🍎 Overall migration from plastics into aqueous food simulants — total immersion, the gravimetric method

Food chemistry PN-EN 1186-3

Overview

The standard of the EN 1186 series specifies methods of testing the overall migration from plastics intended for contact with food. The edition EN 1186-3:2002, on which the description is based, concerned migration into aqueous food simulants by the total immersion of the test specimens in the simulant at temperatures up to boiling under reflux (method A — in a drying oven, an incubator or a refrigerator; method B — under reflux); it is the most suitable for films and sheets, but it may be applied to a wide range of articles and containers from which specimens can be cut. The current edition PN-EN 1186-3:2023-01 (EN 1186-3:2022) bears the title "Metody badań ogólnej migracji w wyparowujących płynach modelowych" [Test methods for overall migration in evaporable simulants] — its full text was not available to us and before implementation the changes of the scope have to be checked. The standard is used together with EN 1186-1 (the choice of the conditions and the methods of testing).

The overall migration is the sum of the non-volatile low-molecular constituents of the packaging released into the food or into the simulant imitating the action of a given kind of food; the permissible limit is 10 mg/dm² of the surface of the article or 60 mg/kg of the foodstuff. The simulants: A — distilled water (hydrated food of pH > 4.5), B — 3 % acetic acid (acid food, pH ≤ 4.5), C — 10 % ethanol (food with alcohol; for drinks of a strength above 10 % — ethanol of a similar strength); the dry residue of the simulant itself after evaporation and drying at 105–110 °C should not exceed 5 mg/l. The conditions of the test are chosen for the most severe conditions of contact foreseen; the standard conditions of 10 days at 40 °C and the alternative ones of 2 days at 70 °C gave in the studies of the National Institute of Public Health equivalent results for polyamide casings and polystyrene cups (0.1–2.9 mg/dm²), whereas a multilayer film released into 3 % acetic acid 238.4–262.2 mg/dm², exceeding the limit many times over.

Besides immersion, the series of the standard provides for the cell method (part 5), the pouch method (part 7) and the filling method (part 9) — the choice depends on which surface of the article is in contact with the food; articles for repeated use are tested three times with the same specimen with a fresh portion of simulant, and compliance is assessed after the third test.

Method principle

The overall migration of non-volatile substances is determined as the mass of the non-volatile residue after the evaporation of the simulant in which the test specimens were immersed. Specimens of an area of about 1 dm² (films: a square of 100 × 100 mm from a template, cut into four strips of 25 × 100 mm placed on a holder of stainless steel X4 CrNi 18 10 or of glass; the walls of containers — cut-outs of a measured area to 0.01 dm²) are immersed in the simulant in glass tubes with a ground joint (diameter about 35 mm, length 100–200 mm) for the time of exposure at temperatures up to and including boiling; between thin films a stainless steel mesh (1 mm aperture) or glass rods are inserted (with acetic acid — glass, because the acid corrodes steel). After the exposure the simulant from each specimen is evaporated to dryness (a steam bath, a hotplate, a rotary evaporator) in an evaporating dish of stainless steel, nickel, platinum or gold (50–90 mm, up to 100 g; glass or ceramic, if the mass after drying is constant within ±0.5 mg), dried in a drying oven to constant mass and weighed to the nearest 0.1 mg; in parallel the simulant itself is evaporated (a reagent blank). The migration M = (ma − mb)·1000/S [mg/dm²], where ma is the mass of the residue of the specimen (g), mb the mass of the residue of the reagent blank (g), S the area of the specimen in contact with the simulant (dm²). The result is given as the mean of three determinations on separate specimens.

Applications

• Assessment of the conformity of packaging, films and containers of plastics with the overall migration limit of 10 mg/dm² (60 mg/kg)
• Testing of casings for cured meats, cups for dairy products, pouches and multilayer films under the conditions of real use (also after the heat treatment of the product in the packaging)
• Documentation of the declaration of compliance of a producer of materials for contact with food
• Official control of materials and articles for contact with food (the State Sanitary Inspection)
• Qualification of the simulant and of the conditions of testing for hydrated, acid and alcoholic food

Key parameters

Standard

Standard number

PN-EN 1186-3:2023-01

Title (PL)

Materiały i wyroby przeznaczone do kontaktu z produktami spożywczymi — Tworzywa sztuczne — Część 3: Metody badań ogólnej migracji w wyparowujących płynach modelowych

Title (EN)

Materials and articles in contact with foodstuffs — Plastics — Part 3: Test methods for overall migration in evaporable simulants

Step-by-step procedure

1. Choice of the conditions

   In accordance with EN 1186-1 choose the simulant according to the kind of food (A, B, C) and the time and the temperature corresponding to the most severe conditions of use foreseen (for example 1 h at 80 °C + 10 days at 40 °C for casings subjected to heat treatment; as standard 10 days at 40 °C or 2 days at 70 °C).

2. Preparation of the specimens

   Remove the contamination of the surface with a dry lint-free cloth or a soft brush (do not wash with water or a solvent, unless the instructions for the use of the article provide for washing); work in cotton gloves. Films: cut from the template three specimens of 100 × 100 mm (±1 mm), cut each into four strips of 25 × 100 mm and place them on the holder, piercing holes; between thin films insert a mesh or glass rods. Containers: cut from the walls specimens of about 1 dm², measure the dimensions to 1 mm and calculate the area of contact with the food to 0.01 dm².

3. Exposure

   Place the specimens on the holders in the glass tubes, pour in a measured volume of the simulant (a 100 ml cylinder) so that they are completely immersed and separated, close them and put them into a drying oven, an incubator or a refrigerator for the time of the test at the set temperature (method A) or heat them under reflux (method B).

   ⏱ Time: for example 10 days • 🌡 Temperature: for example 40 °C

4. Reagent blank

   In parallel subject the simulant itself (and possibly the holders without specimens) to the same conditions, and then evaporate and dry it like the specimens; the residue constitutes the blank (mb).

5. Evaporation

   After the exposure take the specimens out, and transfer the simulant from each specimen into an evaporating dish previously dried to constant mass; evaporate to dryness on a steam bath, a hotplate or in an evaporator.

6. Drying and weighing

   Dry the residue in a drying oven to constant mass, cool it in a desiccator and weigh it to the nearest 0.1 mg (ma); the evaporating dishes must show a constancy of mass of ±0.5 mg.

7. Calculation

   M = (ma − mb)·1000/S [mg/dm²] for every specimen; give the mean of three determinations. Where the area of contact differs from that in the test, convert the result into mg/kg of food according to EN 1186-1 (the ratio of the area to the mass of the food).

8. Assessment and test report

   Compare with the limit of 10 mg/dm² (60 mg/kg) taking into account the analytical tolerance of 2 mg/dm² for aqueous simulants; give the simulant, the conditions, the method (the part of the standard), the number of specimens, the result and the identification of the article. Articles for repeated use: three successive exposures of the same specimen, the assessment after the third.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• A scalpel and a knife when cutting out the specimens — cut on a board, away from the fingers
• The evaporation of 3 % acetic acid and of ethanol on a steam bath — under a fume hood, ethanol is flammable
• Hot evaporating dishes and a drying oven at 105–110 °C — tongs, thermal gloves, cooling in a desiccator
• Dilute nitric acid for cleaning the steel holders — goggles, gloves, a fume hood

Frequently asked questions