A comprehensive two-scale model for predicting the oxidizability of fatty acid methyl ester mixtures.

The intricate mechanisms of oil thermooxidation and their accurate prediction have long been hampered by the combinatory nature of propagation and termination reactions involving randomly generated radicals. To unravel this complexity, we suggest a two-scale mechanistic description that connects the chemical functions (scale 1) with the molecular carriers of these functions (scale 2). Our method underscores the importance of accounting for cross-reactions between radicals in order to fully comprehend the reactivities in blends. We rigorously tested and validated the proposed two-scale scheme on binary and ternary mixtures of fatty acid methyl esters (FAMEs), yielding three key insights: (1) The abstraction of labile protons hinges on the carrier, defying the conventional focus on hydroperoxyl radical types. (2) Termination reactions between radicals adhere to the geometric mean law, exhibiting symmetric collision ratios. (3) The decomposition of hydroperoxides emerges as a monomolecular process above 80 °C, challenging the established combinatorial paradigm. Applicable across a wide temperature range (80 °C to 200 °C), our findings unlock the production of blends with controlled thermooxidation stability, optimizing the use of vegetable oils across applications: food science, biofuels, and lubricants.

Computer-aided food engineering.

Computer-aided food engineering (CAFE) can reduce resource use in product, process and equipment development, improve time-to-market performance, and drive high-level innovation in food safety and quality. Yet, CAFE is challenged by the complexity and variability of food composition and structure, by the transformations food undergoes during processing and the limited availability of comprehensive mechanistic frameworks describing those transformations. Here we introduce frameworks to model food processes and predict physiochemical properties that will accelerate CAFE. We review how investments in open access, such as code sharing, and capacity-building through specialized courses could facilitate the use of CAFE in the transformation already underway in digital food systems.

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 (αlin > 1, Macromolecules 2013, 46, 874) from their behaviors in the molten state (αlin = 1, Macromolecules, 2007, 40, 3970). This work uses the scale invariance of the diffusivities, D, of linear probes D(N·Mblob + Manchor,T,Tg) = N-αlin(T,Tg)D(Mblob + Manchor,T,Tg) comprising N identical blobs of mass Mblob and possibly one different terminal pattern (anchor of mass Manchor) 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-Tg≤ 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.

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.

Rational Design of Packaging: Toward Safer and Ecodesigned Food Packaging Systems.

It is necessary and urgent to reduce the impact of single-use plastics and in particular those used for beverages and similar products. Fewer plastics or reduced shelf-life need to be explored simultaneously while keeping open the possibilities of bringing on the innovative market designs and consumer experiences. This work details a general computational framework bridging simulation of coupled mass transfer and non-linear thermodynamics with 3D geometry optimization, ecodesign and other mass transfer-related risks (collapse, migration of chemicals). The three-dimensions (impacts, design, shelf-life) of the storage of alcoholic beverages in plastic containers are presented as a representative case-study of the multi-objective ecodesign problem and as an illustration of new trends to accelerate prototyping and innovation. The capacity to evaluate, maximize product shelf-life and minimize packaging waste was tested on 450 miniatures served usually in plane and train. Four alcoholic strengths (including pure water) and four storage conditions were considered. Several alternatives (900 different 3D designs) were explored by simulation and constrained optimization to reach the targeted shelf-life. The large set was used to establish the Pareto optimal design enabling to minimize weights while maximizing shelf-life. The approach is sufficiently versatile and flexible to adapt arbitrary designs and additional phenomena controlling shelf-life (aroma scalping, oxidation, migration of non-intentionally added substances).

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.

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.

Local demixion in plasticized polylactide probed by electron spin resonance.

Improving the barrier properties to gas and organic compounds of biosourced polyesters, such as polylactides (PLAs), by increasing their crystallinity has been suggested by several authors. This paper investigates the risk of microphase separation for a technological approach that would involve a plasticization of PLA, to further its crystallization kinetics, with common plasticizers: Acetyl tributyl citrate (ATBC) and Poly(ethylene glycol) (PEG). Overplasticization effects following microphase separation were monitored along the film thickness by exposing dynamically thermo-compressed films to nitroxide spin-probes. The method enabled a scan of the local polymer mobility for different concentration profiles in spin-probes, with in particular a maximum moving continuously in time towards the geometric center. The results were interpreted as excess local temperatures that would give similar ESR spectra motion in the bulk. It was shown that measured excess temperatures could be related to local shifts in the glass transition temperature along the film thickness.

Consumer exposure to substances in plastic packaging. I. Assessment of the contribution of styrene from yogurt pots.

A generic methodology for the assessment of consumer exposure to substances migrating from packaging materials into foodstuffs during storage is presented. Consumer exposure at the level of individual households is derived from the probabilistic modeling of the contamination of all packed food product units (e.g. yogurt pot, milk bottle, etc.) consumed by a given household over 1 year. Exposure of a given population is estimated by gathering the exposure distributions of individual households to suitable weights (conveniently, household sizes). Calculations are made by combining (i) an efficient resolution of migration models and (ii) a methodology utilizing different sources of uncertainty and variability. The full procedure was applied to the assessment of consumer exposure to styrene from yogurt pots based on yearly purchase data of more than 5400 households in France (about 2 million yogurt pots) and an initial concentration c0 of styrene in yogurt pot walls, which is assumed to be normally distributed with an average value of 500 mg kg-1 and a standard deviation of 150 mg kg-1. Results are discussed regarding both sensitivity of the migration model to boundary conditions and household practices. By assuming a partition coefficient of 1 and a Biot number of 100, the estimated median household exposure to styrene ranged between 1 and 35 microg day-1 person-1 (5th and 95th percentiles) with a likely value of 12 microg day-1 person-1 (50th percentile). It was found that exposure does not vary independently with the average consumption rate and contact times. Thus, falsely assuming a uniform contact time equal to the sell-by-date for all yogurts overestimates significantly the daily exposure (5th and 95th percentiles of 2 and 110 microg day-1 person-1, respectively) since high consumers showed quicker turnover of stock.

Contamination of packaged food by substances migrating from a direct-contact plastic layer: Assessment using a generic quantitative household scale methodology.

The contamination risk in 12 packaged foods by substances released from the plastic contact layer has been evaluated using a novel modeling technique, which predicts the migration that accounts for (i) possible variations in the time of contact between foodstuffs and packaging and (ii) uncertainty in physico-chemical parameters used to predict migration. Contamination data, which are subject to variability and uncertainty, are derived through a stochastic resolution of transport equations, which control the migration into food. Distributions of contact times between packaging materials and foodstuffs were reconstructed from the volumes and frequencies of purchases of a given panel of 6422 households, making assumptions about household storage behaviour. The risk of contamination of the packaged foods was estimated for styrene (a monomer found in polystyrene yogurt pots) and 2,6-di-tert-butyl-4-hydroxytoluene (a representative of the widely used phenolic antioxidants). The results are analysed and discussed regarding sensitivity of the model to the set parameters and chosen assumptions.