Overall migration testing measures the total quantity of non-volatile substances that transfer from food contact packaging materials into food simulants under controlled time and temperature conditions. As a core compliance requirement under regulations such as EU Regulation (EU) No 10/2011, EN 1186, and GB 4806 series standards, this gravimetric determination is essential for manufacturers, suppliers, and accredited third-party laboratories verifying the safety of packaging intended for food contact. This article explains the technical principles, sample types, testing items, methodology, and practical applications of overall migration determination.
Technical Overview
Overall migration (OM), also referred to as total migration, quantifies the cumulative mass of all non-volatile substances released from a food contact material into a food simulant under standardized test conditions. Unlike specific migration, which targets individual compounds such as bisphenol A or phthalates, overall migration provides a global indicator of material inertness. The determination is performed gravimetrically: the food simulant that has been in contact with the test specimen is evaporated to dryness, and the dry residue is weighed to constant mass. The result is expressed in milligrams per square decimeter of contact surface (mg/dm²) or, for containers intended to hold a known volume of food, in milligrams per kilogram of food (mg/kg).
Regulatory frameworks worldwide have established migration limits based on this measurement. In the European Union, Regulation (EU) No 10/2011 sets a default overall migration limit (OML) of 10 mg/dm² of food contact surface, or 60 mg/kg when the container holds more than 500 mL or less than 500 mL with an undefined surface area. In China, GB 4806.1 and the method standard GB 31604.8 specify a comparable limit of 10 mg/dm² for food contact materials. The harmonized European method standards are found in the EN 1186 series for plastics, while paper, board, rubber, coatings, and other substrate categories are covered by their respective EN and GB method standards.
Testing Samples
Plastic Materials and Articles
Films, sheets, rigid containers, closures, laminates, and multilayer structures made from polyolefins, PET, PVC, PS, PLA, and other polymers represent the largest category of samples. Both monolayer and multilayer laminates are tested, with the food contact layer oriented toward the simulant during exposure.
Coatings and Coated Substrates
Can coatings, varnishes, lacquers on metal substrates, silicone-coated papers, and polymer-coated films are tested to evaluate the migration contribution of the coating system together with the underlying substrate.
Rubber and Elastomeric Articles
Seals, gaskets, O-rings, nipples, and flexible tubing used in food processing equipment and packaging closures are evaluated because elastomers typically contain higher levels of additives and plasticizers.
Paper and Paperboard
Direct food contact papers, paperboard cartons, molded pulp trays, and paper-based baking materials are tested, often in combination with barrier coating assessments.
Metal Packaging and Metallized Films
Aluminum foils, steel cans, metallized polymer films, and other metallic articles are tested to verify the integrity and inertness of protective coatings and surface treatments.
Glass, Ceramics, and Biobased Materials
Although inert glass and ceramics are more commonly assessed for heavy metal release, surface-treated glass and emerging biobased or biodegradable polymer packaging are increasingly subject to overall migration evaluation.
Testing Items
The overall migration determination encompasses several distinct test parameters that must be defined before testing begins:
- Overall migration limit (OML) verification against 10 mg/dm² or 60 mg/kg regulatory thresholds
- Overall migration into aqueous food simulants (10% ethanol, 3% acetic acid)
- Overall migration into alcoholic simulants (20% and 50% ethanol)
- Overall migration into fatty food simulants (vegetable oil, e.g., refined olive oil)
- Overall migration using substitute simulants (isooctane, 95% ethanol, 50% ethanol) for materials incompatible with oil
- Migration at accelerated or long-term storage conditions, covering refrigerated, room temperature, hot fill, and sterilization scenarios
Testing Methods
Selection of Food Simulants
Food simulants are standardized media chosen to represent the chemical behavior of real foods. Under EU Regulation (EU) No 10/2011: simulant A (10% ethanol) represents aqueous non-acidic foods, simulant B (3% acetic acid) represents acidic aqueous foods, simulants C (20% ethanol) and D1 (50% ethanol) represent alcoholic and dairy-type foods, and simulant D2 (vegetable oil) represents fatty foods. When vegetable oil cannot be applied analytically, for example with materials that absorb oil excessively, substitute simulants such as isooctane and 95% ethanol are used with reduced contact times calculated through equivalence factors.
Selection of Test Conditions
Test time and temperature must realistically simulate worst foreseeable use. Typical condition sets include 10 days at 20°C or 40°C for long-term room temperature storage, 2 hours at 70°C or higher for hot fill applications, and conditions reaching 121°C or above for retort sterilization. The chosen condition must correspond to the maximum shelf life and thermal history declared for the packaged food.
Exposure Techniques
Four principal exposure configurations are defined in EN 1186 and GB 31604.8:
Total immersion method: the specimen is fully immersed in simulant, suitable for films, sheets, and cut pieces where total surface area is known
Pouch method: the specimen is sealed into a pouch that is filled with simulant, appropriate for flexible films evaluated on the food contact side only
Cell method: simulant is held in a test cell against one defined surface of the specimen, used for rigid sheets and asymmetric laminates
Filling method (article filling): the finished container is filled with simulant to a defined headspace, reflecting actual use for bottles, cups, trays, and cans
Gravimetric Determination Procedure
After the exposure period, the simulant is transferred quantitatively to a preconditioned evaporation dish and evaporated to near dryness on a water bath or hot plate, then dried in a desiccator and oven to constant mass. The residue mass is corrected using blanks prepared from unexposed simulant and, where required, extraction and back-extraction procedures are applied for oily simulants. The overall migration value is calculated by dividing the corrected residue mass by the exposed surface area, with results compared against the applicable OML.
Quality Control and Reporting
Method blanks, duplicate determinations, and controlled ambient conditions (typically 20°C ± 2°C laboratory temperature, humidity control for hygroscopic residues) are required. Test reports must state the simulant, exposure configuration, time and temperature condition, surface-to-volume ratio, correction factors applied, and the final migration value with its measurement uncertainty.
Applications
Overall migration testing serves multiple commercial and regulatory purposes across the packaging supply chain:
- Regulatory compliance demonstration for food contact materials entering the EU market under Regulation (EU) No 10/2011 and framework Regulation (EC) No 1935/2004
- Compliance with Chinese national standards GB 4806.1, GB 4806.7 (plastics), and GB 9685 for additives, verified through GB 31604.8 method procedures
- Support for Declarations of Compliance (DoC) issued by material manufacturers to converters and food packers
- Incoming quality control and supplier verification for brand owners and food producers
- Product development screening of new resin formulations, coatings, adhesives, and biobased materials prior to market launch
- Export certification packages prepared with accredited third-party laboratories for multi-market access, including references to FDA 21 CFR approaches for the United States
- Migration behavior studies supporting shelf life validation and high-temperature application qualification
FAQ
What is the difference between overall migration and specific migration? Overall migration measures the collective mass of all substances transferring into the simulant, reported as a single gravimetric value, while specific migration quantifies individually named substances using instrumental techniques such as HPLC, GC-MS, or ICP-MS against substance-specific limits.
What happens if a sample fails the 10 mg/dm² limit? A confirmed exceedance means the material cannot be declared compliant for the tested food type and use condition. Corrective actions include reformulation, adding or improving barrier layers, restricting intended use conditions, or re-testing with a more representative simulant under a justified condition.
Why are substitute simulants sometimes used instead of vegetable oil? Some materials absorb oil or physically interact with it in ways that make gravimetric determination unreliable, so isooctane or 95% ethanol is used with shortened exposure times derived from documented correlation factors to maintain test validity.
How is the surface area determined for finished containers? For the filling method, the entire inner surface in contact with the simulant is measured geometrically, or alternatively the result is expressed as mg/kg based on the declared filling volume and food mass, which is permitted for containers with a conventional capacity between 500 mL and 10 L under EU rules.
How long does overall migration testing take? Standard 10-day immersion tests typically require two to three weeks including conditioning, exposure, evaporation, and constant-weight verification. High-temperature sterilization conditions compress the exposure period but extend preparation and equilibration steps.
Can overall migration results alone demonstrate full compliance? No. Overall migration is a foundational screening parameter that must be combined with specific migration testing for listed restricted substances, residual quantity checks, and appropriate declarations to establish complete regulatory conformity for food contact materials.