2. Consider the Respiration Rate of the Fruit

Different fruits have different respiration rates, so the gas exchange design should be based on the specific respiration rate of the fruit. Fruits with higher respiration rates require higher gas exchange rates.

3. Select Appropriate Packaging Materials

The permeability of the packaging material to gases needs to match the respiration rate of the fruit. Common packaging materials include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET).

4. Design Thickness and Perforations of Packaging Materials

The thickness of the packaging material and whether it has perforations will affect the gas exchange rate. Thinner materials or packaging with small perforations can increase the gas exchange rate.

5. Packaging Conditions

The temperature and humidity inside the packaging also affect gas exchange and the preservation effect of the fruits. It is necessary to control the temperature (usually 0-5°C) and humidity (above 85%) of the packaging and storage environment.

Specific Design Steps

1.Measure the Respiration Rate of the Fruit: Measure the oxygen consumption rate and carbon dioxide production rate of the fruit at different temperatures.

2.Select Packaging Materials: Choose appropriate packaging materials based on the fruit's respiration rate.

3.Design Thickness and Perforations of Packaging Materials: Calculate the required gas permeability and choose appropriate material thickness and perforation options.

4.Test and Adjust: Conduct packaging trials and adjust the gas composition, materials, and packaging conditions based on actual results.

Example

Suppose we need to package strawberries, which have a respiration rate at 5°C of:

Oxygen consumption rate: 10 ml/kg·h
Carbon dioxide production rate: 9 ml/kg·h

The chosen packaging material is polyethylene (PE), which has gas permeability at 5°C of:

Oxygen: 5000 ml/m²·24h·atm
Carbon dioxide: 2500 ml/m²·24h·atm

By calculating the required packaging area and thickness, we can maintain the desired concentrations of oxygen and carbon dioxide inside the packaging.

Conclusion

Modified atmosphere packaging for fresh fruits requires comprehensive consideration of the fruits' respiration characteristics, the gas permeability of the packaging materials, and the control of the packaging environment. Through rational design and adjustment, the shelf life of the fruits can be effectively extended.