M.A.P. by Easy2Cook

Technology of Packaging Perishable Products in a Modified Atmosphere (MAP)

A brief Guide for Technologists

1. Description of Modified Atmosphere Packaging Technology

Modified Atmosphere Packaging (MAP) technology for food products emerged as an evolution of vacuum packaging technology. While vacuum packaging was a significant achievement in packaging technologies, it failed to solve several critical problems associated with storing perishable products in an airless environment.

Firstly, mechanical deformation of the product not only disrupts its texture but also, due to pressure from the multilayer barrier film material, leads to the release of moisture and juices. Consequently, the product loses part of its vitamin content, a liquid medium forms around it, promoting cell breakdown and aging. This is critical for juicy fresh meat products and fresh vegetables.

Secondly, the problem with vacuum is anaerobes and their harmful impact on many food groups. Anaerobes are organisms capable of living and developing in the absence of free oxygen. They include the causative agents of tetanus, gas gangrene, and some streptococci. If these microbes were present in the product before vacuum packaging, they begin to multiply intensively in the airless space. Although the vegetative forms of these microorganisms die in an oxygen environment, their spores are resistant and survive in a vacuum. Temperature fluctuations during storage can trigger their growth.

Botulism is an acute infectious-toxic disease caused by anaerobic bacteria and their toxins. Infection can occur through meat, fish, vegetable, and fruit preserves that have not been properly processed.

Thirdly, a problem with vacuum packaging is the change in the product's taste. The release of moisture inside the packaging leads to dehydration and alteration of taste properties.

The more progressive technology for extending shelf life — MAP — has found wide application in the food industry. Its first analogues were used as early as the beginning of the 1930s for transporting fruits and vegetables in a controlled gas atmosphere.

The essence of the atmosphere modification process in packaging involves replacing the air with a gas mixture, each component of which performs its own function:

- Nitrogen (N₂): An inert gas, used as a "diluent" and to displace oxygen. Allows for maximum removal of oxygen, limiting the development of aerobic bacteria.

- Carbon Dioxide (CO₂): Performs a bacteriostatic function, suppressing the growth of aerobic bacteria and mold. Easily dissolves in water and fats, increasing product acidity.

- Oxygen (O₂): On one hand, it causes oxidation and spoilage. On the other — it is necessary to preserve the bright red color of fresh meat (e.g., beef), associated with freshness. Its content in the mixture for meat can reach up to 80%.

A correctly selected gas mixture suppresses microorganism growth, preserves the taste, aroma, and appearance of the product, and significantly increases its shelf life without loss of quality. The optimal mixture depends on the specific product. For example, for fresh red meat, a mixture of 70-80% O₂ and 20-30% CO₂ is often used, while for ready-to-eat meals — 30% CO₂ and 70% N₂.

It is important to remember that MAP does not eliminate the need to store products at low temperatures (usually from -1°C to +5°C, depending on the product). The effectiveness of CO₂ increases with decreasing temperature. The product for packaging must be initially fresh and have a low microbiological load.

2. Packaging Materials for MAP

Packaging for MAP must meet strict requirements: complete airtightness, chemical inertness, environmental and food safety, high barrier properties (impermeability to oxygen, moisture, and the modified gas itself).

Historically, glass and tinplate were used as barrier materials. With the development of the polymer industry, plastic containers (trays) and films made from food-grade plastics have become widespread: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and its modifications.

A key element is multilayer barrier films for tray sealing, produced by co-extrusion. The outer layers provide strength and food safety, while the inner barrier layer (often made from ethylene vinyl alcohol copolymer, EVOH) protects against gas penetration. The reliability of the weld seam is critically important for preserving the gas environment.

Special reusable gastronorm containers made of food-grade stainless steel with airtight lids are also used in MAP, which is especially convenient for restaurants and kitchens.

3. Equipment for MAP

Equipment is divided into several main types:

1. Tray Sealers: Automatic or semi-automatic machines that place the product tray in a sealed chamber, evacuate the air, inject a specified gas mixture, and seal the tray with a barrier film.

2. Thermoforming Machines with MAP Function: Integrated lines that form a tray from a roll of barrier plastic, fill it with product, vacuum it, fill it with gas, and seal it with film, after which the finished package is die-cut.

3. Systems for Packaging in Gastronorm Containers: Specialized equipment that evacuates and fills reusable steel containers with gas, often equipped with a control system and label printer.

4. Machines for Packaging in Vacuum Bags with Gas: Used for large-sized products. A fitting is inserted into the bag with the product, through which air is evacuated and the gas mixture is injected, after which the bag is sealed.

(General guidelines. Exact mixture compositions are determined for each specific product through laboratory testing.)

- Raw Red Meat (beef, lamb): Retail packaging: 70-80% O₂, 20-30% CO₂. Bulk packaging: 65% O₂, 35% CO₂. Shelf life in MAP: 5-8 days (at 0…+2°C).

- Fresh Poultry (chicken, turkey): Retail packaging: 30% CO₂, 70% N₂. Bulk packaging (whole carcasses): 100% CO₂. Shelf life in MAP: 10-21 days.

- Raw Fish (lean, white): Retail packaging: 30% O₂, 40% CO₂, 30% N₂. Shelf life in MAP: 4-6 days.

- Raw Fish (oily): Retail packaging: 40% CO₂, 60% N₂. Shelf life in MAP: 4-6 days.

- Ready-to-Eat Meat Products (sausages, ham): Retail packaging: 30% CO₂, 70% N₂. Shelf life in MAP: 3-7 weeks.

- Ready-to-Eat Meals and Salads: Retail packaging: 30% CO₂, 70% N₂. Shelf life in MAP: 3-7 weeks.

- Fresh Pasta: Retail packaging: 50% CO₂, 50% N₂. Shelf life in MAP: 3-4 weeks.

- Bakery Products: Retail packaging: 50% CO₂, 50% N₂ (except for cream-filled products: 100% N₂). Shelf life in MAP: 4-12 weeks.

- Hard Cheeses: Retail packaging: 100% CO₂.

- Fresh Cut Vegetables and Fruits: Retail packaging: 5% O₂, 5% CO₂, 90% N₂. Shelf life in MAP: 5-35 days.

Important: All data provided is for reference only. Developing the optimal gas mixture and determining precise shelf life for a specific product requires conducting microbiological and chemical studies in specialized laboratories.

For consultation on equipment selection and the development of individual MAP solutions for your products, we recommend contacting the experts at Easy2Cook..