Determination of Evaporation Residue in Plastic Containers: Standards, Methods, and Compliance Testi

Evaporation residue testing measures the total mass of non-volatile substances that migrate from plastic food-contact containers into food simulants under controlled time and temperature conditions, making it one of the most critical safety indicators in food packaging compliance. This article explains the regulatory requirements under GB 4806.7-2016, GB 31604.8-2021, EU Regulation (EU) No 10/2011, and FDA 21 CFR, along with applicable sample types, testing items, laboratory procedures, calculation methods, and frequently asked questions.

Technical Overview

Evaporation residue refers to the total mass of non-volatile substances that transfer from a plastic container into a food simulant under specified time and temperature conditions, expressed in mg/L (per volume of simulant) or mg/dm² (per contact area). The residue typically comprises a complex mixture of residual monomers, oligomers, plasticizers, antioxidants, slip agents, lubricants, colorant carriers, and processing aids that are not chemically bound to the polymer matrix.

Rather than identifying each individual substance, evaporation residue testing functions as a holistic screening parameter: an elevated result signals excessive overall transfer of low-molecular-weight extractables into food, which may affect food safety, flavor, and odor quality. In China, the permissible level is regulated under GB 4806.7-2016 (National Food Safety Standard for Food Contact Plastic Materials and Articles), with the measurement procedure specified in GB 31604.8-2021 and migration pretreatment rules in GB 5009.156-2016.

Internationally, the equivalent concepts are the overall migration limit (OML) under EU Regulation (EU) No 10/2011 and the EN 1186 series of methods, and the total extractives test under FDA 21 CFR 175.300 and 21 CFR 176.170. Accredited third-party laboratories routinely perform evaporation residue determination for market access in China, the European Union, the United States, and other jurisdictions.

Testing Samples

Polyolefin Containers (PE and PP)

Blow-molded and injection-molded containers made of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), including beverage bottles, condiment bottles, yogurt cups, storage boxes, and microwave-safe food containers. These materials frequently contain antioxidants and slip agents that contribute to extractable residue.

Polyethylene Terephthalate (PET) Containers

Beverage bottles, edible oil bottles, sauce jars, and thermoformed trays. Testing focuses on oligomer release and residues of catalysts, stabilizers, and acetaldehyde-related extractables.

Polystyrene and ABS Containers

Cold-drink cups, food service trays, and disposable tableware made of general-purpose or high-impact polystyrene (GPPS, HIPS) and acrylonitrile butadiene styrene (ABS), where residual styrene monomer and oligomers are of primary concern.

Polyvinyl Chloride (PVC) Containers

Bottles and films for edible oils and acidic foods. PVC formulations may contain plasticizers and thermal stabilizers with significant migration potential, making residue control essential.

Polycarbonate and Engineering Polymer Containers

Water dispenser bottles, baby bottles, and heat-resistant tableware made of polycarbonate (PC), Tritan copolyesters, and polyamide, evaluated for bisphenol-related and oligomeric extractables in addition to total residue.

Biodegradable and Multilayer Composite Containers

Containers based on polylactic acid (PLA), PBAT, or starch blends, as well as multilayer laminated cups, pouches, and bowls containing adhesive and barrier layers, all of which introduce additional migratable components that must be assessed.

Testing Items

Evaporation residue is determined separately for each food simulant selected according to the intended food type and use condition of the container. Typical test items include:

• Evaporation residue in water (simulant for neutral aqueous foods)
• Evaporation residue in 4% acetic acid or 3% acetic acid (acidic foods)
• Evaporation residue in 10%, 20%, 50%, 65%, or 95% aqueous ethanol (alcoholic and lipophilic foods)
• Evaporation residue in isooctane or n-heptane (fatty food simulants or substitute simulants)
• Overall migration into vegetable oil or approved oil substitutes for EU compliance
• Total extractives in water, aqueous ethanol, and n-heptane for FDA compliance

Common exposure conditions selected per GB 5009.156-2016 or EN 1186 include 60 °C for 30 minutes for general-purpose containers, 95 °C for 30 minutes or 100 °C for 1 hour for hot-fill and pasteurized products, and 40 °C for 24 hours for long-term ambient storage. Under GB 4806.7-2016, the evaporation residue limit is 30 mg/L for the specified simulants; the EU overall migration limit is 10 mg/dm² of food-contact surface (or 60 mg/kg for small containers); FDA total extractives limits typically range up to 0.5 mg/in² depending on the condition of use.

Testing Methods

Principle

The container or material specimen is exposed to a food simulant under controlled time and temperature conditions. A measured aliquot of the migration solution is then evaporated to dryness in a preconditioned glass dish, and the non-volatile residue is dried to constant mass at 105 °C and weighed on an analytical balance. After blank correction, the residue mass is calculated per unit volume of simulant (mg/L) or per unit contact area (mg/dm²).

Sample Preparation

Representative containers are selected from production lots, rinsed with water, and air-dried without solvent wiping. Fillable containers are filled with simulant to within approximately 0.5 to 1 cm of the brim; flat or cut materials are fully immersed at a surface-area-to-volume ratio of approximately 2 mL/cm². The contact area or fill volume is recorded for result calculation. Sealed vessels or migration cells are used for volatile simulants such as 95% ethanol and isooctane to prevent loss during exposure.

Migration Exposure

Specimens are held in thermostatically controlled incubators or water baths at the selected condition, for example 60 °C for 30 minutes, 95 °C for 30 minutes, or 40 °C for 24 hours, with temperature maintained within ±1 °C of the set point. The most severe foreseeable use condition is chosen to reflect worst-case migration behavior.

Evaporation, Drying, and Weighing

A measured aliquot of the migration solution (commonly 200 mL) is transferred into a glass evaporating dish previously conditioned to constant weight. The solution is evaporated to near dryness on a water bath, with dish walls rinsed down using small portions of the same simulant to consolidate the residue. The dish is then dried at 105 °C ± 2 °C for about 2 hours, cooled in a desiccator for 30 minutes, and weighed. Drying, cooling, and weighing cycles are repeated until the mass difference between consecutive weighings is within the constant-weight criterion (typically 0.5 mg or less). A reagent blank using the same simulant without any specimen is processed in parallel for correction.

Calculation

The evaporation residue is calculated as: X (mg/L) = (m1 − m2) × 1000 / V, where m1 is the residue mass from the sample migration solution (mg), m2 is the residue mass of the reagent blank (mg), and V is the volume of the aliquot (mL). For area-based reporting, the result is converted using the measured contact area or the conventional ratio of 6 dm² per kilogram of food applied in EU overall migration assessment.

Quality Control

• Use analytical balances with 0.1 mg readability and calibrated glassware for all volumetric transfers.
• Precondition all dishes to constant weight before use and handle them with tongs or gloves to prevent contamination.
• Perform determinations in duplicate or triplicate and evaluate reproducibility against the acceptance criteria of the applied method.
• Apply mandatory blank correction and verify simulant identity, concentration, and expiry before each test series.
• Document exposure time, temperature, contact area, and fill volume to ensure traceable and defensible reporting.

Applications

Evaporation residue determination is a core requirement across the lifecycle of plastic food-contact containers:

• Regulatory compliance and market access: demonstrating conformity with GB 4806.7-2016 for the Chinese market, EU Regulation (EU) No 10/2011 for Europe, and FDA 21 CFR 175.300 and 176.170 for the United States.
• Product development: screening polymer formulations, additive packages, and processing aids during design and before mass production.
• Manufacturing quality control: verifying lot-to-lot consistency of incoming resins and finished containers, and investigating deviations related to mold release agents or overheating.
• Export and customs clearance: providing test reports accepted by importers and supervisory authorities in destination markets.
• Regulatory supervision: supporting national food-safety monitoring programs and risk assessment of food-contact materials.
• Special-use qualification: validating containers intended for hot filling, microwave heating, sterilization, or long-term storage at elevated temperatures.

FAQ

What is evaporation residue and why is it important?

Evaporation residue is the total mass of non-volatile substances that migrate from a plastic container into a food simulant. It is important because it provides an aggregate measure of extractable content, indicating whether excessive amounts of additives, oligomers, or unreacted components could transfer into food during real-world use.

What is the regulatory limit for evaporation residue?

Under GB 4806.7-2016, the limit for plastic materials and articles is 30 mg/L for the specified food simulants and conditions. The EU overall migration limit under Regulation (EU) No 10/2011 is 10 mg/dm², while FDA total extractives limits under 21 CFR 175.300 and 176.170 vary by condition of use and simulant.

How does evaporation residue differ from overall migration and total extractives?

The three concepts are technically analogous but arise from different regulatory frameworks. Evaporation residue is the Chinese GB parameter, overall migration is the EU measure expressed per contact area, and total extractives is the FDA measure expressed per surface area of the finished article. All rely on simulant extraction followed by gravimetric quantification of non-volatile residue.

Which simulants and test conditions apply to my container?

Simulant selection follows the intended food type: water or 10% ethanol for neutral aqueous foods, acetic acid solutions for acidic foods, aqueous ethanol for alcoholic foods, and isooctane, n-heptane, or vegetable oil for fatty foods. Test conditions mirror the worst foreseeable use, such as 60 °C for 30 minutes for room-temperature service or 95 °C for 30 minutes for hot-fill applications, as defined in GB 5009.156-2016 and the EN 1186 series.

How much sample is required and how long does testing take?

Most methods require a minimum of several complete containers or a sufficient sheet area to provide the required simulant volume in duplicate, typically equivalent to 400 mL or more per simulant per condition. Standard turnaround at accredited third-party laboratories is generally 7 to 10 working days, depending on the number of simulants and exposure conditions selected.

What causes high evaporation residue and how can it be reduced?

Common causes include excessive antioxidant or lubricant loading, incompletely cured or devolatilized polymer, high levels of oligomers, contaminated masterbatch, or overly severe process temperatures. Reduction strategies include optimizing additive formulations, increasing devolatilization, adjusting molding conditions, and switching to higher-purity resins or food-grade grades compliant with GB 4806.6.

Are biodegradable containers such as PLA also tested?

Yes. Biodegradable polymer containers are subject to the same evaporation residue requirements under GB 4806.7-2016 when used for food contact, and their oligomer-rich compositions make residue testing particularly important during formulation development and certification.