Plastic contact

Analysis of substances migrating from food contact plastics is possible at very low levels in real foods. Volatile species are the easiest to determine. 

Apart from routine quality control actions, additive analysis is often called upon in relation to testing additive effectiveness as well as in connection with food packaging and medical plastics, where the identities and levels of potentially toxic substances must be accurately known and controlled. Food contact plastics are regulated by maximum concentrations allowable in the plastic, which applies to residual monomers and processing aids as well as additives [64-66]. Analytical measurements provide not only a method of quality control but also a means of establishing the loss of stabilisers as a function of material processing and product ageing. 

For standard or proprietary polymer additive blends there is the need for analytical certification of the components. Blend technology has been developed for two- to six-component polymer additive blend systems, with certified analytical results [81]. Finally, there exist physical collections of reference additive samples, both public [82] and proprietary. The Dutch Food Inspection Service reference collection comprises 100 of the most important additives used in food contact plastics [83-85]. Reference compounds of a broad range of additives used in commercial plastics and rubber formulations are generally also available from the major additive manufacturers. These additive samples can be used as reference or calibration standards for chromatographic or spectroscopic analysis. DSM Plastics Reference Collection of Additives comprises over 1400 samples. 

Table 5.18 Main functional classes from the EEC inventory of additives intended for use in Food Contact Plastics Materials (Commission of the European Communities, 1991) [222]...

Sidwell and Zondervan [10] used LC-MS with APCI detection for the identification and quantification of extractable antioxidants from food-contact plastic materials. Identification is based on the presence of the molecular ion (M + FI)+, (M—H) , other key ions or on further ion breakdown (MSn) transitions. The following antioxidant/stabiliser types were examined hindered phenols,... 

Table 10 EN 13130 standard methods for the quantification of extractable monomers used for food-contact plastics...

This presentation discusses current EU chemical legislation and examines the shortcomings of some of the regulations in place with respect to dangerous chemicals. The Commission White Paper is discussed, and in particular, the REACH system which involves the registration, evaluation and authorisation of chemicals used in food-contact applications. The impact of the REACH system on food-contact plastic manufacturers is examined, with respect to suppliers of monomers and additives, plastic manufacturers, converters and packagers. 

Although European Directives have been issued on legislative requirements for food contact plastics, European harmonisation of regulations for rubber or thermoplastic elastomers used in contact with food is yet... 

A comprehensive study, performed in the USA by DCMA has shown, that the metal impurity in organic pigments is markedly below legal standards [8]. Recently ETAD (see footnote p. 590) and VdMi (German Association of inorganic pigments) have published a review on colorants for food contact plastics [9],... 

Colorants for Food Contact Plastics, ETAD/VdMi, 2002. 

Kawamura, Y., Ogawa, Y., Nishimura, T., Kikuchi, Y., Nishikawa, J., Nishihara, T., and Tanamoto, K., 2003, Estrogenic activities of UV stabilizers used in food contact plastics and benzophenone derivatives tested by the yeast two-hybrid assay, J. Health Sci. 49 205-212. 

The plastics industry is mainly concerned with the Bureau of Foods which conducts research and develops standards on the composition, quality, nutrition, and safety of foods, food additives, colors and cosmetics, and conducts research designed to improve the detection, prevention, and control of contamination. The FDA is concerned about indirect additives. Indirect additives are those substances capable of migrating into food from contacting plastic materials. Extensive tests are carried out by the FDA before issuing safety clearance to any plastic... 

The quasi-static acquisition and interpretation of the force-distance curves is straightforward for elastic materials. The information is generally incomplete and less reproducible for polymers which demonstrate viscoelastic contact, plastic deformation, and ploughing type friction. Moreover, they exhibit a wide spectrum of relaxation times from 105 to 109 Hz [121]. 

At the time of writing, DEHA has not yet been included in the EU positive list of additives used to make food contact plastics. With an established TDI of 0.3 mg/kg bw/day and using the normal conservative assumptions of 1 kg food consumed daily and a 60 kg bw, this TDI would give a specific migration limit of 18 mg DEHA per kg food or food simulant. It must be recognised that non-compliance with a migration limit of 18 mg/kg based on this convention does not necessarily mean that the TDI could be exceeded. It seems unlikely that DEHA will be listed until the issue of food consumption factors is resolved. 

Allen, D.W., Brooks, J.S., Unwin, J. and McGuinness, J.D. (1985) Gamma-irradiation of food contact plastics. Chem. Ind. London 15, 524. 

Kwapong, O. Y., and Hotchkiss, J. H. (1987). Comparative sorption of aroma compounds by polyethylene and ionomer food-contact plastics. /. Food Sci. 52, 761-763. (see also p. 785). 

Three different approaches have been presented for estimating the partitioning of solutes between plastics and liquids. In the context of evaluating the output from these different approaches it is also useful to define the expected experimental ranges and limits for partition coefficients based on the solutes, plastic and contacting liquid phases involved. Table 4-9 shows approximate upper and lower limits for partition coefficients one may normally encounter in plastic/food systems based on the polarities of the solutes, plastics and foods. The table also gives approximate ranges of partition coefficient values for various solutes between typical food contact plastics and liquid phases. 

To further illustrate the possible experimental ranges of partition coefficients, examples of experimentally determined partition coefficient ranges are given below. In Table 4-10 data for BHT partitioned between polypropylene and different food and food simulants at 40 °C and in Table 4-11 for d-limonene partitioned between LDPE and various foods and food simulants are shown. The partition coefficient values in these tables are representative examples of the ranges one can expect with polyolefins which are the most common food contact plastics. 

Kwapong, O.Y., Hotchkiss, J.H. Comparative Sorption of Aroma Compounds by Polyethylene and Ionomer Food-Contact Plastics. Journal of Food Science. 1987,52(3) 761-785. 

Butadiene, CH2=CH-CH=CH2 (CAS No. 106-99-0 PM/Ref. No. 13630) is commonly copolymerized with styrene and acrylonitrile to make ABS or BS food contact plastics (for applications see acrylonitrile). Butadiene is a suspected carcinogen with extreme volatility (bp -4.5 °C) and low water solubility. This makes it very difficult to handle migration and calibration samples where the matrix is of highly aqueous character such as the aqueous food simulants. 

Tice P and Cooper I, 1997, Rationalizing the testing of food contact plastics. In R. Ashby, I. Cooper, S. Harvey and P. Tice Food Packaging Migration and Legislation. Pira International, Leatherhead 1997 (Chapter 5, p 155). 

Biles. J.E., McNeal, T.P., Begley, T.H., and Hollifield, H.C., 1997, Determination of Bisphenol-A in Reusable Polycarbonate Food-Contact Plastics and Migration to Food Simulating Liquids. J. of Agric. Food Chem. Vol. 45, No. 9,3541-3544. 

Another application of ICP-MS in the area of food safety is the evaluation of food contact materials. Q [86] and TOF [87] mass spectrometers have been employed in the compositional analysis of paper and board material intended for food contact. Studies on the migration of metals from food contact plastics using food simulants and ICP-MS detection have also been reported. One of them showed how to analyze different simulants without the need of any time-consuming preparation, that is, aqueous acetic acid (3 percent w/v) directly, aqueous ethanol (15 percent v/v) after proper dilution, the olive oil simulant following emulsion preparation by means of tetralin and Triton X-100 [88]. 

How, you may ask, can the FDA be so irresponsible as to approve for use in food contact applications a substance that is a suspected carcinogen A bit of common sense, often a rarity in environmental matters, prevailed in this situation. The FDA recognized that the only way cobalt compounds are carcinogenic, if indeed they are at all, is via the respiratory route. Since it is not reasonable to anticipate that food contact plastics will be inhaled, and since there is no other discernible hazard, the FDA has approved the use of these colorants. 

Polarized incident radiation is necessary also when anisotropic samples such as stretched polymers (Flournoy and Schaffers, 1966) are studied. Crystals may require immersion in order to assure the necessary optical contact. Plastic selenium has proved to be useful (Gottlieb, 1968). In this way the three different infrared spectra of an orthorhombic single crystal were obtained which are shown in Fig. 2.7-10 (cf. Sec. 2.7.6.4 Schrader et al., 1971). The orientation of the optical axis or axes with respect to the experimental frame is crucial. For the evaluation the field components have to be considered separately in order to interprete the response of the oriented transitions correctly. Addressing different components equivalently is achieved by rotating the sample together with the internal reflexion element with respect to the beam (Hobbs et al., 1983 Palm, 1994). 

BEGLEY T, CASTLE L, FEIGENBAUM A, FRANZ R, HINRICHS K, LICKLY T, MERCEA P, MILANA M, O BRIEN A, REBRE s, RIJK R and PiRiNGER o (2005), Evaluation of migration models that might be used in support of regulations for food contact plastics . Food Additives and Contaminants, 22(1), 73-90. 

Harmonisation of national legislation on the substances used in food contact plastics was started with monomers as these are reactive substances and thus of primary importance as regards any potential health risk. Monomers and other starting substances are fully harmonised at Community level. This means that only the monomers listed in the specific Community legislation can be used in food contact plastics. An exemption exists for plastic coatings, adhesives and epoxy resins. Monomers which are used only in their manufacture are not listed in the Community lists. 

In a second step, the harmonisation of additives used in plastic food contact materials was started. However, this step is not yet finished Therefore, additives listed both in the Community legislation and in national legislation can be used in food contact plastics (for national lists see section 3.7). It is foreseen that harmonisation on additives will be finalised by 2007. Until 31 December 2006 all parties interested in additives authorised at national level have to supply EFSA with a valid application for evaluation of this additive. Only additives for which a valid application has been supplied may continue to be used according to national audorisation until evaluation is finalised by EFSA and a decision on authorisation is taken by the European Commission. The Community list on additives contains those additives that are used solely in plastics and those used both in plastics and coatings. However, it does not contain additives used only in plastic coatings, adhesives and epoxy resins. 

Although it is specific to these substances, this legislation has been the first to explicitly set out any rules for coatings and adhesives and those plastics not within scope of the rules on food contact plastics. This last point arises from the fact that the legislation covers all plastic materials and articles, not just those within the scope of Directive 2002/72/EC, as amended. 

The name of the supplier and the type or grade of the starting material. The place and date of production, batch number or another equivalent identification number that will unequivocally identify the starting material. In the specific case of starting materials for food contact plastics, documentation of compliance with details of the legislation with which they are complying. 

Types of food contact plastics and their components... 

The raw materials used for manufacturing food contact plastic materials are ... 

Other substances may be present in food contact plastics that were not originally intended to be present in the finished material or article, but arise from reactions during polymerisation or processing. Or they may be present as... 

Another class of secondary antioxidants used in food contact plastics is thioether. The most common examples used in polypropylene, polystyrene and PVC are thiodipropanoic acid, didodecyl ester (DLTDP) and thiodipropanoic acid, dioctadecyl ester (DSTDP). Thioethers react with hydroperoxides to form sulphoxides as shown in Fig. 10.8. 

Catalysts are currently not covered specifically by EU directives on food contact plastics. They tend to decompose during the polymerisation process. Again, the degradation products are often predictable and may sometimes be found in the finished food contact material. However, catalysts are usually present at low levels and the degradation products are often volatile. For example, the common catalyst t-butyl perbenzoate may decompose to give benzene when used in some thermoset polymers.Tert-butyl peroxide is used as a catalyst in certain polymers and will decompose to give tert-butanol. 

---