The Influence of The Selectivity of Carbon Dioxide Antibacterial Action on The Effect of Modified Atmosphere Packaging

Aerobic packaging refers to the process of placing food in a sealed container under specific conditions, where various adjustments are made to the packaging gas to make it different from the normal atmospheric composition. This is done to prevent the deterioration of food quality and physical reactions such as oxidation and browning, thereby achieving the goal of extending food preservation and long-term storage.

Usually, one or more gases, such as carbon dioxide, nitrogen and oxygen, are filled into the packaging in a certain proportion through a continuous thermodynamic filling machine. After being heat-sealed, the filling and packaging process is completed.

The effect of controlled atmosphere packaging

A large number of practical experiences have shown that the application of reasonable controlled atmosphere packaging, especially with the appropriate proportion of filling gases, not only helps to limit the growth of microorganisms within the package, but also has a positive effect on alleviating the excessive ripening and oxidation of the contents.

Carbon dioxide is a crucial gas component in controlled atmosphere packaging. Its prominent function lies in its highly effective antibacterial effect. Because carbon dioxide can penetrate the cells of bacteria, causing a decrease in the pH inside the cells and a reduction in the activity of enzymes, it inhibits the reproduction of cells. Therefore, it has the functions of preserving and preventing mold growth for fish and seafood, fresh and tender fruits and vegetables, and baked pastries.

Nitrogen is a colorless and odorless inert gas that does not react chemically with food. The purpose of filling food with nitrogen is to serve as a protective gas, maintaining the color, aroma, taste, crispness and shape of the food. It can also help alleviate the oxidation of oils.

Oxygen is an essential condition for the growth and reproduction of most living organisms, and it is also the main cause of oxidation and deterioration of fats. Generally speaking, in controlled atmosphere packaging, oxygen is not filled, but for certain foods, a certain amount of oxygen has a good effect in maintaining other properties of the food.

For example, foods such as fish and seafood often contain myoglobin, which is purple in color. The role of oxygen is to combine with myoglobin to form oxyhemoglobin, making the meat appear bright red. However, a large amount of oxygen will also accelerate the oxidation of fat and the reproduction of microorganisms in the meat. Therefore, for the airtight packaging of these foods, it is recommended to fill a mixture of oxygen and carbon dioxide, using the antibacterial effect of carbon dioxide to achieve a dual effect.

For another type of fresh fruit and vegetable foods, the concentration of oxygen during storage should be minimized as much as possible to reduce the respiratory intensity of the food and the oxidation loss of the substrate, and to delay the ripening process. However, if the oxygen concentration is too low, it will, on the one hand, cause anaerobic respiration in the fruits and vegetables, leading to oxygen deficiency disorders; on the other hand, it will cause fermentation by anaerobic bacteria, such as Clostridium botulinum, etc. Since different fruits and vegetables have different critical oxygen concentrations, therefore, when using controlled atmosphere packaging, the amount of oxygen filled needs to be specially set according to the type of fruits and vegetables.

Analysis of Factors Affecting the Effect of Modified Atmosphere Packaging

The effects of modified atmosphere packaging are mainly reflected in three aspects: antibacterial effect; for fresh fruits and vegetables, it inhibits respiration and ripening; it maintains the original taste and shape of the food, especially for baked goods, reducing the unpleasant odor caused by lipid oxidation. From food packaging to transportation and storage, the effects of modified atmosphere packaging are restricted by many factors, including the selectivity of carbon dioxide for antibacterial action, the concentration of carbon dioxide, and the performance of modified atmosphere packaging materials.

The Selectivity of Carbon Dioxide in Inhibiting Bacteria and Its Impact on the Effect of Modified Atmosphere Packaging

According to the amount of oxygen required by microbial metabolism, they can be classified into aerobic microorganisms, facultative anaerobic microorganisms and anaerobic microorganisms.

Oxidative microorganisms are those whose normal growth requires an oxygen-rich environment. They include some aerobic bacteria and molds. For these microorganisms, a carbon dioxide concentration lower than 10% can inhibit their growth. The inhibitory effect of carbon dioxide on different genera of molds also varies. For example, Penicillium is more tolerant of carbon dioxide than Aspergillus.

Facultative anaerobic microorganisms refer to those that can survive in both aerobic and anaerobic environments. For example, yeast. When oxygen is scarce, these microorganisms survive by converting sugars into carbon dioxide and ethanol. Therefore, the inhibitory effect of carbon dioxide on them will be reduced.

Anaerobic microorganisms refer to those that grow better in an oxygen-free environment than in an oxygen-rich environment. For example, Clostridium sporogenes reproduces rapidly in an oxygen-free condition and can break down sugars, causing gas-producing deterioration and protein deterioration of food products such as fruits and vegetables. If such microorganisms exist, filling the packaging with a large amount of carbon dioxide will reduce the oxygen content in the packaging system, but this actually does not help to inhibit the growth of these microorganisms.