Testing plastics materials for compliance with EU directives

EU legislation covering plastics food contact materials is well advanced with a positive list for monomers complete and a positive list for additives near completion. Decisions on how other substances used in plastics, such as aids to polymerisation and colourants are to be regulated, if at all, have yet to be made. Plastics used in contact with food must comply with the Framework Regulation,1 which lays down the basic rules:

Materials and articles in contact with food shall be manufactured in compliance with good manufacturing practice so that, under normal or foreseeable conditions of use, they do not transfer their constituents to food in quantities which could:

• endanger human health

• bring about an unacceptable change in the composition of the food

• bring about a deterioration of the organoleptic characteristics thereof.

Plastics food contact materials and articles should comply with Directive 2002/72/EC2 and its amendments that include:

• an overall migration limit (OML)

• specific migration limits (SMLs) on monomers

• specific migration limits (SMLs) on additives

• compositional limits (QMs) on some monomers.

Demonstration of compliance with any of these restrictions, where applicable, is the main responsibility of the converter who makes the finished plastics article. However, the food packer or retailer who is at the 'sharp end' of any enforcement and the polymer manufacturer, who should ensure that the polymer granules comprise only authorised substances, also have responsibilities to fulfil. The British Plastics Federation 'Guide'3 provides extensive guidance on the responsibilities of each link in the chain and other related issues such as Good Manufacturing Practice and frequency of retesting. The 'Guide' proposes that if the test result is between 0-33% of the limit then annual retesting is sufficient. If the results are between 33-66% of the limit then an immediate retest should be carried out to ensure that the results are repeatedly within the band or lower. If confirmed then annual retesting may be sufficient. If the test result is greater than 66% of the limit then there should be an immediate retest twice on different samples followed by sufficient testing to ensure that the results are repeatedly lower than the limit. Consideration should be given to batch-by-batch testing to build up a statistical case for compliance. In the UK it is important to demonstrate due diligence and not rely entirely on warranty and statements from suppliers. Figure 10.1 illustrates the main responsibilities.

Demonstration of compliance with specific migration limits may be accomplished by two simple procedures that should be considered first before any testing is conducted.

Fig. 10.1 Summary of responsibilities of food packaging supply chain.

1. Determination of levels of residual substances and calculation of 100% mass transfer to food. Measurement of levels is usually needed for monomers, but in the case of additives this can be the level added to the polymer.

2. Use of a 'generally recognised' migration model based upon diffusion theory, such as MIGRATEST Lite® (see Chapter 8). There are some cases where migration cannot be predicted by this approach including substances that are ionic, or those that bloom to the surface of the polymer or are not homogeneously distributed, or some polymers such as plasticised PVC.

However, where these simple approaches are not appropriate, or the calculated values exceed SMLs then migration tests are conducted, normally using food simulants (see Chapter 5).

10.2.1 Test conditions

The migration tests that are performed on food contact materials need to be done using appropriate test conditions that properly cover the conditions of use (see also Chapter 5). This is most important and needs knowledge about how the food is packed, processed and stored. Selection of the correct temperature for a test is particularly important. The relationship between temperature and migration of a substance generally can be described by the Arrhenius equation. In some cases the temperature in use is not precisely known. For example for PVC stretch film for home use compliance tests are usually carried out for ten days at 20 °C with fat. This is a reasonable compromise between ten days at 40 °C (shelf storage) which is judged to be too severe and ten days at 5 °C (refrigerated storage) which is not severe enough. The test conditions for evaluation of compliance against food contact legislation are laid out in Directive 97/48/EC and amendments.4

Where storage under ambient or chilled temperatures is intended for the foodstuff, accelerated tests are carried out. For example, ten days at 40 °C covers ambient storage. For a combination of time and temperatures a combination of test conditions is used. In some cases carrying out only the most severe test is allowed. For example two hours at 175 °C to cover oven cooking would also cover ambient storage. To cover all anticipated conditions of use, test conditions of two hours at 175 °C with olive oil, and reflux conditions for four hours are used with aqueous simulants. Some examples of test conditions are given in Table 10.1.

It should be noted that items intended for repeated use, such as the spatula and beer mug, should be tested according to the guidelines given in the Directive 2002/72/EC where the test is repeated three times on the same test piece, using fresh simulant on each occasion. Compliance is then judged based upon the result obtained on the third test. When the temperature of the food is not known or cannot be judged, for example, with microwaveable

Table 10.1 Selection of test conditions

Food contact

Processing/conditions of use

Test conditions


PET bottle

Aseptic filling and shelf storage

10 days at 40 °C

PP pouch

Retort sterilisation plus shelf

2 h at 121 °C plus 10


days at 40°C

PET ovenable tray

Refrigerated storage plus

1 h at 175 °C (fat)

cooking in a conventional oven

4 h reflux (aqueous)

PS vending cup

'Hot fill'

2 hours at 70 °C


Short exposure at room

30 minutes at 40 °C or

beer mug


30 minutes at 20 °C


Mixing/dispensing hot food

30 min at 175 °C (fat) 2 h at reflux (aqueous)

VC/VA copolymer

Storage 1 day ambient

24 hours at 40 °C

sandwich pack

Soup pouch

Refrigerated storage plus

30 min at 130 °C (fat)

microwave reheat

30 min at 100 °C (aqueous)

Glass jar with

Sterilised plus ambient storage

2 h at 121 °C plus 10

twist-off cap

days at 40 °C

food, the temperature of the food/plastic interface can be measured by use of thermocouples or infra-red thermography.

10.2.2 Overall migration testing

The EU overall migration limit was originally introduced to minimise the number of SMLs, so that substances with a Tolerable or Acceptable Daily Intake of 1 mg/kg bodyweight or greater need not be given a SML because they would automatically exceed the Overall Migration Limit (60 mg/kg or 10 mg/dm2). In practice, this does not hold true for volatile substances as these are lost in the overall migration test procedures. Tests are carried out using food simulants and the test methods are EN Standards 1186 Materials and articles in contact with foodstuffs - Plastics - Parts 1-15, shown below. They are available in the UK from the British Standards Institution, 389 Chiswick High Rd, London W4 4AL.

Part 1 Guide to selection of conditions and test methods for overall migration.

Part 2 Test methods for overall migration into olive oil by total immersion. Part 3 Test methods for overall migration into aqueous food simulants by total immersion.

Part 4 Test methods for overall migration into olive oil by cell. Part 5 Test methods for overall migration into aqueous food simulants by cell.

Part 6 Test methods for overall migration into olive oil using a pouch. Part 7 Test methods for overall migration into aqueous food simulants using a pouch.

Part 8 Test methods for overall migration into olive oil by article filling. Part 9 Test methods for overall migration into aqueous food simulants by article filling.

Part 10 Test methods for overall migration into olive oil (modified method for use in cases where incomplete extraction of olive oil occurs). Part 11 Test methods for overall migration into mixtures of 14C-labelled synthetic triglycerides. Part 12 Test methods for overall migration at low temperatures. Part 13 Test methods for overall migration at high temperatures. Part 14 Test methods for 'substitute tests' for overall migration from plastics intended to come into contact with fatty foodstuffs using test media iso-octane and 95% ethanol. Part 15 Alternative test methods for migration into fatty food simulants by rapid extraction into iso-octane and 95% ethanol.

Part 1 of EN1186 describes the basic rules for the following: choosing the most appropriate mode of test; how the plastic specimen is brought into contact with the food simulant (e.g. by total immersion, in a cell or pouch, filling a plastic article); the most appropriate test conditions to use. After exposing test specimens to food simulants, the solvent and aqueous-based food simulants are evaporated to dryness and the residue accurately weighed. The aqueous Overall Migration (OM) test methods have been ring-trialled and a reproducibility of better than 2 mg/dm2 or 12 mg/kg achieved. Results are expressed in units of mg/dm2 except for containers and articles that can be filled with a volume less than 500 ml or greater than ten litres. Generally, very few plastics exceed the OM limit with aqueous food simulants, except for some biodegradable polymers. Occasionally formulations containing calcium carbonate as a filler will give rise to high values using 3% acetic acid.

With the OM test with olive oil, or an alternative fat simulant, such as sunflower oil or HB307, it is the weight loss on the plastic test pieces that is measured. To take into account the quantity of fat absorbed by the test pieces during the exposure, the fat is extracted using a solvent and determined separately by gas chromatography. In ring trials a reproducibility of better than 3 mg/dm2 or 18 mg/kg was achieved. Instances when plastics exceed the OM test limit with olive oil are mainly older formulation PVC 'stretch films' that contain plasticisers, or polyolefins tested at temperatures around their maximum useful temperature. In the case of PVC stretch films, these have been largely reformulated replacing a significant percentage of the monomeric plasticiser, di-(2-ethylhexyl) adipate (DEHA), with polymeric adipates that have less propensity for migration. Even the newer style PVC films are not suited to wrapping pure fats and oils or margarine where the reduction factor of 1 or 2 will not bring down the olive oil test result to below the OM limit of 10 mg/dm2.

10.2.3 Specific migration testing

Directive 2002/72/EC contains a positive list of monomers, therefore food contact plastics can be made using only listed substances. Some substances are subject to limitations in the form of specific migration limits (SMLs) or restrictions on the maximum permitted residual concentration of a substance in the finished product (QM or QMA) (see also Chapter 5). To test for compliance with SMLs, migration tests can be carried out using food simulants or foods. The test methods that have been validated for food simulants are EN Standards 13130 Parts 1-8. Part 1 of EN 13130 describes ways of conducting the specific migration test by total immersion, cell, article fill or pouch. Specific migration tests for volatile substances require the use of a sealed cell to mimic the worst-case situation. A typical cell is shown in Fig. 10.2. Listed below are the parts of EN 13130/ Monomer test methods for plastics materials and articles intended to come into contact with foodstuffs. They are available in the UK from the British Standards Institution, 389 Chiswick High Rd, London W4 4AL.

Part 1 Guide to the test methods for specific migration of substances from plastics into foods and food simulants and the determination of

Fig. 10.2 Glass migration cell for one-sided contact (courtesy FABES, Munich).

substances in plastics and the selection of conditions of exposure to food simulants.

Part 2 Determination of terephthalic acid in food simulants (SML = 7.5 mg/kg).

Part 3 Determination of acrylonitrile in food and food simulants (SML =

not detectable, DL = 0.02 mg/kg). Part 4 Determination of 1,3-butadiene in plastics (QM = 1 mg/kg). Part 5 Determination of vinylidene chloride in food simulants (SML = not detectable, DL = 0.05 mg/kg). Part 6 Determination of vinylidene chloride in plastics (QM = 5 mg/kg). Part 7 Determination of monoethylene glycol and diethylene glycol food simulants (SML(T) = 30 mg/kg). Part 8 Determination of isocyanates in plastics (QM = 1 mg/kg).

SML = specific migration limit in food or food simulant.

QM = maximum permitted quantity of the 'residual' substance in the material or article.

DL = detection limit of the method of analysis.

A further 20 monomer test methods were developed in the EU funded BCR Project.5 The number of monomer test methods published in the report was 35. This was reduced to 20 for the new work items by removing a method for BADGE (bisphenol A diglycidyl ether). This was covered separately by Task/Working Group 8. The number was also reduced by consolidating similar methods. The substances covered by the 20 methods are given below.

They were published as Technical Specifications (TS) in February 2005. As Technical Specifications these methods will be required to be reviewed every two years.

1. acetic acid, vinyl ester (vinyl acetate).

2. acrylamide.

3. 11-aminoundecanoic acid.

4. 1,3-benzenedimethaneamine.

5. 2,2-bis(4-hydroxyphenyl) propane.

6. 3,3-bis(3-methyl-4-hydroxyphenyl)-2-indolinone.

7. butadiene.

8. caprolactam and caprolactam salt.

9. carbonyl chloride.

10. 1,2-dihydroxybenzene, 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 4,4'-dihydroxybenzophenone and 4,4'-dihydroxybiphenyl.

11. dimethylaminoethanol.

12. epichlorohydrin.

13. ethylenediamine and hexamethylenediamine.

14. ethylene oxide and propylene oxide.

15. formaldehyde and hexamethylenetetramine.

16. maleic acid and maleic anhydride.

17. 4-methyl-pentene.

18. 1-octene and tetrahydrofuran.

19. 2,4,6-triamino-1,3,5-triazine.

20. 1,1,1-trimethylopropane.

There is no analytical method available for many substances and in these cases it is necessary to develop a method with 'acceptable performance'. In the first instance, where no information exists on the stability of the substance to be measured, then it is a good idea to carry out a recovery test. This is done by adding the substance at an appropriate level to the food simulants and measuring the amount of substance remaining after the proposed test conditions have been applied. It is best carried out in the same cell as the proposed migration tests. A poor recovery of, say, < 50% indicates the substance may be degrading or lost from the cell. In this situation it may be necessary to use a different cell or a different test medium to improve the recovery by use of a substitute test, for example, instead of olive oil. In some cases it may not be possible to improve the recovery and consideration should be given to measurement of the level in the polymer and migration modelling or measurement of the decomposition products.

For borderline cases where recoveries are outside of the analytical tolerance, at say 50-70%, it is arguable whether correction of the concentrations found in the migration test for the recovery is justified. But it can be viewed to be a 'worst case' and so in principle it is recommended. Losses may also occur due to insolubility of the substance in the food simulant or adsorption onto glass/metal surfaces and this should be investigated by rinsing the cell with a suitable solvent.

The document 'Note for Guidance'6 available on website www.efsa.eu.int provides guidance on provision of migration (and other) data for the authorisation of new substances for food contact application. In particular, method performance should be adequate at the given SML with data obtained on the precision and the limits of detection and quantitation. In the event that the SML is exceeded then confirmation of the level present is essential, preferably using mass spectrometry.

0 0

Post a comment