Evaluation of environmental contamination in beeswax products.

Beeswaxes are used as a coating agent or as a wrapping material for food products making them potentially ingested by consumers. There is no regulation yet in Europe giving maximum levels of contaminants in this type of product. Nevertheless, being a natural product, they are exposed to environmental pollution, thus it appears necessary to establish their contamination rate in order to evaluate potential human exposure. In this study, a method of extraction of different environmental contaminants including pesticides, phthalates, PAHs and phenols was developed. Based on a hot Soxhlet extraction, followed by cleaning steps, the method was validated for the quantitation of the cited contaminants by LC-MS/MS and GC-(MS)/MS. Three different types of waxes were analyzed including typical white waxes (Cera Alba) and yellow waxes (Cera Flava). It was shown that all waxes had the presence of at least one contaminant and that phthalates, in particular DEHP, was present in all beeswax samples. Insecticides were found in majority among all the classes of pesticides screened. The yellow waxes were found to be contaminated with the highest rates of PAHs (60%), pesticides (75%) and phenols (40%). The detection frequency of PAHs, in contrast to phthalates, was the lowest for all the types of waxes combined.

Impact of the protein composition on the structure and viscoelasticity of polymer-like gluten gels.

We investigate the structure of gluten polymer-like gels in a binary mixture of water/ethanol, 50/50 v/v, a good solvent for gluten proteins. Gluten comprises two main families of proteins, monomeric gliadins and polymer glutenins. In the semi-dilute regime, scattering experiments highlight two classes of behavior, akin to standard polymer solution and polymer gel, depending on the protein composition. We demonstrate that these two classes are encoded in the structural features of the proteins in very dilute solution, and are correlated with the presence of proteins assemblies of typical size tens of nanometers. The assemblies only exist when the protein mixture is sufficiently enriched in glutenins. They are found directly associated to the presence in the gel of domains enriched in non-exchangeable H-bonds and of size comparable to that of the protein assemblies. The domains are probed in neutron scattering experiments thanks to their unique contrast. We show that the sample visco-elasticity is also directly correlated to the quantity of domains enriched in H-bonds, showing the key role of H-bonds in ruling the visco-elasticity of polymer gluten gels.

Phase separation dynamics of gluten protein mixtures.

We investigate by time-resolved synchrotron ultra-small X-ray scattering the dynamics of liquid-liquid phase-separation (LLPS) of gluten protein suspensions following a temperature quench. Samples at a fixed concentration (237 mg ml-1) but with different protein compositions are investigated. In our experimental conditions, we show that fluid viscoelastic samples depleted in polymeric glutenin phase-separate following a spinodal decomposition process. We quantitatively probe the late stage coarsening that results from a competition between thermodynamics that speeds up the coarsening rate as the quench depth increases and transport that slows down the rate. For even deeper quenches, the even higher viscoelasticity of the continuous phase leads to a "quasi" arrested phase separation. Anomalous phase-separation dynamics is by contrast measured for a gel sample rich in glutenin, due to elastic constraints. This work illustrates the role of viscoelasticity in the dynamics of LLPS in protein dispersions.

Determination of polycyclic aromatic hydrocarbons in smoked and non-smoked black teas and tea infusions.

This study describes the occurrence of polycyclic aromatic hydrocarbons (PAHs) in smoked tea and tea infusions, via the monitoring of benzo(a)anthracene, chrysene, benzo(b)fluoranthene and benzo(a)pyrene (PAH4) that have been chosen as indicators for the occurrence of PAHs in food by the European Food Safety Agency. The concentrations ranged from 1.2 µg/kg for benzo(b)fluoranthene to 125.0 µg/kg for benzo(a)anthracene in smoked tea leaves, and from 0.6 µg/L for benzo(a)anthracene to 1.2 µg/L for benzo(b)fluoranthene in smoked tea infusions. Benzo(a)pyrene was never detected in infusions. The concentrations in non-smoked tea leaves ranged from 0.6 µg/kg for benzo(a)anthracene to 10.8 µg/kg for benzo(b)fluoranthene. It was shown that the concentrations of benzo(a)anthracene and chrysene were higher in smoked tea than in non-smoked tea while no difference was observed for benzo(b)fluoranthene and benzo(a)pyrene. The concentrations of PAHs in tea infusions are low compared to other foodstuffs, but the migration rates from leaves into water are high (82-123%).