Controlled atmosphere packaging (CAP) operates on the principle of modifying the gaseous environment inside a package to extend the shelf life of its contents, primarily food, by slowing down natural degradation processes. According to Larsen & Watkins (1995), this is typically achieved by reducing oxygen (O2) levels and/or increasing carbon dioxide (CO2) levels.
How Does CAP Work?
The core principle of CAP involves creating an atmosphere distinct from the normal air surrounding us. This is usually done by:
- Lowering Oxygen Levels: Oxygen is a key reactant in many spoilage processes, including:
- Respiration of fresh produce, where oxygen is consumed and carbon dioxide is produced, leading to ripening and deterioration.
- Oxidative browning and discoloration.
- Growth of many aerobic microorganisms that cause spoilage.
- Increasing Carbon Dioxide Levels: CO2 acts as an inhibitor, slowing down:
- The respiration rate of produce, extending its fresh life.
- The growth of many spoilage microorganisms.
Table of Typical Gas Composition in CAP
| Gas | Normal Atmosphere | Typical CAP (for Produce) |
|---|---|---|
| Oxygen (O2) | ~21% | 3-10% |
| Carbon Dioxide (CO2) | ~0.04% | 3-10% |
| Nitrogen (N2) | ~78% | Balance |
Impact on Food Preservation
By altering the atmospheric composition, CAP achieves several benefits:
- Reduced Respiration Rate: Slowing down the metabolic rate of fresh produce helps delay ripening and senescence (aging).
- This leads to less water loss, maintaining the produce’s turgidity.
- It helps keep the nutritional value intact for longer.
- Inhibited Microbial Growth:
- Lowering O2 limits the growth of aerobic bacteria and molds, the most common spoilage agents in many food types.
- Higher CO2 concentrations create an environment less conducive to bacterial and mold multiplication.
- Delayed Enzymatic Reactions: Many enzymatic reactions responsible for quality degradation, such as browning, are slowed by the modified atmosphere.
Practical Considerations
- Material Selection: Packaging materials must be selected carefully based on their gas permeability to maintain the desired atmosphere inside.
- Initial Flushing: Packages are usually flushed with the modified gas mixture before sealing.
- Continuous Monitoring: While not required for all applications, in certain cases continuous monitoring of gas composition might be needed to ensure the integrity of the modified atmosphere.
Conclusion
Controlled atmosphere packaging is a preservation method that manipulates the air inside food packages to slow down the processes of spoilage, respiration, and microbial growth. By carefully controlling the levels of oxygen and carbon dioxide, CAP can extend the shelf life and maintain the quality of perishable goods, particularly fresh produce. The reference (Larsen & Watkins, 1995) states that CAP utilizes a low O2 and/or high CO2 atmosphere to achieve this objective.
