Four key elements of using food modified atmosphere packaging technology

The modified atmosphere packaging technology of food first appeared in the European food industry, and then it was introduced into the Americas and Japan. It has been widely used by countries in the world. At present, the use of modified atmosphere packaging technology in the food industry in our country is not common, and how to carry out modified atmosphere packaging is an important issue for packaging workers in urgent need of research and solution.

In the past, in order to extend the shelf life of foods, people mainly used heating, salt leaching, smoking and the addition of preservatives, disinfectants, antioxidants and other means to pretreat foods. These methods have more or less some influence on foods. With the gradual improvement of people's quality of life, people began to look for other food preservation methods, and modified atmosphere packaging is one of them.

Modified atmosphere packaging adopts packaging materials with gas barrier properties to package foods, and a certain proportion of mixed gas is filled into the packaging to prevent foods from falling in quality in physics, chemistry, biology, etc., or slowing the decline of quality. There can be a relatively long shelf life. The change of food during transportation and storage is very complicated. The type and quality of food, microbiological environment, and storage temperature all affect the change of food quality. Modified atmosphere packaging is a technology that integrates multiple disciplines such as physics, chemistry, and biology.

Because of the different physiological characteristics of food products and the conditions encountered in food distribution and marketing, the requirements for packaging vary greatly. There are many factors to consider when using food modified atmosphere packaging technology. These include the following four major factors: Elements.

First, the proper proportion of gas mixture

The most commonly used modified atmosphere packaging is nitrogen, carbon dioxide, oxygen three gases or their mixed gas. Nitrogen is stable in nature, and the use of nitrogen is generally used to exclude oxygen, thereby slowing the oxidation and respiration of foods. Nitrogen also has a certain inhibitory effect on the growth of bacteria. In addition, nitrogen is basically insoluble in water and grease. The adsorption of nitrogen on food is very small, and the phenomenon of gradual shrinkage is not caused by gas absorption during packaging.

Carbon dioxide is the most critical gas in modified atmosphere packaging. It can inhibit the growth of bacteria and fungi. When used in the packaging of fruits and vegetables, carbon dioxide has the function of strengthening oxygen and reducing respiratory intensity. However, when using carbon dioxide, care must be taken that carbon dioxide has a high solubility in water and grease, and the formation of carbonic acid after dissolution will change the pH and taste of the food. At the same time, when the carbon dioxide is dissolved, the amount of gas in the package will decrease, and the food packaging will shrink easily. Not full, affecting the appearance of food. The use of carbon dioxide in modified atmosphere packaging must take into consideration various factors such as storage temperature, food moisture, and the type and quantity of microorganisms.

Modified atmosphere packaging generally uses oxygen only in the following three situations: 1) Maintaining the color of the food with oxygen, such as the red color of the meat. 2) Maintain the respiration of fruits and vegetables. 3) Inhibition of anaerobic microbial growth.

Second, the gas barrier

Gas barrier film is the most important part of modified atmosphere packaging. It must have high gas barrier performance to ensure that the mixed gas inside the package does not leak. In addition, for fruits and vegetables, due to their respiration will change the proportion of mixed gas, in this case also must be to achieve a dynamic balance of the gas mixture, the use of barrier gas permeability to maintain the ideal ratio of mixed gas. Air-conditioning packaging requires very strict permeability to packaging materials. In addition, the thermoformability of the film and the reliability of the seal must also be considered. At present, the commonly used films are: polyester (PET), polypropylene (PP), polystyrene (PS), polyvinylidene chloride (PVDC), ethylene-vinyl acetate (EVA), ethylene-vinyl alcohol ( EVOH) and various composite films, metallized films.

Third, the storage temperature

Storage temperature is an important link that affects the shelf life of foods. Under low temperature conditions, the oxidation rate and the respiratory rate of foods will be weakened, and the growth of microorganisms will be inhibited. Even below a certain temperature limit, microbial activity will stop completely. Most of the microorganisms that cause food spoilage are mesophilic microorganisms. Take Escherichia coli as an example. The minimum growth temperature is 10°C, and the most suitable temperature for growth is 37°C. Therefore, it is generally stored by freezing and refrigerating methods. food.

But on the other hand, low temperatures also have different degrees of influence on certain foods. The specific temperature storage should be determined according to the food it packages. In general, the frozen fish is frozen, and the fruits and vegetables are stored by refrigeration.

Fourth, food quality and microbiological environment

Food molds and spoilage are mainly caused by molds, bacteria, and other microorganisms. Therefore, the type and quantity of microorganisms attached to foods and surfaces before packaging are also an important factor affecting the shelf life of foods, especially for foods with higher water activity. The growth of microorganisms is not only affected by temperature, but also related to the water activity of foods. Bacteria were unable to reproduce in foods having a water activity below 0.90. The minimum water activity value of the yeast was 0.88, and the mold was 0.80. The water activity value of fish, fruits and other foods is as high as 0.98, which is very suitable for the propagation and growth of microorganisms. It is very important for the sterilization of such foods before packaging.

In addition to the microbial environment, the quality of food before packaging is very important. For example, how ripe the fruits picked and whether there are mechanical damages directly affect the respiration intensity and antibacterial performance of foods and thus affect the concentration of oxygen and carbon dioxide in the packaging. When using modified atmosphere packaging technology, the quality of food before packaging is An element that must be considered.

The four major elements of food atmosphere packaging are linked and indispensable. Their joint action determines the length of the food shelf life. Of course, due to the differences in the packaged food, the requirements for each element are also different.