How to choose sealing film in MAP modified atmosphere packaging?
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 of 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 affect 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.
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. Unlike fresh and cooked foods, fruits and vegetables require 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 neutral gases such as nitrogen and carbon dioxide, 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 food. Take fresh fruits and vegetables as an example: fresh fruits and vegetables are still breathing after harvesting, living plant texture cause to produce carbon dioxide which diffuse from the packaging.
So it will increase carbon dioxide in the environment gradually and will decrease oxygen concentration.
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.
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