Modified Atmosphere Packaging (MAP) Trays & Barrier Films Guide

On this pageHow MAP Works Common Gas Mixes Barrier: The Number That Matters Choosing the Tray Choosing the Lidding Film Seal Integrity Is Everything Shelf-Life Trials Compliance and Documentation Specification Checklist Buyer FAQ

Fresh meat, fish, poultry, ready meals and sliced produce all lose quality for two main reasons: oxygen drives spoilage and discolouration, and microorganisms grow in the headspace. Modified atmosphere packaging (MAP) replaces the air inside a sealed tray with a controlled gas mixture, extending shelf life by days or weeks without relying on preservatives. Getting it right depends on the tray, the film, the seal and the gas working together.

How MAP Works

A tray is filled, flushed with a gas mix and heat-sealed with lidding film in one step. The atmosphere inside then changes slowly as the product respires or absorbs gas, and as gases permeate through the pack. The barrier of the pack decides how long the target mixture lasts. A pack that lets oxygen in too quickly defeats the purpose.

Common Gas Mixes

Product	Typical gases	Role of each gas
Red meat	High oxygen plus carbon dioxide	Oxygen keeps the bright red colour; CO₂ slows bacteria
Poultry	Carbon dioxide plus nitrogen	CO₂ inhibits spoilage bacteria; N₂ fills headspace so the pack does not collapse
Fish	Higher CO₂, low or no oxygen	Controls bacteria; oxygen avoided to limit oxidation
Ready meals, pasta	Nitrogen plus CO₂	Limits oxidation and mould growth
Fresh-cut produce	Reduced oxygen with controlled CO₂, often with micro-perforation	Balances respiration with gas exchange

Exact mixes and ratios depend on the product, microbiology and country rules. They should be set with the food technologist or packer, not by the packaging supplier alone.

Barrier: The Number That Matters

Barrier is measured as oxygen transmission rate (OTR), in cc of oxygen per square metre per day, and water vapour transmission rate (WVTR). Lower OTR means better barrier. A rough guide, with typical values varying by thickness and test conditions:

Standard APET or PP tray without barrier: relatively high OTR; fine for short-life chilled food and fruit that needs to breathe.
Barrier tray with EVOH layer: an ethylene vinyl alcohol layer sandwiched inside the tray wall cuts OTR dramatically. This is the standard for fresh meat, fish and cheese MAP.
PA/PE or PET/PE with barrier layers for lidding film: film also needs low OTR, and often anti-fog treatment. The weakest of tray and film sets the pack's barrier.

EVOH is sensitive to moisture, so it is buried between layers of PP, PET or PE. For that reason barrier trays are laminated or co-extruded, not mono-layer, which affects both cost and recyclability. See PET vs PP vs rPET for base-material trade-offs.

Choosing the Tray

Base polymer. APET for clear fresh display, PP for heat resilience and microwave, CPET for dual-ovenable ready meals. See CPET vs PP.
Barrier layer. Specify EVOH or other barrier by target OTR, not just by name.
Rigidity and flange. Flat, wide flanges seal better. Check flange flatness on arrival.
Absorbent pad. Meat and poultry trays often include an absorbent pad for exudate. See the meat tray buying guide.
Anti-fog and clarity. For consumer display, anti-fog on the film is critical.

Choosing the Lidding Film

Match the film sealing layer to the tray (for example PE-based seal layer for PE-compatible tray surfaces).
Choose peelable or weld seal depending on whether the consumer must open it by hand. Closure options are covered in the leak-proof packaging guide.
Specify OTR and WVTR at the actual storage temperature and humidity, since both rise as temperature rises.
Confirm printing and overprint varnish compatibility with the sealing machine.

Seal Integrity Is Everything

A tiny leak lets the gas out and air in, so shelf life collapses. Key controls:

Clean flange with no product contamination at the seal.
Correct seal temperature, pressure and dwell time for the film and tray pair.
Residual oxygen checked with a gas analyser at the start and during runs.
Leak testing by water immersion or a pressure test on samples from each run.

Shelf-Life Trials

Do not trust a brochure number. Run a trial with the real product, tray, film, gas mix and storage temperature. Measure microbiology, colour, odour and pack integrity at intervals until the product fails, then set the shelf life with a safety margin. Cold-chain breaks shorten life dramatically, so include a temperature-abuse test if the supply chain is uncertain. For quality checks on received packaging, see the AQL inspection guide.

Compliance and Documentation

The tray, film, adhesive and ink all need food-contact compliance for the intended food type, and multilayer barrier structures should be assessed as a whole. Request declarations of compliance and migration test results, and see the FDA and EU guides. Our factory operates under ISO 9001:2015 and BRCGS Packaging, and SGS reports can be provided for finished trays.

Specification Checklist

Product, fill weight and target shelf life at stated temperature.
Tray size, depth, base polymer and target OTR.
Lidding film structure, OTR, anti-fog and seal type.
Gas mix and sealing machine model.
Compliance documents needed for the destination market.

Send the checklist to our team and we will recommend barrier trays and matching films, with samples to run your shelf-life trial.

Buyer FAQ

What is modified atmosphere packaging?

A method that replaces the air in a sealed pack with a controlled gas mixture, typically oxygen, carbon dioxide and nitrogen in various ratios, to slow spoilage and extend shelf life.

Why do MAP trays need an EVOH layer?

EVOH is a high-barrier polymer that sharply reduces oxygen entering the pack, so the gas mixture lasts for the full shelf life. It is placed inside the tray wall because it is sensitive to moisture.

Can I use a normal PET or PP tray for MAP?

For short shelf lives, sometimes. For meat, fish and other products that need a long shelf life, a barrier tray and a high-barrier lidding film are normally required.

What gas is used for fresh meat?

Red meat often uses a high-oxygen mix with carbon dioxide to keep colour and slow bacteria, while poultry and fish usually use carbon dioxide with nitrogen. Mixes should be set by your food technologist.

How do I confirm my MAP shelf life?

Run a real trial with the exact product, tray, film, gas mix and storage temperature, monitoring microbiology, colour, odour and pack integrity until failure, then apply a safety margin.