How to choose sealing film in MAP modified atmosphere packaging
The choice of sealing film is very important in modified atmosphere packaging. Different food products have different requirements for packaging film. For example, cooked food and fresh food industries need high barrier film materials. For vegetables and fruits, they need high permeability packaging materials. Because each kind of food has different requirements for packaging film, so when choosing packaging film materials in modified atmosphere packaging, it is necessary to select suitable film materials according to the characteristics of food materials, otherwise the effect of modified atmosphere packaging will be greatly reduced.
Packaging film selection for cooked ready to eat food in modified atmosphere packaging
For the packaging film of cooked food, the main reason for choosing high barrier film material is that the modified atmosphere packaging of cooked food mainly prevents oxidation of products by isolating oxygen, and prolongs the shelf life. Now the film belongs to multi-layer supply film, which has a certain oxygen permeability, if oxygen permeability. When food is stored for a period of time, the oxygen concentration in the packaging box will rise due to gas exchange with air, which will affect the shelf life of food.
We take ordinary nylon film as an example, usually in 200*140*35 boxes, the residual oxygen in the box is about 1-2% after 4-5 days. Right, the residual oxygen content of different PP films ranges from 2% to 3%, while the residual oxygen content of high barrier nylon films remains at about 0.5%. For the delicatessen industry, the lower the residual oxygen content (under the same conditions) the longer the fresh-keeping period. Therefore, in the modified atmosphere packaging of delicatessen, it is better to choose high barrier film materials. Generally, the better the high barrier nylon film materials are. The 24-hour oxygen permeability OTR of the diaphragm is less than 5cc/(23 C), which is realized by compounding an EVOH isolation layer in the packaging film. It is mainly used for cooked food with high freshness requirement and long time.
However, in order to save the cost of cooked food, the oxygen permeability OTR should be at least less than 30-30 cc/(23 C), and the membrane with less than 10 days’fresh-keeping time is not recommended. Here, we should also emphasize that the shelf life of food is not only determined by high barrier film material. Packaging material is only an important part of the factors that effect packaging quality, including packaging machine quality, packages’ storage environment.
Packaging film selection for fruits and vegetables in modified atmosphere packaging
For fruits and vegetables, the choice of modified atmosphere packaging film is very different from that of cooked food industry. Because fruits and vegetables need breathing, when choosing packaging materials, most of them need to choose high permeability film materials, such as ordinary PP and PE. This film has better air permeability, and can better exchange gas with the external environment to make the bag. If the high barrier packaging material is chosen, because there is no way to exchange the atmosphere with the outside, the fermentation of food materials will occur in the anoxic environment, which will be more disadvantageous to the fresh-keeping packaging of fruits and vegetables. The principle of modified atmosphere packaging of fruits and vegetables is different from that of fresh and cooked food, and the requirements for film are also different. On the contrary, it requires a certain permeability of the membrane, which can dynamically supplement the low concentration of oxygen needed for dormancy of fruits and vegetables. The principle of modified atmosphere packaging for fruits and vegetables is to replace the air in packaging boxes or bags by using modified atmosphere fresh-keeping gases (2-4 kinds of gases are mixed according to the characteristics of food), change the external environment of food in boxes (bags), inhibit the growth and reproduction of bacteria (microorganisms), slow down the metabolism of fresh fruits and vegetables, and prolong the shelf life or shelf of food. Period. Take fresh fruits and vegetables as an example: fresh fruits and vegetables are still breathing after harvesting, consuming CO2 to produce CO2, gradually increasing the content of CO2 in the environment and reducing the concentration of O2. High permeability plastic film can exchange gas with the atmosphere to supplement the consumption of CO2 and discharge CO2. When the permeation rate of gas to the film is equal to the respiration rate of fruits and vegetables, the gas in the packaging bag reaches a certain equilibrium concentration, which can maintain a weak respiration rate without anaerobic respiration, and delay the ripening of fruits and vegetables to fresh-keeping. Modified atmosphere packaging can ensure food taste, nutritional composition and fresh-keeping period without using preservatives and additives. Therefore, for the modified atmosphere packaging of fruits and vegetables, we need to choose the film material with high permeability. Of course, for different food materials, the breathing rate is different, storage and sale problems are also different. This in the selection of film, we need to adjust according to the different food materials, in general, for the fruit. Modified atmosphere packaging of vegetables, film permeability is required.