Modified Atmosphere Packaging (MAP) means that in a certain closed packaging, the gases in the packaging are different from the normal atmospheric composition through various adjustments, so as to inhibit the physiological and biochemical reactions, physical reactions and oxidative browning that cause deterioration of food quality, so as to achieve the purpose of prolonging food preservation and long-term preservation. Generally, one or more gases, such as carbon dioxide, nitrogen and oxygen, are filled into the package in a certain proportion by a continuous thermodynamic inflatable machine, and the gas filling package is completed after sealing by hot pressing.
Effect of Modified Atmosphere Packaging
A large number of practices have proved that the application of reasonable modified atmosphere packaging, especially the appropriate proportion of filling gas, not only helps to limit the growth of microorganisms in packaging, but also has a positive significance for alleviating the excessive maturity and oxidation of content.
Carbon dioxide is an important gas component in modified atmosphere packaging. Its prominent effect is its highly effective bacteriostatic effect. Carbon dioxide can penetrate bacterial cells, reduce PH and enzyme activity in cells, thus inhibiting cell proliferation, and thus has antiseptic and antifungal effects on fish and seafood, fresh and tender fruits and vegetables, baked snacks and so on.
Nitrogen is a colorless and tasteless inert gas, which does not react with food chemically. Nitrogen filling is used as filling gas to keep the color, aroma, taste, crispness and shape of food. It can also alleviate the oxidation of oil.
Oxygen is an important condition for the growth and reproduction of most organisms, and it is also the main inducement of oxidative deterioration of lipids. Generally speaking, the modified atmosphere packaging is not filled with oxygen, but for some foods, a certain amount of oxygen has a good effect on maintaining the properties of other aspects of food.
For example, fish and seafood often contain myoglobin, which is purple red. Oxygen binds with myoglobin to produce oxymyoglobin, which makes the meat bright red. However, a large amount of oxygen can also accelerate fat oxidation and microbial reproduction in meat. Therefore, the modified atmosphere packaging of this kind of food is suggested to fill the mixture of oxygen and carbon dioxide to achieve dual effects by the Bacteriostasis of carbon dioxide.
For another kind of fresh fruit and vegetable food, the concentration of oxygen should be lowered as much as possible in order to reduce the respiratory intensity and matrix oxidation loss of food and delay maturation, but too low oxygen concentration will cause anaerobic respiration of fruit and vegetable on the one hand, leading to anoxic disorder, on the other hand, it will cause anaerobic fermentation, such as Botulinum toxin, etc. Because different fruits and vegetables have different critical oxygen concentration, it is necessary to set the filling oxygen amount according to the type of fruits and vegetables when using modified atmosphere packaging.
Analysis of Factors Affecting the Effect of Modified Atmosphere Packaging
The effects of modified atmosphere packaging are mainly reflected in three aspects: bacteriostasis; inhibition of respiration and maturity for fresh fruits and vegetables; preservation of the original taste and shape of food, especially baked food, to reduce the odor caused by oil oxidation. From food packaging to transportation and storage, the effect of modified atmosphere packaging is restricted by many factors, including the selectivity of carbon dioxide bacteriostasis, the concentration of carbon dioxide and the properties of modified atmosphere packaging materials.
Effect of selectivity of carbon dioxide bacteriostasis on modified atmosphere packaging
According to the demand of microbial metabolism for oxygen, it can be divided into aerobic, facultative and anaerobic microorganisms.
Aerobic microorganisms refer to organisms that can grow normally only under aerobic conditions. They contain some aerobic bacteria and fungi. For these microorganisms, carbon dioxide concentration below 10% can inhibit their growth. The inhibition effect of carbon dioxide on different fungi is also different, for example, Penicillium is more tolerant to carbon dioxide than Aspergillus.
Facultative anaerobic microorganisms are microorganisms that can survive in both aerobic and anaerobic environments, such as yeasts. When oxygen is scarce, these microorganisms survive by converting sugars into carbon dioxide and ethanol, so the inhibition of carbon dioxide on them will be reduced.
Anaerobic microorganisms refer to microorganisms that grow better under anaerobic conditions than under aerobic conditions. For example, Clostridium fusiforme multiplies rapidly under anaerobic conditions, decomposes sugars, and causes gas production and protein deterioration of fruits and vegetables. If such microorganisms exist, filling a large amount of carbon dioxide into packaging will promote the reduction of oxygen content in packaging system, but it is not conducive to inhibiting the growth of such microorganisms.
Effect of Carbon Dioxide Content on Modified Atmosphere Packaging
According to the above analysis of the effect of modified atmosphere packaging, the effect of filling carbon dioxide varies with the contents of packaging. Previous studies have shown that increasing carbon dioxide content can enhance its ability to inhibit microbial reproduction, and with the increase of carbon dioxide content, the inhibition will gradually increase. At the same time, the filling concentration should be determined according to the initial microbial species and quantity of the content.
If the initial microorganisms in the content are mainly aerobic bacteria or fungi, the inhibition effect can be shown by filling less than 10% carbon dioxide. 20% – 30% carbon dioxide can better inhibit most aerobic microorganisms. When the content of carbon dioxide reaches more than 50%, the enhancement of the inhibition effect is no longer significant. For modified atmosphere packaging of fruits and vegetables, 2%-3% carbon dioxide is the best filling.
The influence of packaging materials on the effect of modified atmosphere packaging
After finished, the composition and content of internal gas will remain stable for a period of time. With the prolongation of product storage time, the content of oxygen, carbon dioxide or nitrogen in packaging will gradually change, thus affecting the original packaging effect and even the quality of products.
Generally, the main reasons for the change of gas content are gas permeation and leakage. Gas permeation means that the gas enters the surface of packaging material from the high concentration side and diffuses to the low concentration side. The effect of gas infiltration/leakage through this channel on the gas composition in packaging is long and slow, and its penetration rate depends on the barrier performance of packaging materials. Leakage refers to the rapid change of gas content caused by gas entering or escaping through tiny holes or cracks in the heat-sealing part of packaging.
Whether it is gas permeation or leakage, it will affect the content of each gas component in the modified atmosphere packaging, thus affecting the quality of products. Therefore, enterprises have also adopted a variety of gas control methods, such as the use of high barrier packaging materials to slow down gas penetration.
As carbon dioxide plays a major role in modified atmosphere packaging, the selected packaging materials should show a good barrier effect to carbon dioxide. Four kinds of commonly used materials for modified atmosphere packaging were selected, namely PET, KPET, BOPP and VMBOPP. Carbon dioxide permeation test was carried out by VAC-V2 differential pressure gas permeameter.
With the widespread use of modified atmosphere packaging, filling suitable gases for different contents to make the best effect is the most important thing in the production and application of modified atmosphere packaging nowadays. In the application of modified atmosphere packaging, filling gas, especially carbon dioxide, its bacteriostatic selectivity and concentration, as well as the choice of packaging materials will have an impact on the effect of modified atmosphere packaging. Packing manufacturers and users need to pay more attention to it.
Modified atmosphere packaging machines
For high quality & high efficiency MAP modified atmosphere packaging machines, KANGBEITE PACKAGING supplies 3 series of machines, which are semi-auto tray sealing machine, inline tray sealing machine, and fully automatic thermoforming packaging machine, all the machines have the options for modified atmosphere packaging.
- Semi-auto tray cup sealer for modified atmosphere packaging
- Inline automatic tray sealing machine for modified atmosphere packaging
- Fully automatic thermoforming packaging machine for modified atmosphere packaging