Critical review on challenge tests to demonstrate decontamination of polyolefins intended for food contact applications

Role of quality assessment of the recycled packaging material in determining its safety profile as food contact material

Food packaging waste significantly impacts global environmental changes, prompting the adoption of a green circular economy approach. Recycling packaging waste is a critical element of this strategy. However, it faces challenges related to the quality of recycled materials and concerns about their safety. Thus, this review aimed to highlight different analytical methods alone or in combination to evaluate the quality of the recycled material. Furthermore, the safety and health aspects related to the migration of contaminants and their relevant regulations have also been discussed. An important parameter while selecting an appropriate recycling method is the composition and nature of the recyclate, for instance, HDPE (High-Density Polyethylene), PET (Polyethylene Terephthalate), and PP (Polypropylene) materials can be recycled using mechanical and chemical recycling, however, PVC (Polyvinyl Chloride) and PS (Polystyrene) present challenges during mechanical recycling due to lower molecular weight and complex compositions, thus are often downcycled into lower-grade products. Still, recycled papers can be more problematic than recycled plastics due to the nature of the materials and the impact of recycling. The literature review suggested that three quality properties i.e., presence of low molecular weight compounds, degree of degradation, and composition should be analyzed by using different spectroscopic, thermo-mechanical, and chromatographic techniques to obtain a detailed understanding of recycled material quality. Furthermore, recycling should be done in such a way that the migration of contaminants should be lower than the migratory limits set by the relevant authorities to avoid any toxicological effects.

Evaluation of new safety decontamination approaches at lab scale for recycled highdensity polyethylene (rHDPE) intended for food contact

BACKGROUND

The increasing use of plastic packaging materials generates concerns related to the environmental problem generated by their waste. As a result, the search for new recycling methodologies to extend the lifecycle of plastic packaging is becoming more important, without forgetting to ensure the safety of these materials. Currently, the use of recycled polyolefins as food contact materials is not widespread yet. This is because the decontamination processes currently available are insufficient to produce clean, safe materials suitable for such applications. This work is focused on the evaluation of the safety of recycled high-density polyethylene (rHDPE), and the search for strategies to achieve its decontamination.

RESULTS

To this end, three batches of flakes and three batches of pellets of rHDPE coming from the mechanical recycling of post-consumer milk bottles were analyzed. The analysis of the volatile and semi-volatile compounds present in the samples was carried out using gas chromatography-mass spectrometry (GC-MS), finding a total of 67 compounds. The strategy to achieve the decontamination of flakes and pellets of this material has been based on the application of high temperature and vacuum at lab scale, obtaining a clear decrease in volatile compounds, below 50% of the initial value in most cases when applying 120 °C during 5 h. The migration test performed in the samples (treated and untreated) to different food simulants (10 % ethanol and 3 % acetic acid, 95 % ethanol) revealed also a clear decrease of concentrations of volatiles.

SIGNIFICANCE

The findings are highly encouraging, demonstrating substantial progress toward the safe and effective use of rHDPE in specific food packaging applications. This indicates a significant step forward in the potential uses of rHDPE. Nevertheless, the lack of toxicity data for many migrants necessitates additional toxicological testing to obtain a more precise risk assessment.

Food grade plastics and Bisphenol A: Associated risks, toxicity, and bioremediation approaches

Bisphenols' widespread use in day to day life has enabled its existence in various compartments of the environment. Bisphenol A (BPA) is utilized as a monomer in manufacturing polycarbonate plastics, epoxy resins, as well as flame retardants and is also considered as an endocrine disruptor. This study focuses on determining BPA concentration in daily-use food-grade plastic containers, in addition to its toxicity evaluation in environmental samples contaminated by BPA leachates. The highest concentration of BPA was observed in black poly bags (42.78 ppm), followed by slice juice bottles and infant milk bottles. Toxicity tests revealed significant impacts on Rhizobium and Chlorella sp. as a representative species of soil and aquatic environment respectively. To biodegrade the BPA, two potential strains, Brucella sp. and Brevibacillus parabrevis, were isolated from a landfill site. Qualitative and quantitative evaluation of biodegraded BPA through U-HPLC and GC-MSMS showed various metabolites of BPA. Results indicate the native bacterial isolates as potential candidates for BPA degradation while transforming this contaminant to a less toxic and hazardous form. The study also proposes the risk associated with food-grade plastic containers and recommends to establish a sustainable way for plastic waste management.

Application of chemometric tools in the QSAR development of VOC removal in plastic waste recycling

Deodorization and, in a broader sense, the removal of volatile organic compounds (VOCs) from plastic waste have become increasingly important in the field of plastic recycling, and various new decontamination techniques have been developed. Both in research and industrial practice, the selection of VOCs has been random or unsubstantiated, making it difficult to compare studies and assess decontamination processes objectively. Thus, this study proposes the use of Statistical Molecular Design (SMD) and Quantitative Structure - Activity Relationship (QSAR) as chemometric tools for the selection of representative VOCs, based on physicochemical properties. Various algorithms are used for SMD; hence, several frequently used D-Optimal Onion Design (DOOD) and Space-Filling (SF) algorithms were assessed. Hereby, it was validated that DOOD, by dividing the layers based on the equal-distance approach without so-called 'Adjacent Layer Bias', results in the most representative selection of VOCs. QSAR models that describe VOC removal by water-based washing of plastic waste as a function of molecular weight, polarizability, dipole moment and Hansen Solubility Parameters Distance were successfully established. An adjusted-R2 value of 0.77 ± 0.09 and a mean absolute error of 24.5 ± 4 % was obtained. Consequently, by measuring a representative selection of VOCs compiled using SMD, the removal of other unanalyzed VOCs was predicted on the basis of the QSAR. Another advantage of the proposed chemometric selection procedure is its flexibility. SMD allows to extend or modify the considered dataset according to the available analytical techniques, and to adjust the considered physicochemical properties according to the intended process.

Unpacking the complexity of the polyethylene food contact articles value chain: A chemicals perspective

Polyethylene (PE) is the most widely used type of plastic food packaging, in which chemicals can potentially migrate into packaged foods. The implications of using and recycling PE from a chemical perspective remain underexplored. This study is a systematic evidence map of 116 studies looking at the migration of food contact chemicals (FCCs) across the lifecycle of PE food packaging. It identified a total of 377 FCCs, of which 211 were detected to migrate from PE articles into food or food simulants at least once. These 211 FCCs were checked against the inventory FCCs databases and EU regulatory lists. Only 25% of the detected FCCs are authorized by EU regulation for the manufacture of food contact materials. Furthermore, a quarter of authorized FCCs exceeded the specific migration limit (SML) at least once, while one-third (53) of non-authorised FCCs exceeded the threshold value of 10 μg/kg. Overall, evidence on FCCs migration across the PE food packaging lifecycle is incomplete, especially at the reprocessing stage. Considering the EU's commitment to increase packaging recycling, a better understanding and monitoring of PE food packaging quality from a chemical perspective across the entire lifecycle will enable the transition towards a sustainable plastics value chain.

Scientometric analysis of the development of plastic packaging considering the circular economy and clean technologies: A review

Plastics are alternatives to enable the distribution of industrialized products, especially food. Packaging is versatile and of great importance for the conservation of products. However, plastic packaging impacts the environment and calls for a clean technology and circular economy approach to mitigate the damage. A scientometric analysis of the relationship between plastic packaging production and the circular economy was reviewed based on the premise that research is intrinsically linked to clean technologies. VosViewer software was used to conduct the analysis, and the revision was conducted for discussion and relationship building. We concluded that there is a gap regarding the connection between the circular economy and clean technologies with plastic packaging. The development of technologies that adapt plastic packaging to the circular economy is rarely discussed. To make plastic packaging more environmentally attractive, technologies based on eco-design are necessary to achieve an alternative scenario associated with a more sustainable circular economy.

One-dimensional and comprehensive two-dimensional gas chromatographic approaches for the characterization of post-consumer recycled plastic materials

In September 2022, the European Commission published its new regulation on recycled plastic materials for food contact. It allows newly developed, non-authorized technologies and approaches, or so-called novel technologies, to be deployed in the field to generate the data needed for establishing regulatory and/or fit for purpose processes. The data shall be generated by using suitable methods, but the regulation does not give a more detailed description on those. In this study, commercially purchased buckets made of post-consumer recycled polypropylene were screened, using a number of different analytical approaches. Sample preparation methods, analysis techniques, and the data and information generated were compared. The results clearly demonstrate the need for a detailed characterization of such materials and the advantages and disadvantages of the analysis using conventional gas chromatography with flame ionization detection and mass spectrometery as well as two-dimensional comprehensive gas chromatography with time of flight mass spectrometry.

Recycling of polypropylene by supercritical carbon dioxide for extraction of contaminants from beverage cups. A comparison with polyethylene terephthalate and polylactic acid

BACKGROUND

EU policies towards a circular economy address plastic packaging as one of the significant concerns and sets ambitious recycling targets. Polyolefins (POs) cannot be recycled for food contact using conventional polyethylene terephthalate (PET) recycling approaches. Thermal degradation prevents the use of high temperatures and, consequently, decontamination of POs may be insufficient when using lower temperatures. Polypropylene (PP) beverage cups were decontaminated using supercritical fluid extraction with carbon dioxide (scCO₂ ). Decontamination efficiencies (DEs) of selected markers were determined in challenge tests following European Food Safety Authority guidelines. The effects of time (10-60 min) for PET, polylactic acid (PLA), and PP and temperature (60-80 °C) for PP were studied at constant pressure. The physical properties, sensorial properties, and overall migration of treated scCO₂ PP were analysed and compared with virgin PP.

RESULTS

PP showed the highest average DE, and PET the lowest, for all the surrogates and in all time conditions. A relative increase in the DE with the increase in process time, particularly for PET and to some extent for PLA, was seen. For PP, no significant impact of time and temperature was observed under the conditions tested. The DE of volatile surrogates was higher than that of semi-volatiles. Results indicate that the scCO₂ treatment did not affect the physical and sensorial properties, nor the overall migration of PP, although it contributes to a considerable reduction in extractable n < C24 alkanes.

CONCLUSIONS

Results indicate that scCO₂ can be used to decontaminate post-consumption PP beverage cups with higher DEs than those for PET and PLA, applying mild processing conditions. © 2022 Society of Chemical Industry.

Mechanical recyclability of biodegradable polymers used for food packaging: case study of polyhydroxybutyrate-co-valerate (PHBV) plastic

For the purpose of mechanical recycling for food contact applications, decontamination of polyhydroxybutyrate-co-valerate (PHBV) plastic was performed under different temperatures and time conditions. As expected, increasing the decontamination temperature and duration increased the decontamination efficiency, but also the degradation of the polymer. The combination 160 °C/6 h was selected as the optimal conditions that maximize contaminants removal while minimizing polymer degradation. Then the safety of the recycled PHBV under these conditions was assessed, in accordance with EFSA regulation based on bottle-to-bottle PET recycling. Decontamination of low molecular weight molecules such as toluene, chlorobenzene, and methyl salicylate was nearly complete with residual concentrations below the modeled concentrations allowed in the polymer when the adult scenario is considered. However, the higher molecular weight and lower volatility molecules exhibited acceptable decontamination efficiencies, but their residual concentrations in the polymer exceeded the maximum concentrations of no concern. The presence of these molecules allows the use of nearly 21% recycled PHBV in the new materials to meet safety criteria. It is important to keep in mind that this work, never done before, is a preliminary work on mechanical recycling of PHBV, mainly based on extrapolation of PET conditions and regulations. Much more research needs to be done to improve the decontamination process, the barrier properties of PHBV or to think about a short recycling line for PHBV.

Challenges and opportunities in sustainable management of microplastics and nanoplastics in the environment

The accumulation of microplastics (MPs) and nanoplastics (NPs) in terrestrial and aquatic ecosystems has raised concerns because of their adverse effects on ecosystem functions and human health. Plastic waste management has become a universal problem in recent years. Hence, sustainable plastic waste management techniques are vital for achieving the United Nations Sustainable Development Goals. Although many reviews have focused on the occurrence and impact of micro- and nanoplastics (MNPs), there has been limited focus on the management of MNPs. This review first summarizes the ecotoxicological impacts of plastic waste sources and issues related to the sustainable management of MNPs in the environment. This paper then critically evaluates possible approaches for incorporating plastics into the circular economy in order to cope with the problem of plastics. Pollution associated with MNPs can be tackled through source reduction, incorporation of plastics into the circular economy, and suitable waste management. Appropriate infrastructure development, waste valorization, and economically sound plastic waste management techniques and viable alternatives are essential for reducing MNPs in the environment. Policymakers must pay more attention to this critical issue and implement appropriate environmental regulations to achieve environmental sustainability.

Thermal Stability and Crystallization Behavior of Contaminated Recycled Polypropylene for Food Contact

Polypropylene is one of the most widely used polymers, especially in the food packaging industry, which causes negative environmental effects. Recycling is a good option to partially solve this environmental problem. Thus, the polymer was contaminated with a cocktail to simulate the conditions of disposal and recycling following FDA guidelines. The influence of contaminants on recycled PP was analyzed by quiescent and nonquiescent crystallization. It was found that the contaminants alter the crystallization flow since longer induction times were observed for all contaminated samples. Also, the thermal behavior was performed considering that the thermogravimetric (TGA) results indicated an increase in the stability with the presence of contaminants. Therefore, a deep investigation using the induced oxidation time and induced oxidation temperature was performed. The contaminants play an important role in the crystallization process, as well as, in the degradation of the samples. Furthermore, the use of TGA and DSC as complementary techniques is fundamental to analyze this influence.

Thermal and Mechanical Properties of the Recycled and Virgin PET-Part I

In various countries, polyethylene terephthalate (PET) represents one of the plastics with a very high recycling rate. Since currently there is no analytical method enabling direct distinction between recycled PET (rPET) and virgin PET (vPET), there are various attempts to differentiate these materials indirectly. One of these approaches claims that the recycling of PET leads to polymer chain degradation, which is reflected in changed thermal, mechanical and crystalline properties, and testing of these properties can therefore be used to distinguish rPET and vPET. However, there are many sources leading to changes in the molecular structure and consequently to the changes of the above-mentioned properties of the PET. The purpose of this study is to analyze the glass transition and melting temperature, degree of crystallinity as well as bending and impact properties of 20 different commercially available PET recyclates from 14 suppliers and evaluate the results with respect to the literature values for vPET. The main results of this study show that the range of vPET properties is so broad that all of the corresponding properties of the tested rPET lie within this range.

Comparison of the ability of UV-Vis and UPLC-Q-TOF-MS combined with chemometrics to discriminate recycled and virgin polyethylene

A growing attention is attracted to the use of recycled plastics as food contact materials, and its chemical safety research and discrimination approach are indispensable. In current study, ultraviolet-visible spectrometry (UV-Vis) and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) were used to provide spectral and mass fingerprinting for polyethylene (PE). Coupling with chemometrics, two methods were developed to discriminate recycled and virgin PE. UV-Vis combined with chemometrics could be a more accessible, simpler and faster approach. 237-331 nm in UV spectrum was regarded as marker region selected by orthogonal partial least-squares discrimination analysis (OPLS-DA) and the accuracy of both calibration and validation set could reach 100% in linear discrimination analysis (LDA) based on this region. Besides, 2314 ions were detected by UPLC-Q-TOF-MS and processed by MS-DIAL. 48 candidate chemicals were identified, including ketone, esters, carboxylic acid, alcohols and phenols, amine, nitriles, aldehydes and others. Possible origins of these compounds could be classified as plastic, food, drug, cosmetics and pesticide related. Many of these compounds are highly toxic, especially pesticide related, indicating that recycling in closed loop or sorting by the recycled plastic articles is very necessary if the recycled PE is going to be used as food contact material.

Application of Antioxidants as an Alternative Improving of Shelf Life in Foods

Oxidation is the main problem in preserving food products during storage. A relatively novel strategy is the use of antioxidant-enriched edible films. Antioxidants hinder reactive oxygen species, which mainly affect fats and proteins in food. At present, these films have been improved by the addition of micro- and nanoliposomes coated with carbohydrate polymers, which are not hazardous for human health and can be ingested without risk. The liposomes are loaded with different antioxidants, and their effects are observed as a longer storage time of the food product. The synergy of these methodologies and advances can lead to the displacement of the protective packaging used currently, which would result in food products with functional properties added by the films, an increase in shelf life, and an improvement to the environment by reducing the amount of waste.

Circularity Study on PET Bottle-To-Bottle Recycling

With the European Green Deal, the importance of recycled products and materials has increased. Specifically, for PET bottles, a high content of recycled material (rPET) is demanded by the industry and consumers. This study was carried out in a lab environment replicating real-life industrial processes, to investigate the possible impacts on rPET quality over eleven recycling loops, aiming to use high amounts of rPET repetitively. A cycle included extrusion, solid state polycondensation (SSP), a second extrusion to simulate bottle production, hot wash and a drying step. 75% rPET and 25% virgin PET were extruded in eleven cycles to simulate a recycling and production process. Samples underwent chemical, physical and biological analysis. The quality of the rPET material was not adversely affected. Parameters such as coloring, intrinsic viscosity, concentration of critical chemicals and presence of mutagenic contaminants could be positively assessed. The quality of the produced material was likely influenced by the input material’s high standard. A closed loop PET bottle recycling process using an rPET content of up to 75% was possible when following the proposed process, indicating that this level of recycled content can be maintained indefinitely without compromising quality.

A recycler's perspective on the implications of REACH and food contact material (FCM) regulations for the mechanical recycling of FCM plastics

This manuscript provides an overview of the legislative requirements for the use of mechanical recycled plastics in articles placed on the EU market, as seen from the perspective of a plastics recycler. The first part reviews the main principles included in the overarching legislation on Registration, Evaluation, Authorisation and Restrictions of Chemicals (REACH) and to what extent these are applicable for mechanical recyclers of plastics. The interactions between REACH and the Waste Framework Directive (WFD) is discussed, as well as the difficulties for recyclers to comply with certain REACH requirements. In a second part, the focus is moved to the use of recycled plastics as Food Contact Material (FCM). The scope of the different applicable EU FCM regulations is inventorised as well as the key legislative principles involved. A final section is dedicated to the discussion on the authorisation of recycling processes under the FCM regulation and the practical challenges involved for the effective introduction of FCMs containing recycled plastics. Altogether it could be concluded that the complexity of the different legal perspectives, a lack of communication and transparency within the plastic value chain together with technical challenges related to recycling processes have been hindering the effective uptake of recycled plastic FCM (with the exception for bottle PET). The development of targeted solutions across the entire value-chain, taking into account different perspectives in terms of legislation and health protection, economic growth and technical innovations, will be crucial in achieving a circular economy for plastics, including recycled plastics for FCM.

Total Life Cycle of Polypropylene Products: Reducing Environmental Impacts in the Manufacturing Phase

This paper assesses the environmental burdens of a polypropylene product throughout the product’s life cycle, especially focusing on the injection-moulding stage. The complete life cycle model of the polypropylene product has been developed from the raw material extraction and production phase through its usage to the end-of-life stage with the help of the life cycle assessment method. To find the answers to the posed problems, different impacts were analysed by GaBi 8.0 software. The analysis lasted from the cradle to the grave, expanding the analysis of the looping method. The aim of the research was to determine the energy and material resources, emissions, and environmental impact indicators. Basically, the article tried to answer three questions: (1) How can we optimize the production phase for the looping method? (2) Which materials and streams are recyclable in the design of the production process? (3) What is the relationship between life cycle stages and total life cycle of the product? As we inspect the life cycle of the product, the load on the environment was distributed as follows: 91% in the production phase, 3% in the use phase, and 6% in the end-of-life phase. The results of the research can be used to develop technologies, especially the injection-moulding process, with a lower environmental impact.

Food-Grade PE Recycling: Effect of Nanoclays on the Decontamination Efficacy

Although PE-based nanocomposites are gaining interest within the food packaging industry for their outstanding functional properties, their end-of-life has been poorly studied. The lack of identification of such materials suggests that they could end-up in the recycling pathway optimized for the decontamination of un-filled PE. The objective of the present work is to understand and quantify the mechanisms involved in the high temperature desorption of surrogates for PE nanocomposites filled with organo-modified montmorillonite (PNC), compared to conventional PE. An original experimental setup was coupled with a modelling approach to identify the two phenomena involved in the decontamination process: diffusion of the surrogate into the bulk and its evaporation at the surface. A sweep of experimental temperatures enabled the determination of diffusion and evaporation parameters for PE and PNC and the activation energies related to the diffusivity among those two materials. The effects of the introduction of clay nanofillers onto the decontamination process have been explained and recommendations for the recycling pathway have been put forward.

Thermomechanical and Morphological Properties of Poly(ethylene terephthalate)/Anhydrous Calcium Terephthalate Nanocomposites

Calcium terephthalate anhydrous salts (CATAS), synthetized by reaction of terephthalic acid with metal (Ca) oxide were incorporated at different weight contents (0–30 wt. %) in recycled Poly(ethylene terephthalate) (rPET) by melt processing. Their structure, morphology, thermal and mechanical properties (tensile and flexural behavior) were investigated. Results of tensile strength of the different formulations showed that when the CATAS content increased from 0.1 to 0.4 wt. %, tangible changes were observed (variation of tensile strength from 65.5 to 69.4 MPa, increasing value for E from 2887 up to 3131 MPa, respectively for neat rPET and rPET_0.4CATAS). A threshold weight amount (0.4 wt. %) of CATAS was also found, by formation at low loading, of a rigid amorphous fraction at the rPET/CATAS interface, due to the aromatic interactions (π−π conjugation) between the matrix and the filler. Above the threshold, a restriction of rPET/CATAS molecular chains mobility was detected, due to the formation of hybrid mechanical percolation networks. Additionally, enhanced thermal stability of CATAS filled rPET was registered at high content (T_max shift from 426 to 441 °C, respectively, for rPET and rPET_30CATAS), essentially due to chemical compatibility between terephthalate salts and polymer molecules, rich in stable aromatic rings. The singularity of a cold crystallization event, identified at the same loading level, confirmed the presence of an equilibrium state between nucleation and blocking effect of amorphous phase, basically related to the characteristic common terephthalate structure of synthetized Ca–Metal Organic Framework and the rPET matrix.

Predictive model for the Dutch post-consumer plastic packaging recycling system and implications for the circular economy

The Dutch post-consumer plastic packaging recycling network has been described in detail (both on the level of packaging types and of materials) from the household potential to the polymeric composition of the recycled milled goods. The compositional analyses of 173 different samples of post-consumer plastic packaging from different locations in the network were combined to indicatively describe the complete network with material flow analysis, data reconciliation techniques and process technological parameters. The derived potential of post-consumer plastic packages in the Netherlands in 2014 amounted to 341 Gg net (or 20.2 kg net.cap^-1.a^-1). The complete recycling network produced 75.2 Gg milled goods, 28.1 Gg side products and 16.7 Gg process waste. Hence the net recycling chain yield for post-consumer plastic packages equalled 30%. The end-of-life fates for 35 different plastic packaging types were resolved. Additionally, the polymeric compositions of the milled goods and the recovered masses were derived with this model. These compositions were compared with experimentally determined polymeric compositions of recycled milled goods, which confirmed that the model predicts these compositions reasonably well. Also the modelled recovered masses corresponded reasonably well with those measured experimentally. The model clarified the origin of polymeric contaminants in recycled plastics, either sorting faults or packaging components, which gives directions for future improvement measures.