Interaction of food packaging material and selected food components under high pressure

Abstract

Interactions between ethanolic solutions of p-cymene and acetophenone and different polymer packaging materials. were studied at 500 MPa and 25° C. p-Cymene solution, filled into low-density polyethylene bags, lost 30% of its aroma concentration after 24 h at 500 MPa compared to a 60% loss at atmospheric pressure. The decrease was strongest within the first 15 min. Using LDPE/HDPE/LDPE bags, losses were 20% and 30%, resp. Applying the “bag in the bag” method, p-cymene concentrations measured inside and outside the inner bag has shown sorption by the pressurized film to be one third of that by the non-pressurized. In PET/AI/LDPE bags impermeable to p-cymene, sorption was confined to the inner LDPE layer and caused higher loss in the non-pressurized sample. Acetophenone has not been found to interact with the polymer during pressure treatment, while at atmospheric pressure sorption loss in aroma concentration was nearly 70% after 60 h.     

Multiscale analysis and simulation of a reaction–diffusion problem with transmission conditions

This paper considers a transmission problem for partial differential equations obtained in the recent paper [M. Neuss-Radu, W. Jäger, Effective transmission conditions for reaction-diffusion processes in domains separated by an interface, SIAM J. Math. Anal. 39 (2007) 687–720] as the effective system modeling a reaction–diffusion process in two domains separated by a membrane. For the analysis of this problem an appropriate function space, which includes the coupling conditions for the concentrations on the interface, is introduced. The transmission conditions for the flux are included in the variational formulation with respect to this function space.The solution of the transmission problem is approximated by using the Galerkin method. Numerically the problem is reduced to a system of ordinary differential equations, where the coupling of the micro- and macro-variables leads to a special structure, distinguishing the variables relevant for the transmission. Results of numerical simulations are illustrating the effect of the microscopic process in the membrane on the macroscopic reaction–diffusion process in the bulk domains.     

Solvent-induced crystallization. I. Crystallization kinetics

The kinetics of crystallization of quenched poly(ethylene terephthalate) (PET) films during the imbibition of methylene chloride (MeCl₂) vapor is studied by density measurements. The effects of film thickness (0.0025–0.086 cm) and temperature (0–38°C) were examined. The data suggest that MeCl₂ transport controls the crystallization in thick films and at elevated temperatures, but that spherulite growth controls in thin films and at reduced temperatures. The application of a mathematical model developed previously supports this mechanistic interpretation of the data.     

Simulation of elastic–plastic deformation and fracture of materials at micro-, meso- and macrolevels

Physical Mesomechanics of materials is a new branch of mechanics that focuses attention on a mesovolume of loaded material. It is a macro particle in classical continuum mechanics and its behavior under load is equivalent to the bulk. The structural elements for a particular application requires specific models while the computational techniques have to be developed.These research groups have been studying heterogeneous materials behavior at the mesolevel under different types of loading. Hierarchical models are developed to study deformation and fracture of solids at the micro- meso- and macrolevels. Taken into account are the influence of micro- and mesostructure of loaded material in relation to its macro behavior.This work focuses on unifying the method of approach to be supported by tests and calculations. In particular, deformation and fracture mechanisms at the micro-, meso- and macrolevels are examined for metals and composites.     

[CrBr2(NH3)4][CrBr4(NH3)2], a new chromium(III) complex

Green single crystals of trans‐tetraamminedibromidochromium(III) trans‐diamminetetrabromidochromate(III), [CrBr₂(NH₃)₄][CrBr₄(NH₃)₂], are found to contain two symmetry‐independent sixfold coordinated Cr^III cations on centres of inversion. The structure is composed of octahedral trans‐[CrBr₂(NH₃)₄]⁺ cations and octahedral trans‐[CrBr₄(NH₃)₂]⁻ anions, and adopts a distorted CsCl‐type lattice. The cations and anions are linked by N—H...Br interactions. This is the first example in which both ions are mixed ammine–bromide Cr^III complexes.     

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