The partition coefficients of n-alkanes, n-alcohols, volatiles, and typical antioxidants between a low density polyethylene and several alcohols (methanol and ethanol) were predicted without fitting variables using an off-lattice Flory-Huggins approach. The main advantage of the proposed excluded volume constraint method was to sample at atomistic scale pairwise contact energies and the residual entropic contribution due to possible different conformers and reorientations. The positional entropy was considered both in the polymer and in the liquid as in the original Flory-Huggins theory. Possible biases due to the formulation and conformational sampling were analyzed for molecules different in size, in shape, and in stiffness. The predictions were close to the experimental uncertainty on the partition coefficients between the amorphous part of the polymer and the tested liquids. The present work confirmed that plastic additives, which are by design highly compatible with the polymer, had also a significant chemical affinity with polar liquids consisting of smaller molecules. Finally, a general predictive model of partition coefficients based on solubility coefficients was proposed.

Partition coefficients, K i,F/P , between liquids or food simulants, F, and amorphous regions of polymers, P, are important quantities to predict the sorption or desorption kinetics in various areas and in particular to predict the contamination of food by substances originating from food contact materials. This work extends an atomistic Flory-Huggins approach previously developed by us (Ind. Eng. Chem. Res 2009, 48, 5285-5301) to predict K i,F/P values for large solutes such as antioxidants, light stabilizers, and surface agents. Two extensions were particularly considered. The first extension aims at determining by isobaric molecular dynamics (MD) simulation the contribution of translational entropy in liquids with increasing polarity (isopropanol, ethanol, methanol, ethyl acetate, water) for large and flexible solutes representative of plastics additives. It was found to be higher than the partial molar volume of such solutes, independent of the considered alcohol and satisfactory estimated by the volume accessible to a hydrogen probe. The validity of the coarse-graining approximation for large flexible solutes (octadecane and octacosane) was tested by computing the radial distribution function from MD simulations. A simple correction was proposed to account for the partial overlapping at the coarsegrained level between F molecules and large flexible segments of solutes. The second major improvement extends the whole methodology to water and water-ethanol mixtures. Intrinsic limitations of the Flory-Huggins approximation to handle hydrogen bond cooperativity were overcame by reweighting contact energies in water and by introducing tabulated nonideal properties of water-ethanol mixtures. All predictions agreed well with previously published partitioning data as well as those generated by this study. From experimental values and theoretical considerations, the possibility to predict the contamination of food emulsions with water-ethanol mixtures is finally discussed.

Emulsifier free emulsion was developed with a new patented technique for food and cosmetic applications. This emulsification process dispersed oil droplets in water without any emulsifier. Emulsions were prepared with different vegetable oil ratios 5%, 10% and 15% (v/v) using high frequency ultrasounds generated by piezoelectric ceramic transducer vibrating at 1.7 MHz. The emulsion was prepared with various emulsification times between 0 and 10h. Oil droplets size was measured by laser granulometry. The pH variation was monitored; electrophoretic mobility and conductivity variation were measured using Zêtasizer equipment during emulsification process. The results revealed that oil droplets average size decreased significantly (p<0.05) during the first 6h of emulsification process and that from 160 to 1 μm for emulsions with 5%, 10% and from 400 to 29 μm for emulsion with 15% of initial oil ratio. For all tested oil ratios, pH measurement showed significant decrease and negative electrophoretic mobility showed the accumulation of OH(-) at oil/water interface leading to droplets stability in the emulsion. The conductivity of emulsions showed a decrease of the ions quantity in solution, which indicated formation of positive charge layer around OH(-) structure. They constitute a double ionic layer around oil particles providing emulsion stability. This study showed a strong correlation between turbidity measurement and proportion of emulsified oil.

The desorption of additives and polymer residues from materials (P) is of significant concern for a wide range of applications, including polymer ageing, off-odors, and the safety of materials in contact with food or water. With diffusion coefficients, partition coefficients between P and hydrogen-bonding liquids (L), denoted K i , L/P for a solute i, are fundamental quantities to assess the loss of plastics constituents. For a polymer with a crystallinity c, they are defined as ln(K i , L/P ) -ln(1-c) =(uexi,P-uexi,L)/(kBT), where {uexi,k}k=L,P are the excess chemical potentials and where kB is the Boltzmann constant. Our ambition was to relate calculations of {uexi,k}k=L,P at an atomistic scale to measurable partition coefficients obtained for bulky solutes with different stiffness and shape, such as hindered phenolic antioxidants, n-alkanes and n-alcohols. For large solutes in dense and cohesive phases (P or L), promising computation techniques involve free energy perturbation and non-equilibrium methods, thermodynamic integration, and extended ensembles (Gibbs or osmotic ensembles). Because the free energy landscape of the coupled i+k system contains several minima and highly heterogeneous barriers, a low convergence is generally achieved. To overcome such complications, we calculated {uexi,,k}k=L,P at atomistic scale in the framework of the Flory-Huggins approximation. The main advantage is that the mixing energy for a wide range of conformers was derived from pairwise interactions and a continuous approximation of the packing of molecules without representing explicitly large molecular systems. The translational entropy in L was inferred from a mesoscopic representation of the liquid medium matching the radial distributions calculated by isothermal and isobaric molecular dynamics simulations. The corresponding predictions were satisfactory compared with 38 experimen- * Please send correspondence to olivier.vitrac@agroparistech.fr.Brought to you by | University of North Dakota Authenticated Download Date | 5/31/15 5:26 AM tal K i , L/P values between polyethylenes, polystyrene and different alcohols (isopropanol, ethanol).

In the present review, natural and non-toxic particles made of micro/nanocellulose were specifically targeted as stabilizers of emulsions located at dispersed and continuous phases interfaces (called Pickering Emulsions, PEs). PEs are biphasic systems stabilized by solid particles with a recent interest in food and cosmetic domains. PEs have been more and more studied in the last ten years due to their advantages compared to conventional emulsions with surfactants. PEs have already been stabilized with various types of particles and particularly cellulose. Even if some studies showed that PEs were more stable when cellulose was chemically modified, numerous other recent studies showed that unmodified micro/nanocellulose is also promising biomaterial to stabilize PEs. Micro/nanocelluloses can be extracted by various green processes from numerous agricultural wastes and co-products, as banana peels, corncob, ginkgo seed shells, lime residues, mangosteen rind, oil palm empty fruit bunches, pistachio shells, as well as wheat straw. Main green processes used to treat cellulose are grinding, high pressure homogenization, microfluidization, enzymatic hydrolysis, subcritical water, extrusion, electron beam irradiation, cryocrushing, microwaves or sonication. PEs formulated with cellulose clearly participate to a global sustainable development but, additional studies will be necessary to better understand PEs stability and improve properties.