Evaporation Residue Testing of Packaging Materials: Standards, Methods, and Regulatory Compliance

Evaporation residue testing is a fundamental safety assessment for food packaging materials, quantifying the total amount of non-volatile substances that migrate from packaging into food simulants under controlled conditions. This gravimetric test is mandated by major regulatory frameworks worldwide, including the Chinese national food safety standards (GB 4806 series), the U.S. FDA regulations (21 CFR), and the EU plastics regulation, making it essential for manufacturers, converters, and importers seeking market access. This article provides a comprehensive technical overview of evaporation residue testing, covering applicable sample types, testing items, methodologies, and frequently asked questions.

Technical Overview

Evaporation residue (also referred to as total migrate quantity or overall migration in modern regulatory terminology) measures the total mass of non-volatile substances released from a packaging material into a food simulant under specified time and temperature conditions. The test liquid obtained after the migration exposure is evaporated to dryness, and the remaining residue is dried to constant mass and weighed using a precision analytical balance. The result reflects the combined migration of all extractable, non-volatile components, including residual monomers, oligomers, plasticizers, antioxidants, slip agents, processing aids, and degradation products.

Excessive evaporation residue indicates that a packaging material releases an unacceptably high quantity of substances into food, which can affect food quality, alter taste and odor, and pose potential health risks to consumers. For this reason, virtually every regulatory regime governing food contact materials establishes quantitative limits for this parameter. In China, the current method standard is GB 31604.8-2016 (determination of total migration quantity), supported by the general migration testing rules in GB 31604.1 and GB 5009.156, while product limits are defined in the GB 4806 series. These superseded the legacy methods such as GB/T 5009.60-2003, although the underlying gravimetric principle remains unchanged. In the European Union, the equivalent parameter is overall migration under Regulation (EU) No 10/2011, tested according to the EN 1186 series of standards. In the United States, the FDA addresses the same concern through total extractives limits specified in the individual resin and application clauses of 21 CFR 174-179.

As a gravimetric, non-selective screening test, evaporation residue serves as a first-line indicator of material safety. Elevated results typically trigger further targeted analysis of specific migrants using chromatographic techniques.

Testing Samples

Evaporation residue testing applies to a broad spectrum of packaging and food contact materials. Samples are typically submitted as finished articles, representative sheeting, or production samples, and testing is performed on the food-contact side whenever the article geometry permits.

Plastic Films, Sheets, and Laminates

Flexible packaging materials such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA), polystyrene (PS), and multilayer laminates for pouches, wraps, and bags are among the most frequently tested categories. Film and sheet samples are well suited to the cell method or pouch method, which expose only the functional food-contact surface to the simulant.

Rigid Plastic Containers and Articles

Bottles, jars, cups, trays, tubs, closures, cutlery, straws, and other molded articles are tested using the filling method, in which the simulant is filled into the container to a level representing the actual food contact condition. This approach realistically reproduces the intended surface-area-to-volume relationship.

Paper and Paperboard

Paper-based packaging such as cartons, cups, boxes, and wrapping paper, including coated and treated grades, is evaluated for total migration into aqueous, acidic, alcoholic, and fatty food simulants in accordance with the applicable product standard in the GB 4806 series for paper and board.

Rubber and Elastomeric Articles

Seals, gaskets, nipples, tubing, and other rubber components used in packaging, dispensing systems, and food processing equipment are tested for evaporation residue given the comparatively high extractable content of elastomeric formulations and their curing systems.

Coatings, Can Linings, and Composite Materials

Epoxy-phenolic and other protective coatings on metal cans, coated films, and metallized laminates are assessed to verify that coating formulation and curing conditions do not produce excessive non-volatile migrants into canned or retorted foods.

Biodegradable and Specialty Materials

Polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), starch blends, and other emerging materials require careful residue evaluation because degradation by-products and additives may migrate more readily than in conventional polyolefins, particularly at elevated use temperatures.

Testing Items

The core testing items for evaporation residue assessment are differentiated by food simulant and by exposure condition, reflecting the full range of intended food-contact applications:

• Evaporation residue in water (aqueous foods with pH above 5, such as beverages, soups, and drinking water)
• Evaporation residue in 4% acetic acid (acidic foods with pH below 5, such as vinegar, juice, and fermented products)
• Evaporation residue in ethanol-based simulants, typically 10%, 20%, 50%, or 95% ethanol depending on the alcoholic and lipid character of the intended food
• Evaporation residue in n-hexane, n-heptane, or isooctane (fatty and oily foods under accelerated conditions)
• Overall migration into olive oil or substitute solvents for fatty food contact under EU protocols
• Condition-specific testing at elevated temperatures, including hot-fill (e.g., 70°C), boiling water (100°C), and retort or sterilization conditions (e.g., 121°C) exposure scenarios
• Migration testing with chemical alternative solvents using time-temperature compensation factors in place of vegetable oil
• Full compliance verification combining evaporation residue with specific migration, heavy metals, and sensory testing as required by the applicable product standard

Testing Methods

Food Simulant Selection

The choice of simulant is dictated by the intended food type as classified in the migration testing general rules. Aqueous foods are represented by water or dilute ethanol, acidic foods by 4% acetic acid, alcoholic foods by aqueous ethanol at the appropriate concentration, and fatty foods by n-hexane, isooctane, or vegetable oil. Test conditions (temperature and duration) are selected to reproduce or accelerate the most severe foreseeable use, for example 40°C for 24 hours for long-term ambient storage, 70°C to 100°C for hot filling and pasteurization, and 121°C for 30 minutes or longer for retort applications.

Exposure Techniques

Four principal exposure configurations are recognized in the method standards:

• Total immersion method: the cut specimen is fully immersed in simulant at a standardized surface-area-to-volume ratio; suitable for materials, irregular articles, and comparative screening
• Cell method: the simulant is confined against one defined surface of a flat specimen using a test cell; appropriate when the reverse side is a non-contact surface such as an outer printing layer
• Pouch method: the film is heat-sealed into a pouch that is filled with simulant; representative of actual flexible packaging geometry
• Filling method: the simulant is filled directly into the finished container or article under its intended fill condition

Evaporation, Drying, and Gravimetric Determination

Following the exposure period, a measured aliquot of the migration test liquid is transferred into a pre-conditioned evaporating dish (glass or porcelain) that has been dried to constant mass. The simulant is evaporated gently, typically on a controlled water bath and inside a fume hood for flammable solvents such as hexane, heptane, isooctane, and ethanol. The dry residue is then heated in a drying oven at 100°C to 105°C for approximately two hours, cooled to ambient temperature in a desiccator, and weighed on an analytical balance with 0.1 mg readability. The drying, cooling, and weighing cycle is repeated until consecutive masses differ by no more than the constant-mass criterion specified in the method. A reagent blank is prepared and processed identically using the same volume of pristine simulant, and the blank value is subtracted from the sample result to correct for simulant impurities and environmental contributions.

Calculation and Expression of Results

The corrected residue mass is expressed in units appropriate to the applicable regulatory framework, most commonly milligrams per liter of simulant (mg/L), milligrams per square decimeter of contact surface (mg/dm²), or milligrams per kilogram of food (mg/kg), with conversions based on the standardized contact area-to-volume ratio used during exposure. Parallel determinations are performed, and the arithmetic mean is reported together with the test conditions. Under the GB 4806 product standards, typical acceptance criteria for plastics, paper, coatings, and rubber are 10 mg/dm², with a limit of 60 mg/kg applied to small or large containers and to articles intended for infant food contact, consistent with the overall migration limit structure used in the EU under Regulation (EU) No 10/2011. FDA-regulated articles are evaluated against the total extractives limits stated in the relevant 21 CFR clause, commonly expressed per unit area of contact surface.

Applicable Standards and Regulatory References

• GB 31604.8-2016: National food safety standard for the determination of total migration quantity of food contact materials and articles
• GB 31604.1 and GB 5009.156: General rules for migration testing, covering simulant selection, test conditions, and area-to-volume conventions
• GB 4806 series: Product standards for plastics (GB 4806.7), paper and board (GB 4806.8), coatings (GB 4806.10), rubber (GB 4806.11), and other material categories, which define the applicable limits
• EN 1186 series: European standard methods for overall migration into food simulants by immersion, cell, pouch, and filling techniques
• Regulation (EU) No 10/2011: EU plastics regulation establishing the overall migration limit and test condition conventions
• 21 CFR 174-179: FDA food contact substance regulations specifying extraction conditions and total extractives limits by condition of use
• Japanese Food Sanitation Act specifications for utensils, containers, and packaging, which define evaporation residue limits for each polymer category

Applications

Evaporation residue testing supports a wide range of commercial and regulatory objectives across the packaging supply chain:

• Regulatory compliance demonstration for food contact materials placed on the Chinese market under the GB 4806 national food safety standards
• Export certification support for packaging destined for the EU, the United States, Japan, and other jurisdictions, with test plans tailored to the destination framework
• Raw material qualification and incoming inspection by packaging converters, ensuring that resins, films, adhesives, and coatings meet internal and customer specifications before production
• New product development and formulation comparison, where residue data help optimize additive loading, curing parameters, and laminate structures
• Validation of high-temperature applications, including retort pouches, hot-fill bottles, microwave packaging, and ovenable trays
• Verification of biodegradable and recycled-content materials, where processing history and degradation can increase extractable content
• Support for compliance declarations, positive-list conformity files, and submissions to accredited third-party laboratories for independent verification
• Investigation of customer complaints related to off-odor, taste transfer, or visible contamination traceable to packaging constituents

FAQ

What is the difference between evaporation residue and overall migration?

The two terms describe the same physical measurement: the total non-volatile mass transferred from the material into a food simulant. Evaporation residue is the traditional terminology retained in Chinese and Japanese regulations, while overall migration is the term used in the EU framework. The result is obtained identically by gravimetric determination after solvent evaporation.

Why are multiple simulants used instead of real food?

Real foods are heterogeneous and cannot be evaporated cleanly to a dry residue. Food simulants are simple, well-characterized liquids with documented extraction behavior that represent broad food categories, enabling reproducible, comparable, and analytically practical measurements across laboratories.

How are test conditions such as temperature and time selected?

Conditions are selected according to the worst foreseeable use of the packaging, following the convention tables in the applicable general rules standard. For example, a retort pouch intended for 121°C sterilization is tested at 121°C for the corresponding duration, while a pouch for ambient storage may be tested at 40°C for 24 hours.

What sample quantity is required for testing?

Testing typically requires finished articles or sheet material sufficient to provide the standardized contact area for each simulant and condition combination, generally on the order of several square decimeters per test plus retention samples. Exact requirements depend on the article geometry and the number of simulants and conditions in the test plan.

What does an out-of-specification result mean and how is it addressed?

A failing result indicates that the material releases more total non-volatile matter than the applicable limit permits. Follow-up actions include confirming the result with a retest, reviewing formulation and processing (additive levels, residual monomer, curing or annealing conditions), and, where required, conducting specific migration analysis to identify the dominant contributors and demonstrate conformity through corrective reformulation.

How long does evaporation residue testing take?

The exposure phase ranges from 30 minutes for high-temperature accelerated conditions to 10 days for long-term storage simulation, followed by evaporation, drying, and weighing cycles over one to two additional days. Complete multi-simulant, multi-condition test packages are therefore commonly completed within two to four weeks, including reporting.