Prediction of Partition Coefficients of Plastic Additives between Packaging Materials and Food Simulants

PredicDiff™: a computational tool for the prediction of PERLs concentrations based on extractables data

PredicDiff™, a computational modeling tool that allows fitting diffusion curves to process equipment related leachables (PERLs) is presented. Based on the measurement of extractables (analytical data), Fick's second law of diffusion, and a Trust Region Rebounds based fitting algorithm (optimize.curve_fit from Scipy), the Python-based model fits a diffusion curve to each extractable/PERL thus allowing the determination of the PERL amount after any arbitrary contact time and temperature for example, the actual production conditions. In addition, PredicDiff™ delivers the system's diffusion- and partition coefficients and the equilibrium concentration. Three case studies are presented: 1) interpolation of ε-caprolactam from a polysulfone disconnector from 24h to 2h, 2) adjustment of the diffusion of ε-caprolactam from a polysulfone disconnector from 40°C to 21°C, and 3) extrapolation of 2,4-Di-tert-butylphenol from an ultra-low-density polyethylene (ULDPE) bag from 70 to 90 days. In addition, the usability of PredicDiff™ for inter- or extrapolation of an unidentified extractable from a silicone tubing is shown. In the first case, after a contact time of 2h, the concentration and hence, also patient exposure to ε-caprolactam is reduced by 70% in comparison to the extractable value after 24h. In the second case, further adjustment based on contact temperature (21°C vs. 40°C) gives a total reduction of 87%. In the third case, the concentration and therefore, also patient exposure to 2,4-Di-tert-butylphenol increases by 2.6% if storage is prolonged from 70 days to 90 days. PredicDiff™ has no limitations on the types of extractables (including those whose identities are not elucidated) or concentration ranges. Based on the remodeling of diffusion curves from literature and the calculation of extractables amounts from studies (analytical data), it is shown that PredicDiff™ provides reliable results within an acceptable range of uncertainty. Inter- and extrapolated PERLs can support the extractables and leachables (E&L) risk management by quickly calculating a more realistic concentration and ultimately, patient exposure.

Distinguishing between extractable and leachable contents of styrene oligomers in various polystyrene consumer products: Towards environmentally realistic scenarios

Plastic additives' environmental impacts remain insufficiently understood due to knowledge gaps in their bioavailability, despite growing concerns from increased plastic use and waste. Additives that are non-covalently bound but strongly interact with polymers can be extractable but not leachable, thus non-bioavailable. Nevertheless, most studies have not distinguished between extractable (EC) and leachable content (LC) in plastic additives. We quantified the EC and LC of styrene oligomers (SOs) in polystyrene (PS) by applying the selective solvent compatibility of PS-dissolution in dichloromethane for EC and swelling in n-hexane for LC. Significant differences were found between EC and LC of SOs in 28 widely consumed PS products and across three PS types-expanded PS (EPS), extruded PS (XPS), and solid PS. EPS showed lower EC and LC values and fewer SO isomers. LCs were only 32 % (EPS), 84 % (XPS), and 72 % (solid PS) of ECs, suggesting bioavailable fractions may be overestimated if only EC is considered. We estimate that 3.3 MT of PS-incorporated SOs, with 76 % in leachable forms, have entered the environment, but much may still remain in PS debris. Distinct isomer ratios and high non-leachable fractions in EPS suggest that SOs could serve as effective tracers for distinguishing and quantifying invisible EPS-origin particles in beach sediments. This study underscores the need to differentiate EC from LC for environmentally realistic risk assessment and source identification.

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.

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.

Challenges and opportunities of solvent-based additive extraction methods for plastic recycling

Additives are ubiquitously used in plastics to improve their functionality. However, they are not always desirable in their 'second life' and are a major bottleneck for chemical recycling. Although research on extraction techniques for efficient removal of additives is increasing, it resembles much like uncharted territory due to the broad variety of additives, plastics and removal techniques. Today solvent-based additive extraction techniques, solid-liquid extraction and dissolution-precipitation, are considered to be the most promising techniques to remove additives. This review focuses on the assessment of these techniques by making a link between literature and physicochemical principles such as diffusion and Hansen solubility theory. From a technical point of view, dissolution-precipitation is preferred to remove a broad spectrum of additives because diffusion limitations affect the solid-liquid extraction recoveries. Novel techniques such as accelerated solvent extraction (ASE) are promising for finding the balance between these two processes. Because of limited studies on the economic and environmental feasibility of extraction methods, this review also includes a basic economic and environmental assessment of two extreme cases for the extraction of additives. According to this assessment, the feasibility of additives removal depends strongly on the type of additive and plastic and also on the extraction conditions. In the best-case scenario at least 70% of solvent recovery is required to extract plasticizers from polyvinyl chloride (PVC) via dissolution-precipitation with tetrahydrofuran (THF), while solid-liquid extraction of phenolic antioxidants and a fatty acid amide slip agents from polypropylene (PP) with dichloromethane (DCM) can be economically viable even without intensive solvent recovery.

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.

Molecular thermodynamics for food science and engineering

We argue that thanks to molecular modeling approaches, many thermodynamic properties required in Food Science and Food Engineering will be calculable within a few hours from first principles in a near future. These new possibilities will enable to bridge via multiscale modeling composition, process and storage effects to reach global optimization, innovative concepts for food or its packaging. An outlook of techniques and a series of examples are given in this perspective. We emphasize solute chemical potentials in polymers, liquids and their mixtures as they cannot be understood and estimated without theory. The presented atomistic and coarse-grained methods offer a natural framework to their conceptualization in polynary systems, entangled or crosslinked homo- or heteropolymers.

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.

Predicting diffusion coefficients of chemicals in and through packaging materials

Most of the physicochemical properties in polymers such as activity and partition coefficients, diffusion coefficients, and their activation with temperature are accessible to direct calculations from first principles. Such predictions are particularly relevant for food packaging as they can be used (1) to demonstrate the compliance or safety of numerous polymer materials and of their constitutive substances (e.g. additives, residues…), when they are used: as containers, coatings, sealants, gaskets, printing inks, etc. (2) or to predict the indirect contamination of food by pollutants (e.g. from recycled polymers, storage ambiance…) (3) or to assess the plasticization of materials in contact by food constituents (e.g. fat matter, aroma…). This review article summarizes the classical and last mechanistic descriptions of diffusion in polymers and discusses the reliability of semi-empirical approaches used for compliance testing both in EU and US. It is concluded that simulation of diffusion in or through polymers is not limited to worst-case assumptions but could also be applied to real cases for risk assessment, designing packaging with low leaching risk or to synthesize plastic additives with low diffusion rates.

Influence of deep frying on the unsaponifiable fraction of vegetable edible oils enriched with natural antioxidants

The influence of deep frying, mimicked by 20 heating cycles at 180 °C (each cycle from ambient temperature to 180 °C maintained for 5 min), on the unsaponifiable fraction of vegetable edible oils represented by three characteristic families of compounds (namely, phytosterols, aliphatic alcohols, and triterpenic compounds) has been studied. The target oils were extra virgin olive oil (with intrinsic content of phenolic antioxidants), refined sunflower oil enriched with antioxidant phenolic compounds isolated from olive pomace, refined sunflower oil enriched with an autoxidation inhibitor (dimethylpolysiloxane), and refined sunflower oil without enrichment. Monitoring of the target analytes as a function of both heating cycle and the presence of natural antioxidants was also evaluated by comparison of the profiles after each heating cycle. Identification and quantitation of the target compounds were performed by gas cromatography-mass spectrometry in single ion monitoring mode. Analysis of the heated oils revealed that the addition of natural antioxidants could be an excellent strategy to decrease degradation of lipidic components of the unsaponifiable fraction with the consequent improvement of stability.