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