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Fruit and vegetables are products that ‘breathe’. A decisive factor in the successful packaging of fruit and vegetables is therefore the permeability of the packaging material. Packing them in film cover with excessively low level of permeability causes a undesired anaerobic atmosphere (<1% oxygen and >20% carbon dioxide). This quickly reduces the quality. When these products are packed with film with an excessively high grade of permeability, the protective atmosphere cannot be maintained. The quality can also be compromised due to loss of moist. Examples of suitable film covers for packing fresh fruit and vegetables within a protective atmosphere are microporous film and LDPE/OPP.
As potatoes, fruit and vegetable breathe, the protective atmosphere in combination with the correct film creates a balanced atmosphere (equilibrium modified atmosphere packaging, EMAP). In the event of an EMAP, the foil passes as much oxygen and carbon dioxide as breathed in and out by the potatoes, fruit and vegetables. An EMAP depends on many actors:
- the extent to which a products breathes
- the temperature
- the type of film
- the packaging volume
- the net weight
- the amount of light the products is exposed to.
Linde helps you selecting the gas mixtures that are adjusted to the level of breathing of the different types of fruit and vegetables. With an effective EMAP of 3–10% O2 and 3–10% CO2, you can usually achieve a considerable improvement in shelf life.
As explained above, MAP atmospheres develop into an EMAP as a result of the fruit and vegetables breathing. However, in some cases it can be desirable to rinse the packaging with a certain type of gas mixture in order to accelerate the formation of the desired EMAP. The enzymatic brown of vegetables for salads can e.g. be inhibited by rinsing with gas.
Your Linde advisor can take a series of samples to establish the best possible packaging method for you fruit and vegetables. The solution depends on the type and the pretreatment. Peeled potatoes and apples, for example, must not be packed with oxygen in order to prevent them from turning brown due to enzymatic reactions. Peeled potatoes are best packed in a mixture of 20% CO2 and 80% N2. In temperatures of 4 to 5°C, this prolongs shelf life from half an hour to 7 or 8 days.