The film impact tester performs this standard and is more advanced than other instruments. For example, the sample clamping and the release of the pendulum are pneumatically controlled. The similar instruments currently seen are manual clamping samples; the pneumatic clamping is fast and efficient, and the clamping force on the four-shot of the film is uniform. It is not easy to produce slippage of the sample during impact and affect the accuracy of the test results. In addition, the precision is as high as 0.001J. The film impact tester that can be seen at present is basically mechanical. The data is read from the scale of the dial with low precision.
4, tear resistance test:
The product package may be torn by external force during storage and transportation. Sufficient tear propagation resistance can reduce the transmission of tears and avoid leakage problems. The tear resistance test can be carried out according to the Elmendorf method, and the test method for tear resistance of plastic films and sheets of GB/T 11999-1989 (I SO 6383-2) should be carried out. Labthink's SLY-S1 tear meter can be used for testing. The instrument uses computer control and display, as well as computer level adjustment technology to ensure accurate and reliable test data; the unique "three-circle" analysis technology can help users to visually analyze and evaluate data.
5, sealing performance test:
Sealing performance testing is extremely important for modified atmosphere packaging. If a leak occurs, the product packaging protection will be lost. The term "sealing property" refers to the property of the packaging bag to prevent other substances from entering or the contents from escaping. There are two methods for commonly used detection methods:
5.2 Positive Pressure Detection Method: Take Labthink's LSSD-01 leakage and seal strength tester as an example. The instrument is tested by positive pressure method. By applying pressure to the inside of the package, the pressure resistance, sealing degree and leakage index of the flexible package are detected, thereby achieving the purpose of detecting the integrity and sealing strength. During the test, high-pressure gas is injected into the package to quantitatively check the sealing performance and the leakage amount.
6, barrier performance test:
Barrier refers to the barrier effect of packaging materials on permeates such as gases and liquids. The barrier performance is not good, the outside gas will penetrate into the inside of the package, affecting the proportion of gas, and thus speeding up the deterioration of the product. This is completely contrary to the original intention of the air-conditioning to extend the shelf life and product quality, so it is necessary to do a good job of detecting the barrier performance. .
The detection barriers are respectively implemented in GB 1038 "Plastics film and sheet gas permeability test method - differential pressure method" and GB 1037 "plastic film and sheet water vapor permeability test method - cup method", can use Labthink blue light VAC series Differential pressure gas permeation instrument or PERME OX2/230 oxygen transmission rate test system, water vapor barrier performance can be used Labthink blue light TSY-T series moisture permeability tester or PERME W3/330 water vapor transmission rate test system.