Packaging material has a direct and significant influence on the effectiveness of Modified Atmosphere Packaging (MAP). The choice of the right material largely determines how well gases such as nitrogen remain within the packaging and how effectively unwanted gases are excluded. Materials with the appropriate gas permeability, mechanical strength, and barrier properties are essential for maintaining the optimal gas composition that extends product shelf life. An incorrect material choice can lead to rapid quality deterioration due to insufficient protection against gas exchange.
What is Modified Atmosphere Packaging (MAP) and why is it important?
Modified Atmosphere Packaging (MAP) is a packaging technique where the natural air composition within a package is modified to extend the shelf life of products. With this method, the normal atmosphere (approximately 78% nitrogen, 21% oxygen, and 1% other gases) is replaced by a carefully composed mix of gases, often with an increased content of nitrogen and carbon dioxide and a reduced oxygen content.
MAP is important because it significantly slows down the natural aging processes of products. By reducing the oxygen content, oxidation and the growth of aerobic microorganisms are inhibited. At the same time, an increased carbon dioxide content can counteract the growth of certain bacteria, while nitrogen functions as an inert filler gas that displaces oxygen and stabilizes the packaging.
This technique is widely applied in various industries, including:
- Food industry for meat and produce preservation (for meat, fish, vegetables, fruit, and bakery products)
- Pharmaceutical sector
- Electronics (protection against oxidation)
- Metalworking
However, the effectiveness of MAP strongly depends on the chosen packaging material, which must be able to maintain the modified atmosphere throughout the desired shelf life period.
Which properties of packaging material influence MAP effectiveness?
The effectiveness of MAP is determined by several critical properties of the packaging material. Gas permeability is the most determining factor, but other properties also play an important role in the success of MAP applications.
The most important properties are:
- Gas permeability: The extent to which the material allows gases such as oxygen, carbon dioxide, and nitrogen to pass through. This property is measured as transmission rate and determines how well the modified atmosphere is maintained.
- Moisture barrier: The ability to prevent water vapor, which is important for maintaining product quality and preventing condensation.
- Mechanical strength: The resistance against tears, perforations, and impact during transport and handling, which is crucial for preserving the integrity of the MAP.
- Thermal stability: The ability to maintain properties at different temperatures, especially important for products that are refrigerated, frozen, or heated.
- Sealability: The ability to form hermetic seals, which is essential for maintaining the gas composition.
- Chemical resistance: Resistance against interaction with the packaged product and the gases in the packaging.
These properties must be balanced and aligned with the specific product, the desired shelf life, and the environmental conditions to which the packaging is exposed.
How does the gas permeability of packaging influence the MAP result?
The gas permeability of packaging material has a direct and decisive influence on the MAP result. This property determines how quickly gases can diffuse through the material, which directly affects how long the desired atmosphere within the packaging remains intact.
For different gases, specific permeability measurements are used:
- OTR (Oxygen Transmission Rate): Measures how much oxygen can penetrate the material within a certain time, surface area, and pressure. A low OTR is usually desired for MAP applications to prevent oxidation.
- CTR (Carbon Dioxide Transmission Rate): Measures the permeability for carbon dioxide. This is important when CO₂ is used as a protective gas in the packaging.
- NVTR (Nitrogen Vapor Transmission Rate): Measures the permeability for nitrogen, which is important when nitrogen is used as the primary filler gas.
Gas permeability influences MAP results in various ways:
- Too high permeability: The protective gases escape too quickly and external gases (such as oxygen) penetrate too easily, shortening shelf life.
- Too low permeability: For some fresh products that still respire (such as vegetables and fruits), a completely impermeable packaging can lead to anaerobic conditions that accelerate spoilage.
- Selective permeability: Some materials allow certain gases to pass through more easily than others, which can be utilized for products with specific needs.
The ideal gas permeability depends on the product. For non-respiring products such as meat and cheese, materials with very low permeability are optimal, while for fresh vegetables and fruits, a controlled, selective permeability is often better.
Which packaging materials are most suitable for MAP applications?
For MAP applications, various packaging materials are available, each with their own properties that make them more or less suitable for specific products. The choice depends on the required barrier properties, product characteristics, and desired shelf life.
| Material Type | Gas Permeability | Advantages | Suitable Applications |
|---|---|---|---|
| Polyethylene (PE) | Moderate to high | Flexible, good sealability, inexpensive | Respiring products, shorter shelf life |
| Polypropylene (PP) | Moderate | Good moisture resistance, heat resistant | Products that can be heated |
| Polyethylene terephthalate (PET) | Low to moderate | Transparent, strong, recyclable | Beverages, sauces, processed foods |
| Polyvinyl chloride (PVC) | Low to moderate | Good barrier, transparent | Meat, cheese, medical products |
| Polyamide (PA/Nylon) | Very low | Excellent gas barrier, strong | Meat, cheese, products with long shelf life |
| Ethylene vinyl alcohol (EVOH) | Extremely low | Superior oxygen barrier | Primarily used in multilayer films |
| Multilayer films | Customizable | Combines advantages of different materials | Widely applicable, can be adapted to specific products |
Multilayer films or laminates are particularly popular for MAP applications because they combine the strong properties of different materials. A typical multilayer structure might consist of:
- Outer layer: PET for strength and protection
- Middle layer: EVOH or PA for gas barrier
- Inner layer: PE or PP for sealing and product contact
This combination offers optimal protection against gas exchange while keeping the packaging practical and cost-effective.
How do you choose the right packaging material for your MAP process?
Selecting the right packaging material for your MAP process requires a systematic approach that takes multiple factors into account. Begin by analyzing the specific properties of your product and the food safety requirements.
Follow these steps for a well-considered choice:
- Analyze your product:
- Respiration rate (for fresh products)
- Sensitivity to oxygen, moisture, and light
- Desired shelf life
- Physical characteristics (shape, weight, sharp edges)
- Determine the optimal gas composition:
- Which gases are needed for your product?
- Which ratios are optimal?
- Evaluate environmental factors:
- Temperature conditions during storage and transport
- Humidity
- Possible mechanical stress
- Test different materials:
- Conduct shelf life tests with different material options
- Measure gas retention over time
- Evaluate product quality
For products that require a very long shelf life, such as certain meats or cheeses, materials with very low gas permeability such as multilayer films with EVOH or metal-coated films are ideal. For fresh vegetables and fruits, materials with controlled permeability, such as micro-perforated PE or special breathable films, may give better results.
In making your choice, also consider practical aspects such as machine processing, sealing behavior, transparency (if desired), and costs. The right balance between performance and cost-effectiveness is essential for a successful MAP process.
What are the key conclusions about packaging material and MAP effectiveness?
The relationship between packaging material and MAP effectiveness is complex but crucial for the success of your packaging strategy. The key conclusions you should remember are:
- The gas permeability of the packaging material is the most critical property that directly influences how long the protective atmosphere is maintained.
- There is no universally ideal packaging material for all MAP applications. The right choice always depends on the specific product and the desired shelf life.
- Multilayer films usually offer the best performance by combining the strong properties of different materials.
- For respiring products, a controlled, selective permeability is often better than an absolute barrier.
- Besides gas permeability, mechanical properties, sealability, and moisture barrier are also important factors in material selection.
- Systematic testing is essential to determine the optimal combination of material and gas composition.
Technological developments in packaging materials continue, with new innovations such as active and intelligent packaging that can further improve the effectiveness of MAP. These advanced materials can, for example, absorb excess moisture, remove ethylene, or even actively regulate the gas composition.
At Presscon, we understand the importance of the right combination of gas composition and packaging material. Our nitrogen generators deliver nitrogen of consistent quality for MAP applications, ensuring you have a reliable gas source that works perfectly with your carefully chosen packaging materials. By investing in both the right materials and a reliable nitrogen supply, you can maximize the shelf life of your products and ensure quality. Contact our MAP packaging specialists today for expert advice on your specific application.
