Because fruit and vegetables respire, the biggest success factor in packaging is permeability. If fruit and vegetables are sealed in a film which is not sufficiently permeable, undesirable anaerobic conditions (<1% oxygen and >20% carbon dioxide) will ensue. This will result in deterioration of the quality. Conversely, if produce is sealed in a film with excessive permeability, the modified atmosphere will not be retained and moisture loss will also lead to accelerated deterioration in quality. Examples of suitable Modified Atmosphere Packaging (MAP) films for fresh fruit and vegetables include microporous film or LDPE/OPP.
When fruit and vegetables respire, the modified atmosphere evolves into an equilibrium modified atmosphere (EMA). With an EMA, the rate of oxygen (O2) and carbon dioxide (CO2) transmission through the film equals the respiration rate of the produce. The EMA is influenced by numerous factors such as respiration rate, temperature, packaging film, pack volume, fill weight and light. The respiration rate, in turn, is affected by the variety, size, maturity and preparation of the produce. Consequently, working out the optimal EMA for a particular item is a complex equation.
At Linde, we can help you select the gas mixture that accommodates different respiration rates to create the optimum EMA for your produce. Typically, optimal EMAs of 3–10% O2 and 3–10% CO2 can dramatically increase the shelf life of fruit and vegetables.
As previously explained, modified atmospheres evolve within an air-sealed pack due to respiration. However, in certain cases it may be desirable to gas-flush the package to accelerate establishment of a beneficial EMA. For example, enzymatic browning of salad vegetables can be delayed by gas flushing instead of air packing.
Our engineers will run a series of tests to establish the optimum solution for your fruit or vegetables. Different conditions may apply, for example, to peeled potatoes and apples (which should not be packed with oxygen to avoid enzymatic reactions that result in browning). Pre-peeled potatoes, for example, can be packed in 20% CO2 + 80% N2. This extends the shelf life from 0.5 hours to 7–8 days at +4 to +5°C (+39.2 to +41ºF).
