Regulation and use of metals as food contact materials

In general, the existing regulation of metal packaging covers the metallic and non-metallic components of the package separately. In the EU, where there is currently no harmonised specific regulation of metal foodstuff packaging, all components are covered primarily by the Framework Regulation (1935/2004) but it is expected that when harmonised legislation is extended to metal foodstuff packaging, metallic and non-metallic components will be treated separately. In the absence of harmonised EU specific regulation, compliance of metal foodstuff packaging is managed by a combination of national member state legislation and industry risk assessments.

11.2.1 State of current regulation of metals

Under most regulatory systems, metals are considered under food contaminant regulations rather than FCM regulations. Codex Alimentarius provides international guidance on acceptable limits for metals in foods. In addition, there are some national and EU limits and the Council of Europe has produced a guidance document on metals and alloys used as FCM (CoE 2001). The metals of relevance to metal foodstuff packaging are iron, tin, aluminium, chromium, and lead.

Iron

Iron is the major constituent of steel which is used either as tinplate or electro chromium coated steel (ECCS). However, the steel surface is always protected by a layer of tin and/or a protective organic coating. Iron is not controlled by specific regulatory limits although the joint FAO/WHO expert committee on food additives (JECFA) has established a provisional maximum tolerable daily intake (PMTDI) at 0.8 milligrams per kilogram bodyweight (mgkg-1 bw). Given the strong taint that iron imparts to foodstuffs, this limit is unlikely to be exceeded through the use of steel in foodstuff packaging. Iron migration from metal foodstuff packaging is monitored by industry during qualification testing because of the risk of tainting and because iron dissolution could indicate corrosion of the substrate leading to potential loss of can integrity. Standards exist for food packaging grades of tinplate (EN 10333), and ECCS (EN 10335).

Tin-coated steel (tinplate) is widely used in metal foodstuff packaging and is manufactured by electrochemical deposition. Levels of tin coating vary between 2.8 and 15.4 gm-2 depending on the application. It is usually covered by a protective organic coating although for dry foods and certain specific wet foods, the plain tinplate surface may be used without a coating. In the case of wet foodstuffs in contact with uncoated tinplate, a level of tin dissolution is inevitable and limits (statutory or recommended) are in place in most countries. In the EU, tin is covered by regulation No 242/2004 which limits levels to 200 mg kg-1 for canned food other than beverage, 100 mg kg-1 for beverages and 50 mg kg-1 for foodstuffs specifically marketed for infants. Most non-EU countries use the Codex Alimentarius limits of 250 mg kg-1 for solid foods and 150 mg kg-1 for liquid foods. However, the Codex limits are currently under review. Tin migration is only an issue where internal protective coatings are not used, although in practice, the EU limits will not be exceeded within the stated shelf life if appropriate foods are packed under good canning practice. It is important for the filler to control residual oxygen and oxidising contaminants, the presence of which control tin dissolution. Tin migration is monitored by industry during qualification testing to ensure that the controls are working correctly. Codex Alimentarius has published guidelines on the prevention and reduction of tin contamination in canned food (Codex 2005).

Aluminium

Aluminium cans, ends and closures are always covered with a protective organic coating which reduces aluminium migration to typically below 1 mg kg-1. Aluminium as a component of foodstuff packaging is not controlled by specific regulatory limits. However, EU Directive 98/83/EC on the quality of water intended for human consumption gives a standard value of 0.2 mg kg-1, as a compromise between the practical use of aluminium salts in drinking water treatment and discoloration of distributed water. It is a limit that represents good practice and is not a safety limit. Aluminium migration is monitored by industry during qualification testing in order to comply with limits imposed by specific foodstuff fillers, and also because aluminium dissolution could indicate corrosion of the substrate leading to potential loss of package integrity. A standard exists for a food packaging grade of aluminium (EN 602).

Chromium

Chromium is used at very low levels as a passivation coating for tinplate and at higher levels for ECCS. It may also be used to treat aluminium surfaces. The process ensures that the only species present are Cr0 and CrIII and not CrVI which is the toxicologically important species. Chromium in food is not generally regulated (there is a World Health Organisation (WHO) limit of 0.025 mg l-1 for drinking water). The level of migration from uncoated tinplate cans (the only metal foodstuff packaging where migration is likely to occur) is negligible and not considered to be of concern. Future change in environmental legislation is encouraging work on alternative passivation systems.

Lead

Lead has not been intentionally used in the manufacture of metal FCM for many years. Before welded 'three piece' cans became widespread, the side seams were commonly soldered with a lead based solder, a practice which is now virtually eliminated. However, it is not possible to obtain tin with zero lead contamination as the elements coexist in the ore. As a consequence, the tin content of tinplate will always contain traces of lead. Lead contamination of food is regulated in most countries with different levels for different foodstuffs (e.g. EU regulation No 466/2001) with limits typically in the range of 0.02 to 0.1 mg kg-1. The level of lead in the tin coating of tinplate is controlled by the tinplate specification, which in the past has allowed a maximum 500 mg kg-1 lead in the tin. At this level, in practice, lead limits in food should not be exceeded due to migration from metal foodstuff packaging. However, as a matter of due diligence, industry action in Europe and the USA is reducing the maximum level of lead in the tin coating of tinplate for food packaging to 100 mg kg-1 as defined in European Standard EN 10333.

11.2.2 State of current regulation of coatings

The regulation of food contact coatings on metal FCMs varies around the world.

The USA has a comprehensive and widely recognised regulatory system that specifically covers polymeric and resinous coatings under FDA CFR21 175.300 which lists authorised starting substances and lays down test conditions and migration limits. Globally, the great majority of coatings are formulated to be compliant with 175.300 and this is an important element of demonstrating the safety of coated metal foodstuff packaging even in the EU where 175.300 is not specifically recognised.

In the EU, harmonised regulations specific to coatings on metal have not yet been developed. However, the Framework Regulation 1935/2004 applies to all packaging types as do substance specific measures such as the 'Epoxy' Regulation 1895/2005 and the Vinyl Chloride Monomer (VCM) Directive 78/142/EEC. Compliance with these measures is essential, and whilst it is clear what needs to be achieved for compliance with the substance specific measures, the Framework Regulation, and in particular the key Article 3 gives no guidance on how compliance may be demonstrated. In the absence of harmonised legislation, EU national member state regulations, where they exist, may be used to demonstrate compliance with the Framework Regulation. The Dutch Verpakkingen- en Gebruiksartikelenbesluit (Hoofdstuk X) is the most comprehensive and has a positive list of permitted starting substances that is also used in other EU member states as a means of demonstrating compliance.

Other EU member states with legislation covering at least some aspects of coated metal FCM include France, Belgium and Greece. In addition to national member state legislation, reference to the CoE Resolution on Surface Coatings AP (2004) 1, together with published opinions of the Scientific Committee on Food/European Food Safety Authority (SCF/EFSA) and EU legislation that does not include coatings within its scope (such as Directive 2002/72/ EC on plastics food contact materials and articles) may be used in demonstrating compliance. In the case of thermoplastic polymer coated metal, the thermoplastic layer may, in most cases, be able to be fully compliant with the provisions of 2002/72/EC. However the more generally used thermoset coatings are more complex and can not generally be formulated using only substances authorised in 2002/72/EC. As can be seen, there is no clear path to demonstration of compliance for coated metal foodstuff packaging in the EU at present, and it is hoped that harmonised EU legislation in this area will be developed soon.

CoE Resolution on surface coatings AP (2004) 1

Although it has no legal status, this recently revised Resolution consists of a framework with technical appendices. It also includes comprehensive inventory lists of monomers and additives, all of which have some national member state or USA authorisation. The lists are divided into those which are already fully evaluated and included in the SCF/EFSA lists 0-4 and those which have not yet been fully evaluated by SCF/EFSA. This latter category is time limited with a deadline of five years from adoption of the Resolution by which time they must have been fully evaluated. There are still some outstanding issues with this Resolution that need to be addressed but it will be a useful reference in demonstrating compliance in the period before the EU is able to fully include surface coatings in its legislative framework.

11.2.3 State of current regulation of can end sealants

Can end sealants are based on natural or more usually synthetic rubber/latex with additives to give them the particular properties of adhesion, elasticity, temperature resistance and resistance to components of foods and beverages whilst ensuring an enduring hermetic seal. Under USA legislation they are specifically covered under FDA CFR21 175.300(xxxi) listing authorised starting substances. As with coatings, these materials are not yet covered under specific EU harmonised legislation so member state legislation may be used to show compliance. In particular the Dutch legislation has a section specifically covering can end sealants (Verpakkingen- en Gebruiksartikelenbesluit - Hoofdstuk IVf). The German recommendations of the BfR may also be useful for showing compliance. A CoE Resolution on Rubber and Elastomers AP (2004) 4 has been published but is not yet complete. In its finished form, it should be useful as a further reference for demonstrating safety and compliance of can end sealants.

11.2.4 State of current regulation of closure gaskets

These materials are fully regulated in the USA under FDA CFR21 177.1210 (Closures with sealing gaskets for food containers) which lists authorised starting substances and lays down test conditions and migration limits but they are not yet covered by harmonised EU legislation. As discussed earlier, these closures fall into two main types - vacuum closures for foodstuffs and non-vacuum closures for beverages. It has become clear that the nature of the gasket materials used for vacuum closures (PVC plastisols) can lead to significant levels of plasticiser migration when use in contact with fatty foods under sterilisation/pasteurisation conditions. The gaskets in vacuum closures are not free standing components but are flowed in place and fused in situ forming a soft sealing coating around the sealing surface. It is not clear to what extent such materials are within the scope of EU Directive 2002/72/EC which does not apply to multi material multi layer packaging but the European Commission are drafting a 'restrictions' Regulation that should clarify the position. With this measure it should be clear what these closures should comply with but the details were not finalised at the time of writing.

11.2.5 Management of food safety in the EU in the absence of harmonised legislation

It will be clear from the above sections that the current lack of harmonised EU legislation means that there is no single straightforward way to show compliance for most components of metal foodstuff packaging. The main measure which must be complied with is the Framework Regulation 1935/ 2004, Article 3 of which states that materials and articles should not transfer their constituents to food at levels which could: (i) endanger human health;

(ii) bring about an unacceptable change in the composition of the food; or

(iii) bring about a deterioration in the organoleptic characteristics thereof. The end-point of this requirement is clear but no guidance is given as to how to arrive at that end-point. This results in manufacturers and users of metal foodstuff packaging having to undertake their own risk assessments and compile justifications for compliance based on other existing legislation, recommendations and guidance. This leads to a range of approaches being adopted and a lack of clarity for all sectors in the chain including the regulatory and control authorities. It is for this reason that the metal foodstuff packaging industry chain is working proactively to help develop and promote harmonised legislation in this area.

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Responses

  • semere
    Why iron metal not use in food packaging?
    7 years ago

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