|
If produce is sealed in an insufficiently permeable film, undesirable anaerobic conditions (<1% O2 and >20% CO2) will develop with subsequent deterioration in quality. Conversely, if produce is sealed in a film with excessive permeability, little or no modified atmosphere will result and moisture loss will also lead to accelerated deterioration in quality. Use of MAPAX® gases and suitable packaging materials will solve these problems.
The key to successful modified atmosphere packaging (MAP) of fresh produce is to use a packaging film of correct intermediary permeability where a desirable equilibrium modified atmosphere (EMA) is established when the rate of oxygen and carbon dioxide transmission through the film equals the produce respiration rate. Typically, optimal EMAs of 3–10% O2 and 3–10% CO2 can dramatically increase the shelf life of fruits and vegetables. EMA is influenced by numerous factors such as respiration rate, temperature, packaging film, pack volume, fill weight and light. The respiration rate is affected by the variety, size, maturity and amount of produce preparation. Consequently, determination of the optimal EMA for a particular produce item is a complex problem that can only be solved through practical experimental testing.
Beneficial MAP of fresh produce can be attained by either sealing the produce in air or gas flushing with 3–10% O2 and 3–10% CO2 in 80 –90% N2. As previously explained, modified atmospheres evolve within an air-sealed pack because of produce respiration. However, in certain cases it may be desirable to gas flush so that a beneficial EMA is established more quickly. For example, enzymic browning of salad vegetables can be delayed by gas flushing instead of air packing. Practical experimental tests should be undertaken to confirm this. Different conditions may apply for peeled potatoes and apples, which should not be packed with oxygen because of enzymic reactions that bring about brown discoloration. Pre-peeled potatoes, for example, can be packed in 20% CO2 + 80% N2 with a prolonged shelf life from one half hour to 7–8 days at +38 to +42 °F.
Product | Lettuce | Mushrooms | Pre-peeled potatoes |
MAPAX Gas mixture | 3-10% CO2 and
3-10% O2 and
80-94% N2 | 3-10% CO2 and
3-10% O2 and
80-94% N2 | 40-60% CO2 and
40-60% N2 |
Gas volume per Product weight | 100-200 ml per 100 g prod. | 100-200 ml per 100 g prod. | 100-200 ml per 100 g prod. |
Typical shelf life | 2-5 days in air
5-10 days with MAP | 2-3 days in air
5-6 days with MAP | 0.5 hours in vacuum
2 days in air
10 days with MAP |
Typical material* | LDPE/OPP | LDPE/OPP | OPET/PVdC/PE-PVC/PE
PA/PE |
Typical machine | Deep-draw machine
Horizontal flow-pack | Deep-draw machine
Horizontal flow-pack | Deep-draw machine
Horizontal flow-pack |
Storage temp. | +38 to +42 oF | +38 to +42 oF | +38 to +42 oF |
*PVC is being replaced by APET or PS/EVOH, PVdC is being replaced by EVOH or OPA. |
