How to determine functional barrier performance towards mineral oil contaminants from recycled cardboard

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.

How to make the use of recycled paperboard fit for food contact? A contribution to the discussion

Recycled paperboard contains hundreds of non-evaluated or even unidentified substances that could endanger human health if they turn out to be highly toxic. It seems as unrealistic to evaluate each of them as it is to phase out the use of the problematic ones or sort out the papers and boards introducing them into the recyclate. Therefore, measures should be taken that generally reduce migration into food, such as functional barriers or functional sorbents. A general approach is used for the recycling of plastics, particularly poly(ethylene terephthalate), PET: as not every potential contaminant can be regulated, a pragmatic approach is applied, for PET mainly on the required decontamination efficiency. Criteria are required on the required efficacy of the measures to be taken. Recycled paperboard is used for various types of food contact: mostly contact is through the gas phase (evaporation and recondensation), often indirect through other layers (e.g. internal bags or for transport boxes), seldom in wetting contact. Numerous factors have to be considered. For typical folding boxes and at least strongly dominating gas phase contact, it was proposed that no more than 1% of each contaminant in the recycled paperboard should enter the food. The efficiency of the measures required to comply with this criterion depends on the application. The three main measures are reviewed with regard to this criterion: (i) internal bags with an incorporated functional barrier (successfully used for some time), (ii) a barrier layer on the internal wall of the box (for which the design of the closures might be most critical) and (iii) functional sorbents added to the paperboard (for which the sorbent capacity is critical). For transport boxes, commonly of corrugated board (quantitatively the most important use of recycled paperboard in food contact), an adjusted or different criterion is needed.

Characterization of natural polymers as functional barriers for cellulose-based packaging materials

Cellulose-based packaging materials are currently the most commonly used food packaging materials due to their light weight, stability and affordable price. However, the use of recycled paper and board adds to the risk that undesirable substances migrate into the packed goods, since contaminants are not completely removed during the recycling process and can accumulate in the final product. The only available fast and practical solution that can be used to reduce the migration of these substances is the application of functional barriers in the packaging. The applied barriers are currently mostly synthetic, which either serve only a moderate barrier function and/or have the disadvantage that it is often more complex and expensive to recycle the resulting packaging material. The aim of this project is to evaluate different bio-based or biodegradable polymers with regards to their barrier properties. Due to the fact that the transport phenomena are mainly driven by (gas phase) migration, methods based on gas chromatography (GC), including GC coupled with mass spectrometry (GC-MS) and flame ionization detection (GC-FID), GC-FID coupled online with high pressure liquid chromatography (HPLC-GC-FID), and comprehensive GCxGC-MS were used to qualify and quantify the migrated substances. This use of a wide range of different methods and instruments yielded excellent results, allowing us to comprehensively characterize the biopolymers and their barrier function.

Diffusion Coefficients of n-Alkanes and 1-Alcohols in Polyethylene Naphthalate (PEN)

Polyethylene naphthalate (PEN) is a polyester polymer with well-known good barrier properties. PEN had been used in the food packaging area till 2012 especially as refillable bottles for soft drinks, juices, and beer. Now, PEN is mainly used in technical applications, e.g., for data storage tapes and organic light-emitting diode (OLED) applications. The aim of the study was the determination of the diffusion coefficients of organic molecules (n-alkanes, 1-alcohols) in PEN. Diffusion and partition coefficients were determined from the lag times of the permeation process of the permeants through a commercial 12 μm biaxial-oriented PEN film. In addition, activation energies of diffusion EA were calculated according to the Arrhenius approach. The activation energy of diffusion EA follows a correlation with the molecular volume V of the investigated permeants. In addition, the preexponential factor D0 follows a correlation with the activation energy of diffusion EA. The results of this study for PEN (e.g., EA, DP) were compared to literature data on PET.

Required barrier efficiency of internal bags against the migration from recycled paperboard packaging into food: a benchmark

The use of recycled paperboard and corrugated board for food packaging is in the interest of the sustainability of resources, but in most applications the food must be protected against contamination from these materials, such as by an internal bag with a functional barrier. Producers of packaging need a specification to find the most suitable and economical barrier for a given application, and the customer needs the confidence that a solution offered to him is adequate. An accurate determination of the barrier efficiency is not possible due to the large number of migrants, most of which have not been evaluated or not even identified. Hence the specification must be based on assumptions and verifiable by a simple test. The proposed benchmark presumes that the migration of all non-evaluated or even unknown substances in recycled paperboard will remain below 0.01 mg kg(-1) food, the conventional detection limit, if their transfer does not exceed 1% of the content in the paperboard. Some substances, such as mineral oil or fatty acids, will exceed the 0.01 mg kg(-1) limit, but they are known, evaluated and of no concern at the reduced migration. Since the critical substances must be assumed to be unknown, the criterion of the 1% migration is tested with three surrogate substances of similar volatility and covering a broad range of polarity. The cornerstones of the method are specified.