Predicting diffusion coefficients of chemicals in and through packaging materials

Predicting Diffusion Coefficients in Nafion Membranes during the Soaking Process Using a Machine Learning Approach

Nafion, a versatile polymer used in electrochemistry and membrane technologies, exhibits complex behaviors in saline environments. This study explores Nafion membrane's IR spectra during soaking and subsequent drying processes in salt solutions at various concentrations. Utilizing the principles of Fick's second law, diffusion coefficients for these processes are derived via exponential approximation. By harnessing machine learning (ML) techniques, including the optimization of neural network hyperparameters via a genetic algorithm (GA) and leveraging various regressors, we effectively pinpointed the optimal model for predicting diffusion coefficients. Notably, for the prediction of soaking coefficients, our model is composed of layers with 64, 64, 32, and 16 neurons, employing ReLU, ELU, sigmoid, and ELU activation functions, respectively. Conversely, for drying coefficients, our model features two hidden layers with 16 and 12 neurons, utilizing sigmoid and ELU activation functions, respectively.

Comparison of Two Methods for Measuring the Temperature Dependence of H2 Permeation Parameters in Nitrile Butadiene Rubber Polymer Composites Blended with Fillers: The Volumetric Analysis Method and the Differential Pressure Method

Hydrogen uptake/diffusivity in nitrile butadiene rubber (NBR) blended with carbon black (CB) and silica fillers was measured with a volumetric analysis method in the 258-323 K temperature range. The temperature-dependent H2 diffusivity was obtained by assuming constant solubility with temperature variations. The logarithmic diffusivity decreased linearly with increasing reciprocal temperature. The diffusion activation energies were calculated with the Arrhenius equation. The activation energies for NBR blended with high-abrasion furnace CB and silica fillers increased linearly with increasing filler content. For NBR blended with medium thermal CB filler, the activation energy decreased with increasing filler content. The activation energy filler dependency is similar to the glass transition temperature filler dependency, as determined with dynamic mechanical analysis. Additionally, the activation energy was compared with that obtained by the differential pressure method through permeability temperature dependence. The same activation energy between diffusion and permeation in the range of 33-39 kJ/mol was obtained, supporting the temperature-independent H2 solubility and H2 physisorption in polymer composites.

Diffusion Coefficients of Variable-Size Amphiphilic Additives in a Glass-Forming Polyethylene Matrix

Diffusion of additives in polymers is an important issue in the plastics industry since migratory-type molecules are widely used to tune the properties of polymeric composites. Predicting the diffusional behavior of new additives can minimize the need for repetitive experiments. This work presents molecular dynamics simulations at the microsecond time scale and uses the MARTINI force field to estimate self-diffusion coefficients, D, of six monounsaturated amides and their analogs carboxylic acids in polyethylene matrices (PE, MW = 5600 Da). The results are strongly influenced by the glass-forming properties of the PE matrix, which we characterize by three distinct temperatures. The metastability region (T < 325 K), the glass transition temperature (Tg = 256-260 K), and the end of the transition (T ≅ 200 K). Self-diffusion mechanisms are inferred from the results of the dependence of D on the molecular mass of the additive, observing a Rouse-like behavior at high temperatures and deviations from it within the metastability region of the matrix. Interestingly, D values are nonsensitive to the nature of the considered polar head for additives of similar size. The temperature-dependent behavior of D follows, at fixed additive size, a linear Arrhenius pattern at high temperatures and a super Arrhenius trend at lower temperatures, which is well represented with a power law equation as predicted by the Mode Coupling Theory (MCT). We offer a conceptual explanation for the observed super-Arrhenius behavior. This explanation draws on Truhlar and Kohen's interpretation of the available energies at both the initial and the transition states along the diffusion pathway. The matrix's mobility significantly affects solute self-diffusion, yielding equal activation enthalpies for the Arrhenius region or the same power law parameters for the super-Arrhenius regime. Finally, we establish a one-to-one time-equivalence of the self-diffusion processes between CG and all-atom systems for the largest additives and the PE matrix in the high-temperature regime.

Organophosphate esters (OPEs) in plastic food packaging: non-target recognition, and migration behavior assessment

Organophosphate esters (OPEs) are widely used as plasticizers in plastic food packaging; however, the migration of OPEs from plastic to food is largely unstudied. We do not even know the specific number of OPEs that exist in the plastic food packaging. Herein, an integrated target, suspect, and nontarget strategy for screening OPEs was optimized using ultrahigh-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). The strategy was used to analyze 106 samples of plastic food packaging collected in Nanjing city, China, in 2020. HRMS allowed full or tentative identification of 42 OPEs, of which seven were reported for the first time. Further, oxidation products of bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite (AO626) in plastics were identified, implying that the oxidation of organophosphite antioxidants (OPAs) could be an important indirect source of OPEs in plastics. The migration of OPEs was examined with four simulated foods. Twenty-six out of 42 OPEs were detected in at least one of the four simulants, particularly isooctane, in which diverse OPEs were detected at elevated concentrations. Overall, the study supplements the list of OPEs that humans could ingest as well as provides essential information regarding the migration of OPEs from plastic food packaging to food.

Modeling extraction of medical device polymers for biocompatibility evaluation

Extraction testing is critical for biocompatibility evaluation of medical devices, whether to generate samples for biological testing or form the basis for toxicological risk assessment. However, it is not always clear how to compare extraction testing between different extraction conditions and sample geometries. We employ a physics-based model to elucidate the theoretical impact of extraction conditions, sample geometry and material properties on extraction efficiency (M/M⁰) and extract concentration (C/C⁰) for single-step and iterative/exhaustive extraction test methods. The model is specified by three parameters: thermodynamic contributions (Ψ), kinetic contributions (τ), and number of extraction iterations (N). We find that over the range of typical parameters for single-step extractions, M/M⁰ only approaches one (complete exhaustion) for relatively large values of Ψ (≥10) and τ(≥1). Further, the model suggests that test article geometry and solvent volume can have a dramatic and sometimes opposing effect on M/M⁰ and C/C⁰. Our results imply that iterative extractions can be approximated as a single-step extraction with scaled parameters Ψ' = ΨN and τ' = τN. The model provides a framework to reduce the biocompatibility evaluation test burden by optimizing test article and extraction condition selection and guiding development of new test protocols.

Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments

Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment's factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO2 evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed.

Systematic evidence on migrating and extractable food contact chemicals: Most chemicals detected in food contact materials are not listed for use

Food packaging is important for today's globalized food system, but food contact materials (FCMs) can also be a source of hazardous chemicals migrating into foodstuffs. Assessing the impacts of FCMs on human health requires a comprehensive identification of the chemicals they contain, the food contact chemicals (FCCs). We systematically compiled the "database on migrating and extractable food contact chemicals" (FCCmigex) using information from 1210 studies. We found that to date 2881 FCCs have been detected, in a total of six FCM groups (Plastics, Paper & Board, Metal, Multi-materials, Glass & Ceramic, and Other FCMs). 65% of these detected FCCs were previously not known to be used in FCMs. Conversely, of the more than 12'000 FCCs known to be used, only 1013 are included in the FCCmigex database. Plastic is the most studied FCM with 1975 FCCs detected. Our findings expand the universe of known FCCs to 14,153 chemicals. This knowledge contributes to developing non-hazardous FCMs that lead to safer food and support a circular economy.

Guidance in selecting analytical techniques for identification and quantification of non-intentionally added substances (NIAS) in food contact materials (FCMS)

There are numerous approaches and methodologies for assessing the identity and quantities of non-intentionally added substances (NIAS) in food contact materials (FCMs). They can give different results and it can be difficult to make meaningful comparisons. The initial approach was to attempt to prepare a prescriptive methodology but as this proved impossible; this paper develops guidelines that need to be taken into consideration when assessing NIAS. Different approaches to analysing NIAS in FCMs are reviewed and compared. The approaches for preparing the sample for analysis, recommended procedures for screening, identification, and quantification of NIAS as well as the reporting requirements are outlined. Different analytical equipment and procedures are compared. Limitations of today's capabilities are raised along with some research needs.

Linear Solvation Energy Relationships (LSERs) for Robust Prediction of Partition Coefficients between Low Density Polyethylene and Water Part I: Experimental Partition Coefficients and Model Calibration

When equilibrium of leaching is reached within a product's duty cycle, partition coefficients polymer/solution dictate the maximum accumulation of a leachable and thus, patient exposure by leachables. Yet, in the pharmaceutical and food industry, exposure estimates based on predictive modeling typically rely on coarse estimations of the partition coefficient, with accurate and robust models lacking. This first part of the study aimed to explore linear solvation energy relationships (LSERs) as high performing models for the prediction of partition coefficients polymer/water. For this, partition coefficients between low density polyethylene (LDPE) and aqueous buffers for 159 compounds spanning a wide range of chemical diversity, molecular weight, vapor pressure, aqueous solubility and polarity (hydrophobicity) were determined and complimentary data collected from the literature (n=159, MW: 32 to 722, logK_i,O/W: -0.72 to 8.61 and logK_i,LDPE/W: -3.35 up to 8.36). The chemical space represented by this compounds set is considered indicative for the universe of compounds potentially leaching from plastics. Based on the dataset for the LDPE material purified by solvent extraction, a LSER model for partitioning between LDPE and water was calibrated to give:logK_i,LDPE/W=-0.529+1.098E_i-1.557S_i-2.991A_i-4.617B_i+3.886V_i. The model was proven accurate and precise (n = 156, R² = 0.991, RMSE = 0.264). Further, it was demonstrated superior over a log-linear model fitted to the same data. Nonetheless, it could be shown that log-linear correlations against logK_i,O/W can be of value for the estimation of partition coefficients for nonpolar compounds exhibiting low hydrogen-bonding donor and/or acceptor propensity. For these nonpolar compounds, the log - linear model was found to be: logK_i,LDPE/W=1.18logK_i,O/W-1.33 (n = 115, R²=0.985, RMSE = 0.313). In contrast, with mono-/bipolar compounds included into the regression data set, an only weak correlation was observed (n = 156, R² = 0.930, RMSE = 0.742) rendering the log-linear model of more limited value for polar compounds. Notably, sorption of polar compounds into native (non-purified) LDPE was found to be up to 0.3 log units lower than into purified LDPE. To identify maximum (i. e. worst-case) levels of leaching in support of chemical safety risk assessments on systems attaining equilibrium before end of shelf-life, it appears adequate to utilize LSER - calculated partition coefficients (in combination with solubility data) by ignoring any kinetical information.

Linear Solvation Energy Relationships (LSERs) for Robust Prediction of Partition Coefficients between Low Desity Polyethylene and Water Part II: Model Evaluation and Benchmarking

By neglecting the kinetics of leaching, the accumulation of leachables in a clinically relevant medium in contact with plastics is principally driven by the equilibrium partition coefficient between the polymer and the medium phase. Based on experimental partition coefficients for a wide set of chemically diverse compounds between low density polyethylene (LDPE) and water, a linear solvation energy relationship (LSER) model was obtained in part I of this study, reading: logK_i,LDPE/W=-0.529+1.098E_i-1.557S_i-2.991A_i-4.617B_i+3.886V_i. The model was proven accurate and precise (n = 156, R2 = 0.991, RMSE = 0.264).) In this part II of the study, for further evaluation and benchmarking of the LSER model ∼ 33% (n = 52) of the total observations were ascribed to an independent validation set. Calculation of partition coefficients logK_i,LDPE/W for this validation set was based on experimental LSER solute descriptors. Linear regression against the corresponding experimental values yielded R2 = 0.985 and RMSE = 0.352. When using LSER solute descriptors predicted from the compound's chemical structure by means of a QSPR prediction tool, instead, R2 = 0.984 and RMSE = 0.511 were obtained. These statistics are considered indicative for extractables with no experimental LSER solute descriptors available. By comparison to LSER models from the literature, a strong correlation between the quality of experimental partition coefficients and the chemical diversity of the training set to the model's predictability was observed, the latter of particular relevance for the application domain of the model. Further, to tentatively match partitioning into LDPE to partitioning into a liquid phase, partition coefficients logK_i,LDPE/W were converted into logK_{i,LDPEamorph/W} by considering the amorphous fraction of the polymer as effective phase volume only. A LSER model now recalibrated based on the observations for logK_{i,LDPEamorph/W} exhibited the constant in the equation above to now read -0.079 instead of -0.529 which rendered the model more similar to a corresponding LSER-model for n-hexadencane/water. Based on LSER system parameters available, the sorption behavior of LDPE could be efficiently compared to the one of polydimethylsiloxane (PDMS), polyacrylate (PA) and polyoxymethylene (POM). The latter, by offering capabilities for polar interactions due to their heteroatomic building blocks, exhibit stronger sorption than LDPE to the more polar, non-hydrophobic domain of sorbates up to an logK_i,LDPE/W range of 3 to 4. Above that range, all four polymers exhibited a roughly similar sorption behavior. Overall, LSERs were found to represent an accurate and user-friendly approach for the estimation of equilibrium partition coefficients involving a polymeric phase. All intrinsic input parameters can be retrieved from a free, web-based and curated database along with the outright calculation of the partition coefficient for any given neutral compound with a known structure for a given two-phased system.

In Silico Prediction of Food Properties: A Multiscale Perspective

Several open software packages have popularized modeling and simulation strategies at the food product scale. Food processing and key digestion steps can be described in 3D using the principles of continuum mechanics. However, compared to other branches of engineering, the necessary transport, mechanical, chemical, and thermodynamic properties have been insufficiently tabulated and documented. Natural variability, accented by food evolution during processing and deconstruction, requires considering composition and structure-dependent properties. This review presents practical approaches where the premises for modeling and simulation start at a so-called “microscopic” scale where constituents or phase properties are known. The concept of microscopic or ground scale is shown to be very flexible from atoms to cellular structures. Zooming in on spatial details tends to increase the overall cost of simulations and the integration over food regions or time scales. The independence of scales facilitates the reuse of calculations and makes multiscale modeling capable of meeting food manufacturing needs. On one hand, new image-modeling strategies without equations or meshes are emerging. On the other hand, complex notions such as compositional effects, multiphase organization, and non-equilibrium thermodynamics are naturally incorporated in models without linearization or simplifications. Multiscale method’s applicability to hierarchically predict food properties is discussed with comprehensive examples relevant to food science, engineering and packaging. Entropy-driven properties such as transport and sorption are emphasized to illustrate how microscopic details bring new degrees of freedom to explore food-specific concepts such as safety, bioavailability, shelf-life and food formulation. Routes for performing spatial and temporal homogenization with and without chemical details are developed. Creating a community sharing computational codes, force fields, and generic food structures is the next step and should be encouraged. This paper provides a framework for the transfer of results from other fields and the development of methods specific to the food domain.

Hazardous metal additives in plastics and their environmental impacts

Historically, many additives and catalysts used in plastics were based on compounds of toxic metals (and metalloids), like arsenic, cadmium, chromium(VI), and lead. Despite subsequent restrictions, hazardous additives remain in plastics in societal circulation because of the pervasiveness of many products and the more general contamination of recycled goods. However, little is understood about their presence and impacts in the environment, with most studies focusing on the role of plastics in acquiring metals from their surroundings through, for example, adsorption. Accordingly, this paper provides a review of the uses of hazardous, metal-based additives in plastics, the relevant European regulations that have been introduced to restrict or prohibit usage in various sectors, and the likely environmental impacts of hazardous additives once plastics are lost in nature. Examination of the literature reveals widespread occurrence of hazardous metals in environmental plastics, with impacts ranging from contamination of the waste stream to increasing the density and settling rates of material in aquatic systems. A potential concern from an ecotoxicological perspective is the diffusion of metals from the matrix of micro- and nanoplastics under certain physico-chemical conditions, and especially favorable here are the acidic environments encountered in the digestive tract of many animals (birds, fish, mammals) that inadvertently consume plastics. For instance, in vitro studies have shown that the mobilization of Cd and Pb from historical microplastics can greatly exceed concentrations deemed to be safe according to migration limits specified by the current European Toy Safety Directive (17 mg kg^-1 and 23 mg kg^-1, respectively). When compared with concentrations of metals typically adsorbed to plastics from the environment, the risks from pervasive, historical additives are far more significant.

The sorption of persistent organic pollutants in microplastics from the coastal environment

Microplastic (MP) pellets were sampled from six sandy beaches around Taiwan in order to investigate the concentrations and compositions of POPs, including: PCDD/Fs, PBDD/Fs, PBDEs, PCBs, PBBs, and their congeners. The concentrations of PCDD/Fs on the surface (C_s) of MP pellets from the six sampling sites were from 1.9 to 14.6 pg∙g^-1, while the overall concentrations within MPs (C_t) were from 95.0 to 1110.6 pg∙g^-1. As PCDD/Fs were adsorbed into the inner part of MPs, a ratio of the total concentrations to surficial concentration of MPs (C_t/C_s) was as high as 355.2 times. The C_t/C_s of other POPs were also significant, such as PBDEs being found up to 8068 times, which could be attributed to artificial addition during manufacturing processes as flame-retardant substances. Primary compositions of PCDD/Fs, PBDD/Fs, and PBDEs on the MPs in our POP congener analysis were all found containing species with higher number of chlorine or bromine, which were adsorbed on the MP surface more easily due to their relative higher K_OW.

Safety of Plastic Food Packaging: The Challenges about Non-Intentionally Added Substances (NIAS) Discovery, Identification and Risk Assessment

Several food contact materials (FCMs) contain non-intentionally added substances (NIAS), and most of the substances that migrate from plastic food packaging are unknown. This review aimed to situate the main challenges involving unknown NIAS in plastic food packaging in terms of identification, migration tests, prediction, sample preparation, determination methods and risk assessment trials. Most studies have identified NIAS in plastic materials as polyurethane adhesives (PU), polyethylene terephthalate (PET), polyester coatings, polypropylene materials (PP), multilayers materials, plastic films, polyvinyl chloride (PVC), recycled materials, high-density polyethylene (HDPE) and low-density polyethylene (LDPE). Degradation products are almost the primary source of NIAS in plastic FCMs, most from antioxidants as Irganox 1010 and Irgafos 168, following by oligomers and side reaction products. The NIAS assessment in plastics FCMs is usually made by migration tests under worst-case conditions using food simulants. For predicted NIAS, targeted analytical methods are applied using GC-MS based methods for volatile NIAS and GC-MS and LC-MS based methods for semi- and non-volatile NIAS; non-targeted methods to analyze unknown NIAS in plastic FCMs are applied using GC and LC techniques combined with QTOF mass spectrometry (HRMS). In terms of NIAS risk assessment and prioritization, the threshold of toxicological concern (TTC) concept is the most applied tool for risk assessment. Bioassays with sensitive analytical techniques seem to be an efficient method to identify NIAS and their hazard to human exposure; the combination of genotoxicity testing with analytical chemistry could allow the Cramer class III TTC application to prioritize unknown NIAS. The scientific justification for implementing a molecular weight-based cut-off (<1000 Da) in the risk assessment of FCMs should be reevaluated. Although official guides and opinions are being issued on the subject, the whole chain's alignment is needed, and more specific legislation on the steps to follow to get along with NIAS.

Using extractables data from single-use components for extrapolation to process equipment-related leachables: The toolbox and justifications

Quantitative information on process equipment-related leachables (PERLs) is required for process qualification and within a safety assessment. Extractables data for single-use equipment are suitable and applicable if the extractables study conditions fit or are bracketing the expected conditions of use. It is necessary to extrapolate extractables data when the expected in-use conditions are not covered by the test conditions. Methods for such quantitative extrapolation of extractables data toward potential PERLs are therefore needed. They are comprehensively described in this publication and include: scaling of extractables data for devices of different sizes adjusted to process-volumes, extrapolation to temperatures different from the extraction temperature, extrapolations to different solvent compositions, extrapolation to various contact times, and the combination of extractables data from individual components to assess assemblies. These extrapolation methods yield extractables data as if an extractables study had been performed. The methods presented are consistently derived from basic physicochemical principles. The relevant, underlying physical parameters are obtained from extractables experiments and are compared with published data. The applicability and justification of the proposed calculation methods are discussed and benchmarked against experimental findings.

Effect of high pressure processing on migration characteristics of polypropylene used in food contact materials

The migration of small molecular mass organic compounds from polypropylene (PP) copolymer films into food simulants during and after high pressure processing (HPP) was studied. An overlapping temperature profile was developed to isolate the pressure effect of HPP (700 MPa, 71°C, 5 min) from equivalent thermal processing (TP) at atmospheric pressure (0.1 MPa). Chloroform, toluene, methyl salicylate, and phenylcyclohexane were chosen as surrogate compounds, and were spiked into test polymer films at concentrations of 762-1152 mg kg^-1 by a solvent soaking technique. Migration (w/w) of surrogate compounds from loaded PP films into Miglyol 812 (a medium-chain triglyceride mixture) and 10% ethanol was quantified by headspace GC/MS during HPP and TP, and subsequent storage at 25°C for up to 10 days. HPP significantly delayed migration of the surrogates from PP into both food simulants relative to TP. The average migrations into Miglyol after TP and HPP were 92.2-109% and 16-60.6%, respectively. Diffusion coefficients estimated by migration modelling showed a reduction of more than two orders of magnitude for all surrogate compounds under high pressure at 700 MPa (AP' = 8.0) relative to equivalent TP at 0.1 MPa (AP' = 13.1). The relative T_g increase of PP copolymer under compression at 700 MPa was estimated as T_g+94°C. For 10% ethanol, average migrations after TP and HPP were 9.3-50.9% and 8.6-22.8%, respectively. During extended storage, migration into both simulants from HPP-treated samples was initially slower than that from untreated or TP-treated films. However, after 8-24 hours of storage, the differences in percent migration of selected surrogates were not significant (p > .05) among the treated PP films. Therefore, the physical changes of PP films that occur during HPP appear to be reversible with a return to their original dimensions and diffusion properties after decompression.

Micro- and nanoplastics - current state of knowledge with the focus on oral uptake and toxicity

The production and use of plastics has constantly increased over the last 30 years. Over one third of the plastics is used in disposables, which are discarded within three years of their production. Despite efforts towards recycling, a substantial volume of debris has accumulated in the environment and is slowly degraded to micro- and nanoplastics by weathering and aging. It has recently been discovered that these small particles can enter the food chain, as for example demonstrated by the detection of microplastic particles in honey, beer, salt, sea food and recently in mineral water. Human exposure has further been documented by the detection of plastic microparticles in human feces. Potential toxic consequences of oral exposure to small plastic particles are discussed. Due to lacking data concerning exposure, biodistribution and related effects, the risk assessment of micro- and nanoplastics is still not possible. This review focuses on the oral uptake of plastic and polymer micro- and nanoparticles. Oral exposure, particle fate, changes of particle properties during ingestion and gastrointestinal digestion, and uptake and transport at the intestinal epithelium are reviewed in detail. Moreover, the interaction with intestinal and liver cells and possibly resulting toxicity are highlighted.

Modeling in food across the scales: towards a universal mass transfer simulator of small molecules in food

Multiscale modeling in food is the cutting-edge strategy to revisit food structure and food composition to meet specific targets such as bioavailability, oral perception, or to evaluate the contamination of food by chemicals. A special implementation of Langevin dynamics is proposed to describe mass transfer in structured food. The concepts of random walks over discrete times and physicochemical interactions are connected via an exact solution of the Fokker–Planck equation across interfaces. The methodology is illustrated on the calculation of effective diffusivities of small solutes in emulsions in relationship with their polydispersity, the volume fraction of dispersed phase d = [0.1, 0.4], the ratio of diffusion coefficients between the two phases, rD = [10−2, 102], and the partition coefficients between the continuous and disperse phases, K = [10−2, + ∞[. Simulated diffusion paths are detailed in 2D emulsions and the effective diffusivities compared with the core–shell model of Kalnin and Kotomin (J Phys A Math Gen 31(35):7227–7234, 1998). The same effects are finally tabulated for 3D emulsions covering the full range of food applications. The methodology is comprehensive enough to enable various extensions such as chemisorption, adsorption in the surfactant layer, local flows, flocculation/creaming.

Uptake and Release Kinetics of Organic Contaminants Associated with Micro- and Nanoplastic Particles

A generic theoretical framework is presented for describing the kinetics of uptake and release of organic compounds that associate with plastic particles. The underlying concepts account for the physicochemical features of the target organic compounds and the plastic particles. The developed framework builds on concepts established for dynamic speciation analysis by solid-phase microextraction and the size-dependent reactivity features of particulate complexants. The theoretical framework is applied to interpretation of literature data, thereby providing more rigorous insights into previous observations. The presented concepts enable predictions of the sink/source functioning of plastic particles and their impact on the dynamic chemical speciation of organic compounds in aqueous environmental media and within biota. Our results highlight the fundamental influence of particle size on the uptake and release kinetics. The findings call for a comprehensive description of the physicochemical features of plastic particles to be provided in experimental studies on micro- and nanoplastics in different types of aquatic environmental media.

Synthesis of Polylactic Acid Initiated through Biobased Antioxidants: Towards Intrinsically Active Food Packaging

Polylactide (PLA)-based polymers, functionalized with biobased antioxidants, were synthesized, to develop an intrinsically active, biobased and potentially biodegradable material for food packaging applications. To achieve this result, phenolic antioxidants were exploited as initiators in the ring opening polymerization of l-lactide. The molecular weight, thermal properties and in vitro radical scavenging activity of the polymers obtained were compared with the ones of a PLA Natureworks 4043D, commonly used for flexible food packaging applications. The most promising synthesized polymer, bearing vanillyl alcohol as initiator (PLA-VA), was evaluated for active food packaging applications. Packaging with PLA-VA films reduced color and fat oxidation of salami during its shelf life.

A regression-based model to predict chemical migration from packaging to food

Packaging materials can be a source of chemical contaminants in food. Process-based migration models (PMM) predict the chemical fraction transferred from packaging materials to food (F_C) for application in prioritisation tools for human exposure. These models, however, have a relatively limited applicability domain and their predictive performance is typically low. To overcome these limitations, we developed a linear mixed-effects model (LMM) to statistically relate measured F_C to properties of chemicals, food, packaging, and experimental conditions. We found a negative relationship between the molecular weight (MW) and F_C, and a positive relationship with the fat content of the food depending on the octanol-water partitioning coefficient of the migrant. We also showed that large chemicals (MW > 400 g/mol) have a higher migration potential in packaging with low crystallinity compared with high crystallinity. The predictive performance of the LMM for chemicals not included in the database in contact with untested food items but known packaging material was higher (Coefficient of Efficiency (CoE) = 0.21) compared with a recently developed PMM (CoE = -5.24). We conclude that our empirical model is useful to predict chemical migration from packaging to food and prioritise chemicals in the absence of measurements.

A blob model to parameterize polymer hole free volumes and solute diffusion

Solute diffusion in solid polymers has tremendous applications in packaging, reservoir, and biomedical technologies but remains poorly understood. Diffusion of non-entangled linear solutes with chemically identical patterns (blobs) deviates dramatically in polymers in the solid-state (α_lin > 1, Macromolecules 2013, 46, 874) from their behaviors in the molten state (α_lin = 1, Macromolecules, 2007, 40, 3970). This work uses the scale invariance of the diffusivities, D, of linear probes D(N·M_blob + M_anchor,T,T_g) = N^{-α_lin(T,T_g)}D(M_blob + M_anchor,T,T_g) comprising N identical blobs of mass M_blob and possibly one different terminal pattern (anchor of mass M_anchor) to evaluate the amounts of hole-free volume in seven polymers (aliphatic, semi-aromatic and aromatic) over a broad range of temperatures (-70 K ≤T-T_g≤ 160 K). The new parameterization of the concept of hole-free volumes opens the application of the free-volume theory (FVT) developed by Vrentas and Duda to practically any polymer, regardless of the availability of free-volume parameters. The quality of the estimations was tested with various probes including n-alkanes, 1-alcohols, n-alkyl acetates, and n-alkylbenzene. The effects of enthalpic and entropic effects of the blobs and the anchor were analyzed and quantified. Blind validation of the reformulated FVT was tested successfully by predicting from first principles the diffusivities of water and toluene in amorphous polyethylene terephthalate from 4 °C to 180 °C and in various other polymers. The new blob model would open the rational design of additives with controlled diffusivities in thermoplastics.

Empirical models to predict the effect of sterilisation and storage on bisphenols migration from metallic can coatings into food simulants

Based on response surface methodology, empirical models were built to predict the influence of can processing (heat treatment) and storage conditions (time and temperature) on the migration of bisphenol compounds from the inner lacquer of tinplate cans (4 brands) into several food simulants. Analysis using liquid chromatography revealed the presence of BADGE.2H₂O and BPA in all samples. Models were significant in fitting the levels of these two bisphenols in food simulants depending on the input variables, with excellent adjusted coefficients of determination. Their prediction performance was validated through running new data sets. Further comparison of predicted values with bisphenols levels measured in canned vegetables revealed that the proposed models are conservative. By the desirability of the response output, the models are capable of proposing the range of can processing and storage conditions that limit migration for further compliance with the regulation. The proposed approach could be a convenient tool for the industries to control processing conditions in order to ensure the conformity of canned foods.

The Ubiquitous Issue of Cross-Mass Transfer: Applications to Single-Use Systems

The leaching of chemicals by materials has been integrated into risk management procedures of many sectors where hygiene and safety are important, including food, medical, pharmaceutical, and biotechnological applications. The approaches focus on direct contact and do not usually address the risk of cross-mass transfer of chemicals from one item or object to another and finally to the contacting phase (e.g., culture medium, biological fluids). Overpackaging systems, as well as secondary or ternary containers, are potentially large reservoirs of non-intentionally added substances (NIAS), which can affect the final risk of contamination. This study provides a comprehensive description of the cross-mass transfer phenomena for single-use bags along the chain of value and the methodology to evaluate them numerically on laminated and assembled systems. The methodology is validated on the risk of migration i) of ϵ-caprolactam originating from the polyamide 6 internal layer of the overpackaging and ii) of nine surrogate migrants with various volatilities and polarities. The effects of imperfect contacts between items and of an air gap between them are particularly discussed and interpreted as a cutoff distance depending on the considered substance. A probabilistic description is suggested to define conservative safety-margins required to manage cross-contamination and NIAS in routine.

Strategies for Rapid Risk Assessment of Color Additives Used in Medical Devices

Many polymeric medical devices contain color additives for differentiation or labeling. Although some additives can be toxic under certain conditions, the risk associated with the use of these additives in medical device applications is not well established, and evaluating their impact on device biocompatibility can be expensive and time consuming. Therefore, we have developed a framework to conduct screening-level risk assessments to aid in determining whether generating color additive exposure data and further risk evaluation are necessary. We first derive tolerable intake values that are protective for worst-case exposure to 8 commonly used color additives. Next, we establish a model to predict exposure limited only by the diffusive transport of the additive through the polymer matrix. The model is parameterized using a constitutive model for diffusion coefficient (D) as a function of molecular weight (Mw) of the color additive. After segmenting polymer matrices into 4 distinct categories, upper bounds on D(Mw) were determined based on available data for each category. The upper bounds and exposure predictions were validated independently to provide conservative estimates. Because both components (toxicity and exposure) are conservative, a ratio of tolerable intake to exposure in excess of one indicates acceptable risk. Application of this approach to typical colored polymeric materials used in medical devices suggests that additional color additive risk evaluation could be eliminated in a large percentage (≈90%) of scenarios.

Potential of Liquid Extraction Surface Analysis Mass Spectrometry (LESA-MS) for the Characterization of Polymer-Based Materials

Liquid extraction surface analysis mass spectrometry (LESA -MS) is a direct analysis method suitable for the analysis of polymers. It is based on a fast and efficient extraction of polymer components, such as non-intentionally added species (NIAS), post-polymerization residues, or additives, and residues resulting from specific uses followed by their MS detection. In comparison with batch methods, it is a “green” method, using negligible volumes of organic solvents, and it is cost-effective, avoiding lengthy sample preparation procedures. It can be used for the detection of known molecules (targeted analysis), identification of unknown species (exploratory analysis requiring MS/MS) and semi-quantative analysis, if standards are available. The to-date applications of LESA-MS in the field of polymer science are reviewed and critically discussed taking into account the hands-on experience from the authors’ laboratory. Future possibilities of LESA applications are highlighted.

Migration studies of butylated hydroxytoluene, tributyl acetylcitrate and dibutyl phthalate into food simulants

BACKGROUND

Migration is a mass transfer process in which chemical substances with a low molecular weight are transferred from packaging into food. This phenomenon has received great attention from a food safety point of view because these chemicals could potentially represent a risk for consumers' health. The present study investigated the process of migration of two common plasticizers [tributyl acetylcitrate (ATBC) and dibutyl phthalate (DBP)] and one antioxidant [butylated hydroxytoluene (BHT)] from a common plastic material used in food packaging (low density polyethylene) into 50% ethanol (v/v), 95% ethanol (v/v) and isooctane. A mathematical model based on Fick's second law was used to determine the partition and diffusion coefficients. In addition, the effect of temperature on the diffusion was studied by applying the Arrhenius equation.

RESULTS

High-performance liquid chromatography with diode-array detection and gas chromatography-mass spectrometry methods were applied to measure the amount of ATBC, DBP and BHT that migrated into the food simulants. A mathematical model based on Fick's second law of diffusion was used to estimate key migration parameters: diffusion and partition coefficients (D_P and K_P/F ), which were determined for each migrant and food simulant at three temperatures (10, 20 and 40 °C). The results showed that the diffusion process is significantly influenced by temperature, although the type of simulant also plays an important role in the migration process.

CONCLUSION

The model investigated is shown to be appropriate for predicting the migration from food packaging into real foodstuffs at common storage temperatures. © 2018 Society of Chemical Industry.

The physical chemistry of odors - Consequences for the work with detection dogs

Search dogs are used throughout the world in the search for illicit compounds or human individuals and similar tasks. Such search work is complex and not well understood in all its details which makes training of the dogs difficult. One important component for a successful education and deployment of search dogs is a good understanding of the behavior of scents under typical environmental conditions. This work summarizes up-to-date knowledge on the physico-chemistry of scents and discusses the consequences for the every-day work of dog handlers and trainers.

Application of Experimental Polystyrene Partition Constants and Diffusion Coefficients to Predict the Sorption of Neutral Organic Chemicals to Multiwell Plates in in Vivo and in Vitro Bioassays

Sorption to the polystyrene (PS) of multiwell plates can affect the exposure to organic chemicals over time in in vitro and in vivo bioassays. Experimentally determined diffusion coefficients in PS ( D_PS) were in a narrow range of 1.25 to 8.0 · 10^-16 m² s^-1 and PS-water partition constants ( K_PS/w) ranged from 0.04 to 5.10 log-units for 22 neutral organic chemicals. A kinetic model, which explicitly accounts for diffusion in the plastic, was applied to predict the depletion of neutral organic chemicals from different bioassay media by sorption to various multiwell plate formats. For chemicals with log K_ow > 3, the medium concentrations decreased rapidly and considerably in the fish embryo toxicity assay but medium concentrations remained relatively constant in the cell-based bioassays with medium containing 10% fetal bovine serum (FBS), emphasizing the ability of the protein- and lipid-rich medium to compensate for losses by multiwell plate sorption. The PS sorption data may serve not only for exposure assessment in bioassays but also to model the contaminant uptake by and release from plastic packaging material and the chemical transport by PS particles in the environment.

An untargeted evaluation of food contact materials by flow injection analysis-mass spectrometry (FIA-MS) combined with independent components analysis (ICA)

Food contact materials (FCMs), especially plastics, are known to be a potential source of contaminants in food. In fact, various groups of additives are used to protect the integrity of the material during processing and life time. However, these intentionally added substances (IAS) could also lead to degradation products called non-intentionally added substances (NIAS), due to reactions occurring in the polymeric material. Complex mixtures of components may therefore be generated within the material, creating a source of potential migrating substances towards food in contact. In this context, an innovative analytical approach is proposed in order to assess IAS and NIAS in plastic FCMs for a fast screening of their composition. For this purpose, solvent extracts of polyethylene (PE) pellets, containers and films were analyzed by flow injection analysis-mass spectrometry (FIA-MS). This direct approach offers the ability to perform a large number of analyses in a short time. Mass spectral fingerprints were then treated by a multivariate data analysis technique called independent components analysis (ICA) in order to overcome the complexity of such data and to highlight hidden information related to IAS and NIAS molecules. ICA applied on mass spectral fingerprints of PE extracts highlighted group discriminations related to different m/z values which were putatively assigned to IAS and also to NIAS. In order to confirm these putative annotations, a hybrid LTQ-Orbitrap was used for high resolution mass spectrometry analysis. Moreover, MS/MS experiments were performed on some discriminant ions to improve their putative identification. The proposed methodology combining FIA-MS fingerprints and ICA proved its efficiency in identifying IAS and NIAS in plastic FCMs and its capability to discriminate different PE samples, in a relatively fast approach compared to classical analytical techniques. This approach may help the FCMs classification for compounders in the selection of the starting substances in plastic formulation and for plastic converters in the control of manufacturing processes as well as for the monitoring of final products.

Preliminary quantification of the permeability, solubility and diffusion coefficients of major aroma compounds present in herbs through various plastic packaging materials

BACKGROUND

Aroma permeation through packaging material is an important factor when designing a package for food products. The masses of aroma compounds permeating through films over time were measured at 25 °C using a quasi-isostatic system. A model was proposed for estimating the permeability coefficients (P) of key aroma compounds present in fresh herbs (i.e. eucalyptol, estragole, linalool and citral) through major plastic films used by the food industry [i.e. low-density polyethylene (LDPE), polypropylene (PP), nylon (Nylon), polyethylene terephthalate (PET), metalised-polyethylene terephthalate (MPET) and poly(lactic acid) (PLA)]. Solubility coefficients (S) were estimated from the amount of aroma compound sorbed in the films. Diffusion coefficients (D) were estimated following from the relation P = D*S.

RESULTS

P and D for all four aroma compounds were highest in LDPE, except for eucalyptol, which P was slightly higher in PLA. The solubility coefficients and contact angles were highest in PLA suggesting the highest affinity of PLA to these aroma compounds. The theoretical solubility parameters were correlated with the solubility coefficients for estragole and citral, but not for eucalyptol and linalool.

CONCLUSION

The preliminary P, D and S of eucalyptol, estragole, linalool and citral through LDPE, PP, Nylon, PET, MPET and PLA can be useful in selecting the proper packaging material for preserving these specific aroma compounds in food products and can potentially be used for estimating the shelf life of food products based on aroma loss. © 2017 Society of Chemical Industry.

Project SafeFoodPack Design: case study on indirect migration from paper and boards

Migration due to indirect contact with packaging caused several major sanitary crises, including the spread contamination of dry food by mineral oils and printing ink constituents from cardboard. The issues are still not fully resolved because the mechanisms have been insufficiently described and the relationship between design, contamination level, type of contaminant, and conditions of storage (time and temperature) are poorly understood. This study proposes a forensic analysis of these phenomena when food is separated from cardboard by a plastic layer. Practical relationships and advanced simulation scenarios were devised and validated against the long-term migration between 20 and 60°C of 15 substances. They were chosen to be representative of the main contaminants of cardboard: aliphatic and aromatic mineral oils, photo-initiators and plasticisers. Data were summarised as iso-contamination curves and iso-contamination times up to 2 years. Simple rules are illustrated to extrapolate the results to arbitrary conditions in order to identify critical substances and to estimate the plastic film's thickness to keep the contamination within acceptable limits. Recommendations for the risk management of contamination routes without contact are finally drafted.