Packaging principle and packaging materials of modified atmosphere packaging

Packaging principle and packaging materials of modified atmosphere packaging

The packaging principle of the modified atmosphere packaging machine is to use the modified atmosphere preservation gas (2-4 kinds of gases are mixed according to the characteristics of the food) to replace the air in the packaging box or packaging bag, change the external environment of the food in the box (bag), and inhibit bacteria. The growth and reproduction of (microorganisms) slow down the metabolism of fresh fruits and vegetables, thereby prolonging the preservation period or shelf life of food. Take the preservation of fruits and vegetables as an example: fresh fruits and vegetables still undergo respiration after picking, consuming oxygen to generate carbon dioxide, gradually increasing the carbon dioxide content in the environment and reducing the oxygen concentration. consumes oxygen and expels carbon dioxide. When the speed of gas penetration into the film is equal to the respiration speed of fruits and vegetables, the gas in the packaging bag reaches a certain equilibrium concentration, which can make the fruits and vegetables maintain a weak respiration rate without anaerobic respiration, thereby delaying the ripening of fruits and vegetables and keeping them fresh. The use of modified atmosphere packaging can ensure the taste, nutritional content and fresh-keeping period of food without using preservatives and additives.

There are many ways to keep food fresh, and the modified atmosphere packaging machine is one of the advanced methods. The so-called modified atmosphere means that the food is placed in a certain proportion of ideal mixed gas to prolong the biochemical deterioration of life. At present, fresh fruits and vegetables, clean vegetables, cut vegetables, and food products in major supermarkets in Europe and the United States have spread all over the shelves under the condition of cold chain circulation. Development is important, which is not only a new subject of food engineering, but also an inevitable law of historical development.

Modified atmosphere fresh-keeping packaging machine, collectively referred to as map packaging internationally, the modified atmosphere fresh-keeping gas machine used 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; maintain the color of fresh meat, maintain the oxygen-rich respiration and freshness of fresh fruits and vegetables; n2 is used as filling gas. The composition ratio of the composite gas is properly selected according to the type of food, preservation requirements and packaging materials to achieve the effect of high preservation quality of the packaged food, good preservation of nutrients, truly achieving the original properties and delaying the shelf life of preservation.

The so-called food preservation is to maintain the original fresh state of the food. For cooked food, it is about keeping the cooked food fresh on the day it was made. Traditional packaging and storage can only solve the problem of food quality, but cannot keep food fresh. Due to the problem of the preservation period, many real specialty food stores cannot go out of their homes and cannot be sold overnight, and the market radius is very narrow, thus losing a huge consumer group. The modified atmosphere fresh-keeping packaging machine solves the problem of food preservation to a large extent, and can extend the fresh-keeping period of cooked food from 1 day to more than 7 days, which greatly expands the market radius of manufacturers, and also enables consumers to taste at home. Local specialty foods that are thousands of miles apart have made a better balance between freshness and safety period for consumers.

Cakes without cream can be kept fresh for 20-30 days at room temperature, and moon cakes and pudding cakes can be kept fresh for 60-90 days at room temperature with high-barrier composite film. Soy products and cooked meat products of livestock and poultry can be filled with co2 and n2, which can effectively inhibit the reproduction of coliform bacteria. Keep fresh for 5-12 days at room temperature of 20℃-25℃, keep fresh for about 30 days at room temperature after conditioning and sterilization at 85℃-90℃, and keep fresh for 60-90 days at 0℃-4℃ refrigerated temperature.

What are the factors that affect the effect of modified atmosphere packaging

1. Characteristics of food

Such as water activity, pH value will determine which microorganisms grow on the product.

2. Handling and processing of food

Food processing must be carried out at low temperatures and contact with air, equipment and personnel must be minimized.

3. Type and quantity of microorganisms

The number of colonies in food is very important, which is related to the shelf life.

4. Hygiene level

Follow good hygiene regulations and maintain high hygiene standards throughout the processing chain to inhibit bacterial growth.

5. Temperature

Temperature is a key factor affecting product shelf life and freshness safety. If refrigerated food is not processed and stored at a suitable temperature, it is easy to cause the growth of microorganisms to accelerate and cause food spoilage.

6. Packaging machinery

The forming, sealing and vacuuming systems of packaging equipment must be reliable and have good sealing performance. To maintain cleanliness, equipment must be completely washable.

7. Characteristics of packaging materials

Packaging materials need to be able to extend the shelf life of the product and ensure that the product has a good display effect.

8. The volume of gas in the package

Fill the package with an appropriate volume of gas to achieve a more beautiful display effect.

9. Mixed gas

The type of gas used and the proportion of ingredients are closely related to the shelf life and appearance of the product.

How to choose the right modified atmosphere packaging material

Undoubtedly, in order to carry out modified atmosphere packaging of products, it is necessary to make a reasonable choice of the air permeability of packaging materials according to the characteristics of the products. Generally, the gas used for modified atmosphere packaging is a mixed gas of O2, CO2 and N2, or a mixed gas of O2 and CO2. Therefore, when selecting a modified atmosphere packaging material, the O2 permeability, CO2 permeability, N2 permeability of the material must be checked. When conducting an accurate test of permeability, it is absolutely impossible to test various gases over the other, or to only test the O2 transmittance of the material and then convert it according to the empirical ratio, and a comprehensive test must be carried out. It is conceivable that if the selection of modified atmosphere packaging materials is wrong due to incorrect index detection or lack of comprehensive inspection, it will not only cause huge economic losses to the enterprise, but also cause serious waste of resources.

At present, there are two types of air permeability test methods commonly used in the world: differential pressure method and equal pressure method. On the whole, the test object of the isobaric method equipment is very simple. At present, it can only detect the O2 permeability or CO2 permeability of the material. So far, no company can provide the isobaric method equipment for testing the N2 permeability. For the differential pressure method equipment, it is completely different, because this method itself has no selectivity to the test gas, and can test conventional gases such as O2, N2, CO2, etc., the test cost is low, and the test environment can be automatically controlled. In addition, due to the support of membrane technology theory, the vacuum differential pressure method can not only detect the permeability of various common gases to the sample, but also give the diffusion coefficient and solubility coefficient of the test gas to the sample at the same time. Compared with the equal pressure method equipment, the differential pressure method air permeability test equipment is more suitable for the research institutions of modified atmosphere packaging materials and the manufacturers to conduct comprehensive testing and comprehensive analysis of the materials.

Permeability of different gases to materials

The design of the modified atmosphere packaging machine system should consider many factors, among which the more important factor is the relative content of CO2 and O2 in the package, which is mainly determined by the gas concentration in the package and the permeability of the packaging material, that is, the modified atmosphere preservation gas Proportional control accuracy and gas replacement rate of packaging materials. Different from vacuum packaging or nitrogen-filled packaging, the materials of modified atmosphere packaging machines are mostly low-barrier materials, which have greater gas permeability. The structure is related to factors such as the diffusivity and solubility of the gas, and the influence of additives. However, different gases have different permeability to the same material. For the same material, the permeability of N2 is generally very small, O2 is slightly larger, and CO2 is larger. This is related to the size of gas molecules and the size of the gas. the shape of the molecule. The smaller the dynamic diameter of the molecule, the easier the diffusion in the polymer and the larger the diffusion coefficient. But the size of the gas molecular diameter is not the factor that determines the permeability, because the permeability is also related to the solubility of the gas in the polymer. In addition, the shape of the molecule can also affect the permeability. Some studies have shown that the diffusion ability and permeability of the elongated molecule are strong, and the small change of the molecular shape will cause a great change in the permeability.

Because of the longer shelf life, manufacturers and retailers can arrange production/distribution/sales more rationally, reduce production costs, reduce return losses, reduce distribution costs, expand sales, and increase profitability. For retailers, fresh Meat retail packaging is the trend. This is mainly determined by two aspects: First, consumers are paying more and more attention to food safety, and the consumption of fresh meat in urban markets is becoming more and more saturated. The convenient modified atmosphere packaging machine has become the development direction of fresh meat retail packaging, and the development experience of the same foreign industry also shows this trend; second, for the supermarket itself, the implementation of the food safety law and the continuous increase in labor costs are promoting supermarkets. Meat suppliers seeking safe packaging that can be used for direct sales can achieve economies of scale through centralized production and unified distribution, and achieve the goal of saving costs, reducing food safety risks, and increasing revenue.