23.1 Introduction Food packaging is a still growing market. As a consequence, the demand to re-use post-consumer packaging materials grows as well. Recycling of packaging materials plays an increasing role in packaging, and numerous applications can already be found on the market. Ten or twenty years ago most post-consumer packaging waste was going into landfill sites or to incineration. Traditionally, only glass and paper/board were recycled into new applications. In the case of packaging plastics the situation is quite different. Only uncontaminated in-house production waste was collected, ground and recycled into the feedstream of the packaging production line without further decontamination. With increasing environmental demands, however, post-consumer plastics packaging materials have also been considered more and more for recycling into new packaging. A closed-loop recycling for packaging plastics is also supported by public pressure. The packaging and filling companies have to take responsibility for their packaging materials and environmental concerns. In many countries the consumer, government and the packaging companies want to have packaging materials with a more favourable ecobalance in the supermarkets. A more favourable ecobalance can be achieved with different approaches. One of these approaches is the re-use of recycled material in packaging. This development is driven by the recent strong increase in polyethylene terephthalate (PET) bottles used for soft drinks, water and other foodstuffs. 1 Today, many filling companies have decided to start using recycled plastics into their PET bottles in the near future. But recycling of packing plastics is also a question of recycling technology and collection of packaging waste. Today many countries have established 23 Recycling packaging materials R. Franz and F. Welle, Fraunhofer Institute for Process Engineering and Packaging, Germany collection systems for post-consumer packaging waste, like the green dot systems. Such country-wide collecting systems guarantee increasing recovery rates. Together with new developments of recycling systems and with increasing recycling capacity the way is open for some plastics for a high value recycling of packaging waste. Due to health concerns most of the recycled post-consumer plastics are going into less critical non-food applications, but in recent years there have also been efforts to recycle post-consumer plastics like PET into new food packaging applications. This changes the situation for some packaging plastics from an open-loop recycling of packaging plastics into a closed-loop recycling into new packaging materials. However, the recycling of post- consumer plastics into direct food contact application needs much more knowledge about contamination and migration than for non-food applications, in order to assess the risk to consumers’ health. Additionally a quality assurance system for post-consumer plastics should be established. 23.2 The recyclability of packaging plastics It is generally known that food contact materials are not completely inert and can interact with the filled product. 2 In particular, interactions between packaging plastics and organic chemicals deserve the highest interest in this context. Such interactions start with the time point of filling and continue during the regular usage phase of a package and even longer, in case a consumer ‘misuses’ the empty packaging by filling it with chemical formulations such as household cleaners, pesticide solutions, mineral oil or others. The extent of these interactions depends on the sorption properties and the diffusion behaviour which is specific to certain polymer types or individual plastics. These physical properties together with the contact conditions ultimately determine the potential risk of food contamination from recycled packaging plastics. In other words, taking only the polymer itself into consideration and not possible recycling technologies with their special cleaning efficiencies, etc., under given conditions the inertness of the polymer is the basic parameter which determines the possibility for closed-loop recycling of packaging plastics. The inertness of common packaging polymers decreases in the following sequence: Poly(ethylene naphthalate) (PEN), poly(ethylene terephthalate) (PET), rigid poly(vinyl chloride) (PVC) > polystyrene (PS) > high density polyethylene (HDPE), polypropylene (PP) > low density polyethylene (LDPE) In relation to this aspect, PEN, PET or rigid PVC do possess much more favourable material properties in comparison to other packaging plastics, such as polyolefins or polystyrene and are, therefore, from a migration related point of view much better suited for being reused in packaging applications. Polymers 498 Novel food packaging techniques like polystyrene and HDPE may also be introduced into closed loop recycling if the cleaning efficiency of the recycling process is high enough regarding the input concentrations of post-consumer substances. However, regarding consumers’ safety, the composition and concentration of typical substances in post-consumer plastics and the ability of the applied recycling process to remove all post-consumer substances to concentrations similar to virgin materials is of interest. The incoming concentration of post-consumer contaminants can be controlled off-line with laboratory equipment like gas chromatography or HPLC or online with detecting or sniffing devices. With help of online devices nearly a 100% control of the input materials can be established. Therefore the post- consumer material is much more under control and packaging materials with high concentrations of migratable substances, or misused bottles, can be rejected and the requirements on the cleaning efficiency of the recycling process are lower. The source control is therefore the crucial point regarding of the ‘worst- case’ scenario of the so-called challenge test (see Section 23.4.1). Recovery of packaging plastics into new packaging applications requires blending of recycled with virgin materials. In praxis today, the recyclate content of packaging materials varies from only a few per cent up to 50% recycled material in some packaging applications. Numerous studies have been carried out on the determination the material properties and the blending behaviour of recycled plastics. However, it is not the focus of this chapter to deal with blending of polymers but it needs to be stressed that the recycled material should be suitable for blending with virgin materials. Additionally, the mechanical properties of the recyclate should be not influenced in a negative way, so as to avoid potential consequences for the additive status of the recycled plastics. The average number of cycles is a function of the blend ratio and the number of recycling steps carried out. In practice the average number of cycles ranges from one to three. 3 Therefore, the material is not recycled many times and the problem of accumulation of degradation products is in most cases of no concern. An inherent problem of recycling, however, is the inhomogeneity of the recovered materials. Normally various polymer additives, lubricants, etc. are used by the different polymer manufacturers or converters in order to establish the desired properties of the packaging materials, and all different polymer additives are found as a mixture in the recyclate containing packages. Modern sorting technologies are able to provide input materials for recycling which are nearly 100% of one polymer type. Taking, in addition, the additive status into account will be a sophisticated challenge of future developments. Together with the inertness of the polymers this is one reason why recent closed-loop recycling efforts are focused on polymers which have low amounts of additives e.g. PET. However, as mentioned above, the question of recyclability is mainly influenced by the source control of the input material going into the recycling process. If the recovery system considers the manufacturer or the origin of the packaging materials, usually the additive status of the input feedstock is known. An example for this will be HDPE milk bottles collected by a deposit system (see Section 23.5.2). Recycling packaging materials 499 23.3 Improving the recyclability of plastic packaging 23.3.1 Source control The source control is the first and most important step in closed-loop recycling of packaging plastics. There must be efficient recovery or sorting processes which are able to control the input fraction going into a closed-loop recycling process. The feedstream material should have a minimum polymer type purity of 99%. Other polymers, which may interfere, have to be sorted out of the recycling stream. Also the first life of the packaging material is of interest. In general only packages previously filled with foodstuffs should be used as an input fraction for a closed-loop recycling process. However there are exceptions, e.g. for PET due to its high inertness the first packaging application is not so important. Two studies were undertaken 4,5 to determine the impact of PET materials formerly used for non-food applications. Both studies came to the same result, that due to the low diffusivity of PET packages from non-food applications could also be used as input material for bottle-to-bottle recycling. This underlines the favourite position of PET bottles for a closed loop recycling. It could be shown that deposit systems and recovery systems like curbside packaging collections with efficient sorting processes, are able to support input materials for high value recycling. However, as mentioned above, the higher the diffusivity of the polymer and, therefore, higher sorption of post-consumer substances the more important is the source control in order to reduce contamination with post-consumer substances or misused packages. The source control can be supplied by modern detecting or sniffing devices which are able to reduce the intake of undesired post-consumer substances into the recycling stream. 23.3.2 Contamination levels and frequency of misuse of recycled plastics Regarding the typical contamination of post-consumer plastics most published data are available for PET bottles and corresponding recyclates. Most of them have quantified or identified substances in post-consumer PET by using different methods. Sadler et al. 6,7 , published two studies containing data of contaminants in recycled PET. In the first study he pointed out that most compounds found in recycled PET come from PET starting materials, oligomers, flavour bases, label materials and compounds originating in base cups. Contaminants which do not fall into one of these categories are rare. In samples with high levels of contaminants the sum of all compounds was detected to be approximately 25 ppm. No single contaminant appears to be present in post-consumer PET above 1 ppm and all non-usual compounds in post-consumer PET were present below 0.1 ppm. In a second study the identity and origin of contaminants in food grade virgin and commercially washed post- consumer PET flakes were determined. A total of 18 samples of post-consumer recycled PET flakes was examined. In most cases, positive identification was possible, however, in few cases ambiguity resulted from the similarities in mass 500 Novel food packaging techniques spectra of closely related compounds. Compounds identified were classified into categories associated with their chemical nature or presumed origins, e.g. small and ethylene glycol related compounds (methanol, formic acid, acetaldehyde, acetic acid), flavour compounds (limonene), benzoic acid or related benzene dicarboxylic acid substances (benzoic and terephthalic acid and corresponding esters, benzaldehyde, phthalates), aliphatic hydrocarbons and acids as well as unexpected and miscellaneous compounds (Tinuvin, nicotine). Bayer 4 has analysed samples from five different recovery systems including PET containers from non-food applications. In these samples he identified 121 substances. The total concentration of all substances found in deposit material was 28.5 ppm. The corresponding concentrations of PET flakes coming from non-food applications were found to be 39 ppm. The key compounds identified were hexanal, benzaldehyde, limonene, methyl salicylate and 5-iso-propyl-2- methylphenol (the flavour compound carvacrol). In conventional washed flakes a maximum concentration of 18 ppm for limonene was determined. For PET flakes from non-food applications the major compound methyl salicylate was determined in a maximum concentration of 15.3 ppm. Additionally the material was analysed after a super-clean process. No peak could be detected in concentrations above the FDA threshold of regulation limit of 0.22 ppm. All three published studies mentioned above found no hints for misuse of post-consumer PET bottles e.g. for storage of household cleaners etc. This is most probably due to the fact that these studies are based only on very small amounts of different flake samples. From a statistical point of view flakes from misused bottles should be extremely rare due to high dilution with non-misused PET bottles. Therefore, these published studies are not able to detect the frequency of misuse in typical post-consumer PET flakes. In 2002 an EU project under the co-ordination of Fraunhofer IVV was finished. 8,9,10 Within this study 689 post-consumer PET flake samples from commercial washing plants were collected between 1997 and 2001. The samples are conventionally recycled deposit and curbside fractions collected in twelve European countries. In addition, 38 reprocessed pellet samples and 142 samples from super-clean recycling processes were collected. All samples were screened for post-consumer substances, and for hints of possible misuse of the PET bottles by the consumer, in order to get an overview of the quality of commercially recycled post-consumer PET. As a result the average concentrations in 689 PET flake samples for typical post-consumer compounds like limonene and acetaldehyde are 2.9 ppm and 18.6 ppm, respectively. A maximum concentration of approximately 20 ppm of limonene and 86 ppm for acetaldehyde could be determined, which is in close agreement with the above- mentioned studies. The impact of the recovery system and the country, where the post-consumer PET bottles were collected, on the nature and extent of adventitious contaminants was found not to be significant. However in three bottle flakes hints for a possible misuse of PET bottles e.g. for storage of household chemicals or fuels were found. From a statistical evaluation 0.03 to 0.04% of the PET bottles might be misused. Under consideration of the dilution Recycling packaging materials 501 of the PET flakes during washing and grinding with non-misused PET bottles average concentrations of 1.4 to 2.7 ppm for conspicuous substances from misused PET bottles were estimated from the experimental data. These concentrations can be considered as a basis for the design of challenge tests with respect to sufficiently high input concentrations of surrogates. The frequency of misuse was also detected by two other studies. Allen and Blakistone 11 indicate that hydrocarbon ‘sniffers’ for refillable PET bottles rejected between 0.3 and 1% of PET bottles as contaminated. The majority of these rejections came from PET containers with ‘exotic’ beverages and not from harmful contaminants. Therefore the part of misused bottles on the rejection in the ‘sniffer’ device is less than 0.3 to 1%. Bayer et al. 12 reported the frequency of misuse of PET bottles is one misused bottle out of 10 000 uncontaminated bottles. Both studies are in agreement with the results of the EU project. In conclusion for PET the predominating polymer unspecific contaminants are soft drink components where limonene plays a key role. PET unspecific contaminants such as phthalates are found far below 1 ppm. Misuse of PET bottles occurs only in a very low incidence and due to dilution with non- contaminated material the average concentration of substances originated from misuse are also in the lower ppm range. It should be noted here, that the given conclusions are only for PET bottles. If closed loop recycling of other packaging plastics is to be established similar studies on the input concentrations of post- consumer substances should be done. Comprehensive studies on the contamination of other polymers than PET are vary rare in the literature. Huber and Franz 13 investigated 21 reprocessed HDPE pellet samples from the bottle fraction of household waste collections from five different sources. Aim of the study was to investigate the quality of the recycled HDPE samples focusing on substances which are not present in virgin polymers. The samples are recycled with conventional washing and extruding steps without a further deep cleansing recycling process. They found that the post- consumer related substances in these different samples were the same. They identified 74 substances which occur in concentrations in the polymers above 0.5 ppm. The predominant species are ester from saturated fatty acids and phthalates, hydrocarbons, preservatives, monoterpenes and sesquiterpenes including their derivatives. Most of the substances are identified as constituents from personal hygiene products, cosmetics and cleaning agents which are sorbed into the polymer material during storage. The highest concentrations were found for limonene, diethylhexyl phthalate and the isopropyl esters of myristic and palmitic acid, which are present in the concentration range of 50 ppm to 200 ppm. Many odour compounds and preservatives are determined in concentrations of about 0.5 ppm and 10 ppm. They came to the conclusion that due to the concentration and nature of contaminants found in the investigated HDPE samples the recycled material is suitable only for non-food packaging. In a second study Huber and Franz 14 investigated a total amount 79 polymer samples (HDPE, PP, PS and PET) from controlled recollecting sources. As a 502 Novel food packaging techniques result they found limonene in nearly all polymer samples independent of the polymer type in concentrations up to 100 ppm for polyolefines (HDPE and PP) and 12 ppm and 3 ppm for PS and PET, respectively. Limonene can be considered as a marker substance for post-consumer polymers. It is interesting to note that the differences in the limonene concentration are in line with the diffusion behaviour of the polymers. In addition to limonene they found phthalates esters, alkanes, 2,6-di-tert-butyl-4-hydroxytoluene and oligomers but no hints for misuse of the bottles for storage of toxic chemicals. They concluded that most of the investigated (conventionally recycled) polymers are excluded from closed loop recycling due to the fact that in the polymers substances can be detected which are not in compliance with the European positive list system. It should be noted here that this is an inherent problem of positive lists in view of food law compliance of recycled polymers as well as virgin polymers. A threshold of regulation concept should offer a solution of assuming that a certain concentration of non-regulated compounds is of no concern for consumers’ health. 23.3.3 Recycling technology Today a considerable diversity in recycling technologies can be found, although all of them have the same objective which is to clean up post-consumer plastics. Most of them first use a water-based washing step to reduce surface contamination and to wash off dirt, labels and clues from the labels. The material is also ground to flakes during one of the first steps in the recycling process. In most cases these washing steps are combined with separating steps where different materials like polyolefines of PET are separated due to their density. It is obvious, that the cleaning efficiency of these washing processes is normally very different, depending on time, on hot or cold water-based washing or depending on the detergents added to the washing solution. However, typical washing processes are able to remove only contaminants from the surface of the polymers. 15,16 They are not able to remove organic substances which have migrated in the polymer. Therefore the purity of washed flakes is usually not suitable for closed-loop recycling. A simple remelting or re-extrusion of the washed fakes has an additional cleaning effect, 17 however the purity is usually not sufficient for reuse in the sensitive area of food packaging. So-called super-clean processes for closed-loop recycling of packaging materials therefore use further deep cleansing steps. Although there are many technologies commercially available the deep cleansing processes normally use heat and temperature, vacuum or surface treatment with chemicals for a certain time to decrease the concentration of unwanted substances in the polymers. The research on the cleaning efficiency of such super-clean recycling processes has shown that the existing recycling technologies are distinct in terms of rejection of unsuitable material, removal of contaminants and dilution with virgin material. Each of these stages in recycling uses special processes which have an effect on the quality of the finished recyclate containing packaging. Recycling packaging materials 503 23.4 Testing the safety and quality of recycled material 23.4.1 Challenge test The cleaning efficiency of super-clean processes is usually determined by challenge test. This challenge test is based on an artificial contamination of the input material going into the recycling process. Drawing up a worst-case scenario this challenge test simulates the possible misuse of the containers for the storage of household or garden chemicals in plastic containers. The first recommendations for such a challenge test are coming from the American Food and Drug Administration (FDA) 18,19 in 1992. It was a very pragmatic approach. The FDA originally suggested realistic contaminants like chloroform, diazinon, gasoline, lindane, and disodium monomethyl arsenate for use in challenge tests. However it has been shown in the past that the stability of these surrogates during recycling is in some cases not sufficient. Also the analytical methods in order to detect the surrogates are often difficult to establish and have high detection limits. It is easy to understand that the surrogates used in a challenge test should not degrade during all recycling steps. Otherwise the cleaning efficiency will be better than reality, with adverse consequences towards consumers’ safety. In the last ten years the selection of the surrogates has moved to chemicals with more model character. This development was supported by the fact that the range of chemicals available to the customers is extremely limited in practice, especially in the case of known genotoxic carcinogens. The surrogates used today in challenge tests cover the whole range of physical properties like polarity and volatility as well as the chemical nature of the compounds. Additionally, in some surrogates very aggressive chemicals towards the polymer are introduced. However, if too aggressive chemicals are used the physical properties of the polymer and the diffusion behaviour might be changed, which reduces the perception of the challenge test. Nowadays volatile chemicals like toluene, chlorobenzene, chloroform or 1,1,1-trichloroethane as well as non- volatile substances like phenyl cyclohexane, methyl stearate, tetracosane, benzophenone, methyl salicylate and methyl stearate are typically used. Of course, other substances with defined physical and chemical properties can be used for a challenge test. It should be kept in mind that such a test should challenge the recycling process in a worst-case scenario. If the resultant recyclate meets the food law requirements even under such a worst case scenario the process is able to produce recyclates suitable for reuse in packaging applications. In the last decade there have been controversial discussions between scientists, industry and authorities, in view of the worst-case character of such challenge tests. In most cases these discussions arise from the lack of information about the average contamination in the input materials for recycling. As mentioned above, the worst-case scenario depends on the concentrations of undesired substances in the post-consumer plastics as well as the frequency of misuse of plastic containers. With knowledge of contamination appropriate safety margins for each polymer type can be defined. 504 Novel food packaging techniques 23.4.2 Cleaning efficiency of conventional recycling processes Post-consumer PET which are going into packaging applications are usually recycled with super-clean recycling processes. However, these processes use conventional washing steps as well as several deep-cleansing steps in order to eliminate undesired post-consumer substances from the PET polymer matrix. Therefore the cleaning efficiency of conventional washing processes is of interest because it influences the input concentration of post-consumer substances in feedstock material going into the deep-cleansing processes. In the literature there are a few studies on the cleaning efficiency of conventional recycling processes. These processes contain washing and surface drying steps followed in some cases by remelting of the post-consumer material. Komolprasert and Lawson 15 determined the influence of NaOH concentration, mixer speed and temperature on removal of the surrogate tetracosane from spiked PET. In this study percentages of residual tetracosane in the PET flakes which were washed in small-scale experiments using 13 different conditions were determined. The results show that the tetracosane concentration in the washed flakes was 1.4 to 3.3% of the initial spiked level. As a result only mixer speed and temperature showed a significant effect on removal of the surrogate tetracosane from the PET flakes, while the effect of NaOH concentration was insignificant. The percentage of non-volatile hydrocarbon residues in washed PET flakes varies with the initial concentration. The study determined a removal of 89 to 97% of each hydrocarbon by washing. In a second study Komolprasert and Lawson 16 determined the effect of washing and drying on the removal of surrogates in spiked PET flakes as well as in spiked PET bottles. They concluded that the combination of washing and drying removes 97 to 99% of the organic surrogates from the spiked PET bottles. The copper concentration was found to be 21% of the initial concentration after washing and drying (remark: the low cleaning efficiency for the copper organic compound is most probably due to the instability of this surrogate. It reacts during recycling to CuO which cannot be removed. This behaviour shows that metal organic compounds are in general unsuitable as surrogates for challenge tests). In case of spiked PET flakes washing and drying removes more than 99% of the initial concentration of the organic surrogates. The high cleaning efficiencies of conventional washing and drying processes are most probably due high temperatures applied during the drying step and due to the fact that contaminants rarely penetrate more than a few m into the polymer surface. This is in agreement with the result that the initial concentrations of the surrogates in spiked bottles are much lower than those in flakes, because the surface area of flakes is higher than in bottles. A third study from Komolprasert et al. 17 evaluates the decontamination by remelting in a laboratory extruder. The results show that remelting can further reduce the contamination of spiked PET. However, from the data given in this paper, the amount of this reduction is very difficult to evaluate, because of the fact that the some of the applied surrogates (diazinon, malathion, metal organic copper compound) are not stable during extrusion. In addition volatile Recycling packaging materials 505 substances like toluene are almost completely removed during washing, so that an evaluation of the cleaning effect during remelting on basis of these surrogates is impossible. In conclusion, conventional washing processes are able to reduce the input concentrations of post-consumer substances in flakes. The washing process itself most probably removes only contaminants on the surface of the flakes whereas thermal drying processes are also able to decrease substance which sorbed into the flakes. Remelting processes further reduce the contamination. Due to the fact that conventional recycling processes use a wide range of parameters and equipment, a general conclusion and a quantification of the cleaning effects for washing, drying and remelting processes is not possible on basis of the above mentioned results. 23.4.3 Cleaning efficiency of super-clean processes In the last decade studies were undertaken to quantify the residual amounts of chemical substances in the material after deep-cleansing. Therefore the cleaning efficiency of super-cleaning recycling processes is well known. Additionally to the challenge test, the quality assurance of post-consumer recycle (PCR) PET is based on a feedstock control and an analytical quality assurance. Literature data about cleaning efficiencies of super-clean recycling processes are very rare. Three studies of the cleansing efficiency of super-clean recycling processes for PET are published by Franz and Welle. 20,21,22 The process investigated in the first two studies 20,21 contains the key steps: washing, re-extrusion and solid state polycondensation (SSP). The process was challenged with three different surrogate concentration levels. As a result the cleaning efficiencies for the different surrogates and contamination levels are between 94 and 99%. 20 The most challenging substance is benzophenone. The results show no significant dependency on the input concentration of the surrogates going into the process. It should be noted here, that this process was tested without a washing process. Including a conventional washing process, the cleaning efficiencies are increased to more than 99.3% even for benzophenone. 21 In the third study 22 a recycling process without solid stating was investigated. Except for benzophenone, the investigated recycling process reduces all surrogates by more than 95% for initial concentrations below 100 ppm and more than 90% for initial concentrations between 100 and 500 ppm. For that most challenging substance, benzophenone, a cleaning efficiency of approximately 77% at an initial contamination level of 294 ppm was obtained. In conclusion the determined cleaning efficiencies are lower than those of processes with solid stating. However, the specific migration of all surrogates from PET bottles made from contaminated and recycled PET was detected to be far below the migration limit of 10 ppb. 506 Novel food packaging techniques 23.4.4 Considerations on migration evaluation Migration from a given food/plastic package system is essentially influenced by kinetical (diffusion in plastic and food) as well as thermodynamic (equilibrium partitioning between plastic and food) factors. It is useful to start in migration evaluations as a worst assumption with total mass transfer scenarios based on knowledge of the starting concentration of a given migrant in the plastic. If this calculation leads to exceeding a migration limit, then it is advisable and necessary to refine the evaluation strategy and take account of partitioning and diffusion as the crucial parameters for migration. Complete scientific background and guidance on how to proceed can be found in the literature. 2 The FDA suggests that dietary exposures to contaminants from recycled food contact articles at a concentration of 0.5 ppb or less generally are of negligible risk. 18,19,23 With help of so-called consumption factors (CF) these dietary exposures can be converted into migration limits. For recycled PET for food contact use, for instance, the FDA system applies a CF = 0.05 as the currently valid consumption factor for post-consumer plastics and therefore the migration limit of PET recyclate-containing packages is 10 ppb for each individual substance. On the other hand, the migration limit can be converted into a maximum bottle wall concentration for any substance occurring in post- consumer plastics (including substances from virgin polymers). For example, for PET the maximum concentration in the PET material which correlates with 10 ppb dietary intake level is 0.22 ppm for a typical PET container at a thickness of 0.5 mm. This calculation is based on very conservative assumptions that all PET bottles are contaminated and that the contaminants are assumed to migrate completely from the bottle into the foodstuff. The contaminant limits calculated above also assume 100% recycled resin content in the finished article. It is generally known that the diffusion-controlled migration is usually much lower than the complete transfer of substances into the foodstuffs, and this especially for low diffusivity polymers like PET. Migration from virgin and post- consumer PET has been considered in numerous investigations where the low diffusion and migration rates have been reported and confirmed. 21,22,24 Therefore, diffusion models 25,26,27 provide an interesting scientific tool for a more realistic correlation between the allowed upper migration limit in the packed foodstuff and the corresponding maximum allowable concentration in the polymer. 18,19,28 A generally recognised migration model based on diffusion coefficient estimation of organic chemical substances in polymers 2 has been finished recently within the European project SMT-CT98-7513 ‘Evaluation of Migration Models in Support of Directive 90/128/EEC’. 29 Using this model the curves in Fig. 23.1 were calculated, which presents a correlation between migration into food and the corresponding maximum allowable concentrations of the surrogates in the bottle wall in dependency of the molecular weight for a PET bottle (assumption 1 l content with 600 cm 2 packaging surface). The migration or the corresponding residual concentration in the bottle wall was calculated for 95% ethanol at contact conditions of 40oC for 10 d. For most applications these scenarios are worst-case conditions overestimating the real migration situation by factors of at least 100. In Recycling packaging materials 507 view of challenge tests and particular focus on surrogates the following very conservative maximum allowable concentrations of surrogates in the bottle wall can be calculated independently of the package thickness: toluene 4.5 ppm, chlorobenzene 5.5 ppm, phenyl cyclohexane 7.5 ppm, benzophenone 8.6 ppm and methyl stearate 17 ppm. These concentrations can be considered to correlate safely with the 10 ppb migration limit for any food or simulant at test conditions of 10 days at 40oC. Hot-fill conditions are also covered by the above mentioned modelling data. Using test conditions of 1 h at 70oC followed by 10 days at 40oC, which are the usual test conditions for hot-fill testing, instead of only 10 days at 40oC the calculated migration rises only insignificantly. Going to a more severe condition, e.g. 30 min at 100oC followed by 10 d at 40oC the factor is 1,21. This shows that the migration from PET containers into food simulants (e.g. 95% ethanol as a worst case) are very low even under hot-fill conditions. 23.4.5 Sensory Test Requirements Huber and Franz investigated the sensory properties of conventionally recycled polymers (HDPE, PP, PS and PET). 14 They found in all samples the polymer specific odour found in virgin polymers. Nevertheless, all of the recycled polymers could be identified due to additional odour notes. For PET the lowest odour deviation was noticed and an increasing off-odour was perceptible from PS to PP and HDPE. However, the results are not surprising because in all investigated polymer samples flavour compounds like limonene can be found in Fig. 23.1 Correlation of migration into food and calculated maximum allowable concentrations (in ppm) of the surrogates in the bottle wall in dependency of the molecular weight for a 1 I PET bottle in 95% ethanol (10 d at 40oC). 30 508 Novel food packaging techniques significant concentrations, which are linked to sorbed compounds from the first use of the packaging materials (see Section 23.2.2). A deep cleansing of these polymers might influence the sensory properties in a positive way. However the sensory properties of recycled polymers are a crucial parameter for a closed loop recycling and should be investigated in case by case studies with the final recyclate containing packaging materials. This is due to the fact that odour threshold limits of some flavour compounds are very low and, in a few cases, below the analytical detection limits so that the results of the challenge test cannot be used for the sensory evaluation of recycled polymers. As an important consequence, to comply with the legal requirements of any legislation sufficient sensory inertness of the recycled PET product of food contact articles needs to be assured and this can only be achieved by appropriate sensory testing. Test conditions which in many cases can serve as worst case is storage of the article in direct contact with an appropriate food simulant (for instance water as a most severe test medium) for 10 days at 40oC. However, depending on the particular application modified tests may be more suitable. 23.5 Using recycled plastics in packaging Technically, recycled plastics can, in principle, be applied in direct food contact applications or protected from direct food contact by a functional barrier. From a legal point of view, there may be limitations due to different regulations in the European countries and the still missing harmonised rules for EU. In any case, the use of recycled plastic materials in packaging applications has to comply with the relevant regulations and must not be at the expense of the public health, nor should it alternate the filling’s quality. 31 In the following, practical examples of recycled plastics food packaging applications covered by a functional barrier as well as in direct food contact are described. 23.5.1 Indirect contact applications applying functional barriers In the most general understanding the concept of a functional barrier can be defined as follows: A functional barrier is a layer in the package which protects the food from external influences under the applied fill and storage conditions. In most cases the functional barrier is the food contact layer or, in complex multi-layer structures, one very close to it. This layer acts as a barrier against contamination from the packaging’s environment in general and, more specifically, from the recycled core layer or outer compartments of the package. The functional barrier efficiency must not be confused with an absolute physical barrier such as glass or metal layers. It is related to a ‘functional’ quantity in terms of mass transfer which is dependent on the technological and application-related parameters of the respective food-package system. These parameters are: Recycling packaging materials 509 ? manufacture conditions of the package ? thickness of the functional barrier layer ? type of functional barrier plastic ? molecular weight and chemical structure of penetrants (contaminants) ? concentration and mobility of contaminants in the matrix behind the functional barrier ? time period between manufacture of package and filling ? type of foodstuff, i.e. fat content, polarity etc. ? filling conditions and storage (time, temperature) of the packed foodstuffs More scientific background and guidance can be found in the published literature 31,32,33 as well as in the case studies described below. Three-layer PP cups for dairy products In 1994 a study was presented 34 where the safety in food contact use of symmetrically coextruded three-layered polypropylene (PP) cups with recycled post-consumer PP in the core layer (mass fraction 50%) and virgin food grade PP in the adjacent layers was investigated. The recycled PP, which contained about 95% PP and 5% PS, was completely under source control in the recollection system and had been used in its prior application for packaging yoghurt. The intended application for the recycled material was again packaging milk products such as yoghurt with storage for short times under refrigerated conditions. The essential working strategy in this study was to compare the recycled plastic with new, food grade plastic material of the same type. This comparison included experimentally three investigation levels: (1) compositional analysis of the raw materials (virgin versus recycled PP pellets), (2) compositional analysis of the finished food contact articles (virgin versus recycled cups) (3) migration testing on both types of cup (virgin and recycled) under regular as well as more severe test conditions. After identification and quantification of post-consumer or recycling-related potential migrants on levels (1) and (2) these compounds were used as indicator substances to be monitored in migration measurements on level (3). The major post-consumer related compound was identified as limonene, a flavour compound which can be found in many foodstuffs and also in the non- food area. In summary it turned out that none of post-consumer or recycling- related substances could be analytically detected in the food simulants (at a detection limit of 13 ppb) under prescribed migration test conditions. However, from the results obtained under more severe test conditions, it could be concluded finally that for the compound with the highest migration, limonene, the migration into a milk product will be below 1 ppb and for other post-consumer substances far below of 1 ppb. In conclusion, based on the US 510 Novel food packaging techniques FDA threshold of regulation concept 18 the intended application was con- sidered to be safe. Multi-layer PET bottles for soft drink applications In 1996 a study was published 35 in which the effectiveness of a virgin PET layer in limiting chemical migration from recycled PET was investigated. For this purpose three-layer bottles were prepared with an inner core (buried layer) of PET which was deliberately contaminated. The model contaminants used were toluene, trichloroethane, chlorobenzene, phenyl decane, benzophenone, phenyl cyclohexane and copper(II) acetylacetonate. As a result no migration was detected through a barrier of virgin PET of 186 39 m thickness into 3% acetic acid using general migration test conditions of 10 days at 40oC and also after 6 months storage at room temperature. Also migration testing with 50% and 95% ethanol as severe contact media which are relatively aggressive to PET did not lead to measurable migration rates. Consideration of diffusion models using limonene as substance for which diffusion coefficients were available, gave estimates that for a 100 m thick PET layer a breakthrough of a substance with comparable molecular weight would take place after 7.5 years or 0.8 years at room temperature or 40oC, respectively. It was concluded that an intact PET bottle layer in contact with the food represents an efficient functional barrier against migration from any possible contaminant encapsulated in a recycled PET material under normal conditions of use for soft drinks. Today, multi-layer PET soft drink bottles have received clearance for use in Austria, Belgium, Finland, France, Norway, Sweden and the United Kingdom. Studies on multi-layer PET and PET films for food packaging In another project, 36 several coextruded three-layered PET films spiked in the core layer with surrogates (toluene and chlorobenzene) and having a PET barrier layer thickness between 20 to 60 m, were systematically investigated with respect to their migration behaviour under different test and contact medium conditions. It was observed that the migration measured through the different barrier layers was predictable, and a diffusion model for predicting the functional barrier properties of layered films based on Fickian diffusion was presented. Also the effects of diffusion from the core layer to a virgin barrier layer during the coextrusion process was found necessary to be considered for reliable prediction of migration. On the basis of the presented mathematical model, maximum allowable concentrations can be established for a core layer for a given barrier thickness while still fulfilling threshold or specific migration limit requirements. In similar studies with symmetrical three-layer films spiked again in the core layer with toluene and chlorobenzene the functional barrier behaviour of high impact polystyrene (HIPS) was investigated. 27 The applied thicknesses of the HIPS barrier layer ranged higher than the above PET example and were 50 m, 100 m and 200 m. The contact medium was 50% ethanol which is a recognised medium for fatty food products for this plastic, and testing was carried out at Recycling packaging materials 511 40oC up to 76 days. From the results it was concluded that HIPS was an appropriate functional barrier under given application parameters which need to be optimised for the particular purpose. Generally, layer thicknesses from 100 m to 200 m were found to be very efficient, and this even in the case of exaggerated test conditions as applied in this study for fatty contact. When considering aqueous food products and room or cooling temperature applications, this conclusion is still much more valid and of general character. Again, as with the PET study, the contamination effect from the core layer to the virgin barrier layers during the high temperatures of the coextrusion process was investigated. For instance, for a 50 m thick HIPS layer it turned out that the same contamination effect of the food contact surface with the surrogate toluene, which is obtained after one year’s storage at room temperature, is achieved within 1 second only at the coextrusion temperature of 200oC. 23.5.2 Direct contact applications Mono-layer PET bottle for soft drink applications As mentioned before, PET is one of the most favoured candidates for closed- loop recycling. Due to higher costs of manufacturing multi-layer bottles, the bottle manufacturing and recycling companies started the development of recycling processes without a functional barrier of virgin PET. One decade later several super-clean recycling processes were established on an industrial scale. 1 In 2002, companies in Europe have built an overall recycling capacity of about 65.000 tons per year of super-clean post-consumer PET which can be used in direct food contact applications. The cleaning efficiencies of all the applied deep-cleansing recycling processes were investigated by challenge tests and the cleaning efficiencies are well known (see for example Lit. 20,21,22 ). In Europe today, the mono-layer direct food contact approach has received clearance for use in Austria, Belgium, France, Germany, The Netherlands, Norway, Sweden and Switzerland. Mono-layer HDPE bottles for fresh milk In 2002 the following project was started in Northern Ireland. 37 Milk bottles were recovered by a deposit system and were subjected to a bottle-to-bottle recycling process. Due to the recovery system the recycled HDPE was completely under source control and had been used in its prior application only for packaging fresh milk. The recovered material was recycled first by a conventional washing based recycling process and then further deep-cleansed using a super-clean process. Subsequently the recycled material was used with a content of 20 to 30% without a functional barrier. The intended application for the recycled material was again bottles for fresh milk with short time storage under refrigerated conditions. The project had several R&D phases before: after a screening of post- consumer HDPE milk bottles for compounds which are potential migrants the deep-cleansing process was evaluated and optimised. Subsequently, the 512 Novel food packaging techniques cleaning efficiency of the recycling process was determined with a challenge test. As a result only HDPE related compounds such as oligomers could be detected in the recycled polymer after deep-cleansing. In addition an online sniffing device based on so-called electronic noses was integrated into the recycling process. This sniffing device is able to detect potential migrants, such as solvents or other volatile substances, which might be introduced into the recycling process. Based on the challenge test results, upper limits for the concentration of volatile substances could be defined so that any HDPE lots with higher levels can be detected, and separated for being reused in non-food packaging areas. These higher recycling efforts over-compensated the principal lower material suitability of HDPE for closed loop recycling in comparison to PET. Another point of interest is, that the project was started in Northern Ireland at a small market scale which is under good control. The HDPE milk bottles were provided by only two bottle manufacturers, which are integrated into the project. By reading the bar code the vendors are able to separate bottles from these two manufacturing companies from other milk bottles which are rejected. Therefore, only milk bottles from bottle suppliers and filling companies which support the project are directed to the bottle-to-bottle recycling process. The recycling company, in principle, is therefore in a position to react on negative impacts of applied clues, label, colours etc. and can control its recyclate production. 23.6 Future trends For PET, a low diffusivity polymer, closed-loop recycling is now established in several countries all over the world. The HDPE study described in Section 23.5.2 shows that the combination of source control, efficient process technology and quality control using modern sniffing devices enables manufacturing companies also to re-use packaging plastics in direct food contact which have a higher diffusivity than PET. However, it must be realised that compared to PET recycling of polyolefines will always be of much more specific character i.e. limited to a certain first application and a relatively narrow and overseeable recovery system if it is intended to reuse the plastic for sensitive applications such as direct food contact. On the other hand recycling of polyolefine plastic crates into new ones for relatively insensitive applications, such as transport containers for fresh fruits or vegetables, is a less challenging issue and can therefore be dealt with in a more general way. Current and future technological improvements and further developments in recovery, sorting and recycling technologies will be an important basis for the expected increasing market shares of recycled polymers in the packaging area. Accompanied by increasing knowledge of possible post-consumer contaminant levels and further improving developments in analytical control systems, e.g. complete inline control of recyclate production, using appropriate sniffing devices, will enable the potential risk of exposure to the consumer of unwanted Recycling packaging materials 513 recycling-related compounds at the necessary low levels and at the expectable increasing use in the market place. However, the food packing market is not static. Further developments leading to more complex packaging systems, e.g. introduction of new barrier coating systems, multilayers or new plastics additives or active substances, may have an impact on closed-loop recycling which needs to considered at an early stage of the packaging developments. In the PET packaging area the introduction of so- called acetaldehyde scavengers can lead for instance to a yellowing of the recycled material, a negative optical appearance of the polymer which, however, does not pose a risk for the consumer but decreases the market value of recyclate-containing packaging materials. Therefore, in the future, closed-loop recycling will be a challenge which can only be efficiently and successfully managed by collaboration between recyclers and the packaging industry chain. 23.7 Sources of further information and advice 23.7.1 European Projects ‘Recycle Re-use’ and ‘Recyclability’ In the last decade the European Commission has supported two projects dealing with the question of recyclability and reusability of post-consumer plastics new food packaging applications. The first project AIR2-CT93-1014 3 is dealing with plastics packaging materials recovered from packaging waste. The second project FAIR CT98-4318 38 focuses on PET as the most favourable candidate plastics for direct food contact. Two other sections of the project are dealing with paper and board and recycled plastics covered with functional barriers. Both project reports provide deeper information on analytical approaches and their validation to assess the opportunity of recycling of post-consumer plastics into food packaging applications. Based on the results of the European Project FAIR CT98-4318 32 proposals for the forthcoming legislation were written and filed with the European Commission. One document is based on the results of the Europe-wide screening of post-consumer PET flakes and on migration considerations. 39 The other document gives guidance on the use of functional barriers. 33 23.7.2 US FDA Points to Consider In 1992 and 1995 the FDA published two guidelines for industry dealing with post-consumer plastics for direct food contact applications. 18,19 These guidelines provide recommendations about testing the cleaning efficiency of the investigated recycling process and the maximum content of post-consumer substances in recyclate-containing packaging materials as well as threshold limits for migration. Based on the agency’s reviews on petitions and on own research projects the FDA now provides an update of their guidelines. 5 This update integrates new knowledge, mainly for PET, of the contamination of post- consumer material and challenge tests. Especially for PET recommendations are 514 Novel food packaging techniques given for feedstock material from non-food applications, which are intended to be recycled into food packaging. The FDA also provides information about all ‘non objection letters’ on their internet homepage. 40 23.7.3 European ILSI document In 1997 an expert group under the responsibility of ILSI Europe has proposed specific guidelines on the re-use of recycled plastics in food packaging. 41 These guidelines, published in 1998, are based on the results obtained from the above- mentioned European ‘Recycle Re-use’ project. The intention of the document was to provide information for industry about the European view of closed-loop recycling of post-consumer plastics. The document gives recommendations for recycling or packaging companies, which want to introduce post-consumer plastics into food contact applications. 23.7.4 German BfR recommendations The German BfR (former BgVV) published in 2000 recommendations on the mechanical recycling of post-consumer PET for direct food contact applications. 28 This document is the result of a discussion by the German ‘Plastics Commission’ on PET bottle-to-bottle recycling. The BfR document gives recommendations for source control, challenge test and for the quality assurance of post-consumer PET intended to come into direct food contact. 23.8 References 1. K. FRITSCH, F. WELLE, Polyethylene terephthalate (PET) for packaging, Plast Europe, 2002, 92(10), 40–1. 2. O.-G. PIRINGER, A. L. BANER (Editors), Plastic Packaging Materials for Food – Barrier Function, Mass Transport, Quality Assurance and Legislation, 2000, WILEY-VCH, Weinheim, New York. 3. Final report of EU funded AIR project AIR2-CT93-1014, Programme to establish criteria to ensure the quality and safety of recycled and re-used plastics for food packaging, Brussels, December 1997. 4. F. L. BAYER, Polyethylene terephthalate (PET) recycling for food contact applications: Testing, safety and technologies – A global perspective, Food Additives and Contaminants, 2002, 19, Supplement, 111–34. 5. T. H. BEGLEY, T. P. MCNEAL, J. E. BILES, K. E. PAQUETTE, Evaluating the potential for recycling all PET bottles into new food packaging, Food Additives and Contaminants, 2002, 19, Supplement, 135–43 6. D. PIERCE, D. KING, G. SADLER, Analysis of contaminants in recycled poly(ethylene terephthalate) by thermal extraction gas chromatography – mass spectrometry, 208th American Chemical Society National Meeting. Washington DC, August 25, 1994, 458–71. Recycling packaging materials 515 7. G. D. SADLER, Recycled PET for food contact: Current status of research required for regulatory review, Proceedings: Society of Plastic Engineering Regional Technical Conference, Schaumburg, IL, USA, November 1995, 181–91. 8. R. FRANZ, Programme on the recyclability of food-packaging materials with respect to food safety considerations – Polyethylene terephthalate (PET), paper & board and plastics covered by functional barriers, Food Additives and Contaminants, 2002, 19, Supplement, 93–100. 9. F. WELLE, R. FRANZ, Typical contamination levels and analytical recognition of post-consumer PET recyclates, Congress Proceedings: EU-Project Workshop ‘Recyclability’, Varese, February 11, 2002. 10. R. FRANZ, M. MAUER, F. WELLE, European survey on post-consumer poly(ethylene terephthalate) materials to determine contamination levels and maximum consumer exposure from food packages made from recycled PET, Food Additives and Contaminants, submitted for publication. 11. B. H. ALLEN, B. A. BLAKISTONE, Assessing reclamation processes for plastics recycling, 208th American Chemical Society National Meeting. Washington DC, August 25, 1994, 418–34. 12. F. L. BAYER, D. V. MYERS, M. J. GAGE, Consideration of poly(ethylene terephthalate) recycling for food use, 208th American Chemical Society National Meeting. Washington DC, August 25, 1994, 152–60. 13. M. HUBER, R. FRANZ, Identification of migratable substances in recycled high density polyethylene collected from household waste, Journal of High Resolution Chromatography, 1997 29, 427–30. 14. M. HUBER, R. FRANZ, Studies on contamination of post-consumer plastics from controlled resources for recycling into food packaging applications, Deutsche Lebensmittel-Rundschau, 1997, 93(10), 328–31. 15. V. KOMOLPRASERT, A. LAWSON, Effects of aqueous-based washing on removal of hydrocarbons from recycled polyethylene terephthalate (PETE), Congress Proceedings ANTEC’94, San Francisco, 1994, 2906-9. 16. V. KOMOLPRASERT, A. LAWSON, Residual contaminants in recycled poly(ethylene terephthalate) – Effects of washing and drying, 208th American Chemical Society National Meeting. Washington DC, 1994, 435–44. 17. V. KOMOLPRASERT, A. R. LAWSON, A. GREGOR, Removal of contaminants from RPET by extrusion remelting, Packaging, Technology and Engineering, 1996, September, 25–31. 18. Points to consider for the use of recycled plastics in food packaging: Chemistry considerations, US Food and Drug Administration, Center for Food Safety and Applied Nutrition (HFF-410), Washington, May 1992. 19. Guidelines for the safe use of recycled plastics for food packaging applications, Plastics Recycling Task Force document, National Food Processors Association, The Society of the Plastic Industry, Inc. March 1995. 516 Novel food packaging techniques 20. R. FRANZ, M. HUBER, F. WELLE, Recycling of post-consumer poly(ethylene terephthalate) for direct food contact application – a feasibility study using a simplified challenge test, Deutsche Lebensmittel-Rundschau, 1998, 94(9), 303–8. 21. R. FRANZ, F. WELLE, Post-consumer poly(ethylene terephthalate) for direct food contact application – final proof of food law compliance, Deutsche Lebensmittel-Rundschau, 1999, 95, 424–7. 22. R. FRANZ, F. WELLE, Post-consumer poly(ethylene terephthalate) for direct food contact application – Challenge-test of an inline recycling process, Food Additives and Contaminants, 2002, 19(5), 502–11. 23. F. L. BAYER, The threshold of regulation and its application to indirect food additive contaminants in recycled plastics, Food Additives and Contaminants, 1997, 14, 661–70. 24. V. KOMOLPRASERT, A. R. LAWSON, Considerations for the reuse of poly(ethylene terephthalate) bottles in food packaging: migration study, Journal of Agricultural and Food Chemistry, 1997, 45, 444–8. 25. A. L. BANER, J. BRANDSCH, R. FRANZ, O. G. PIRINGER, The application of a predictive migration model for evaluation the compliance of plastic materials with European food regulations, Food Additives and Contaminants, 1996, 13, 587–601. 26. T. H. BEGLEY, H. C. HOLLIFIELD, Recycled polymers in food packaging: migration considerations, Food Technology, 1993, 109–12. 27. R. FRANZ, M. HUBER, O. G. PIRINGER, Presentation and experimental verification of a physico-mathematical model describing the migration across functional barrier layers into foodstuffs, Food Additives and Contaminants, 1997, 14(6–7), 627–40. 28. Use of mechanical recycled plastic made from polyethylene terephthalate (PET) for the manufacture of articles coming in contact with food, Bundesinstitut fu¨r Risikobewertung BfR, Berlin, October 2000. Also implemented into BfR Recommendation XVII. 29. O. PIRINGER, K. HINRICHS, Evaluation of Migration Models, Final Report of the EU-project contract SMT-CT98-7513, Brussels 2001. 30. R. FRANZ, unpublished results. 31. R. FRANZ, Safety assessment in modern food packaging applications, in: O.-G. Piringer, A. L. Baner, (editors), Plastic Packaging Materials for Food – Barrier Function, Mass Transport, Quality Assurance and Legislation. Wiley-VCH, Weinheim, 2000, Chapter 10.3, 336–57. 32. Final Project workshop of EU project FAIR CT98-4318, organised by the European Commission Joint Research Centre, Food Products Unit, and held on 10–11. February 2002 in Varese, Italy. A comprehensive download package of the presentations can be found at http://cpf.jrc.it/ webpack/projects.htm. 33. D. DAINELLI, A. FEIGENBAUM, Guidelines for functional barrier applications, oral presentation at the workshop given under Lit. 32 and downloadable from http://cpf.jrc.it/webpack/projects.htm. Recycling packaging materials 517 34. R. FRANZ, M. HUBER, O.-G. PIRINGER, Testing and evaluation of recycled plastics for food packaging use – possible migration through a functional barrier, Food Additives and Contaminants, 1994, 11(4), 479–96. 35. R. FRANZ, M. HUBER, O.-G. PIRINGER, A. P. DAMANT, S. M. JICKELLS, L. CASTLE, Study of functional barrier properties of multilayer recycled poly(ethylene terephthalate) bottles for soft drinks, Journal of Agricultural and Food Chemistry, 1996, 44(3), 892–7. 36. O. PIRINGER, M. HUBER, R. FRANZ, T. H. BEGLEY, T. P. MCNEAL, Migration from food packaging containing a functional barrier: mathematical and experimental evaluation, Journal of Agricultural and Food Chemistry, 1998, 46(4), 1532–8. 37. Personal Communication to the authors from Green Cycle, Armagh, Northern Ireland, internet http://www.greencycle.info. 38. Final report of EU project FAIR CT98-4318 ‘Programme on the Recyclability of Food Packaging Materials with Respect to Food Safety Considerations – Polyethylene Terephthalate (PET), Paper and Board and Plastics Covered by Functional Barriers’, Brussels, 2003. 39. R. FRANZ, F. BAYER, F. WELLE, Guidance and criteria for safe recycling of post consumer polyethylene terephthalate (PET) into new food packaging applications, Guidance document prepared within EU project FAIR CT98- 4318, submitted for publication. 40. Recycled Plastics in Food Packaging, US Food and Drug Administration, Center for Food Safety & Applied Nutrition, Office of Premarket Approval; internet: http://vm.cfsan.fda.gov/~dms/opa-recy.html. 41. Recycling of Plastics for Food Contact Use, Guidelines prepared under the responsibility of the International Life Sciences Institute (ILSI), European Packaging Material Task Force, 83 Avenue E. Mounier, B-1200 Brussels, Belgium, May 1998. 518 Novel food packaging techniques