Glycated bovine serum albumin for use in feeding trials with animal models - In vitro methodology and characterization of a glycated substrate for modifying feed pellets.

This study investigated different methods to produce Nε-carboxymethyl-lysine (CML)-enriched bovine serum albumin (BSA) as alternatives to the classical approach using glyoxylic acid (GA) and sodium cyanoborohydride (NaBH3CN) which results in toxic hydrogen cyanide (HCN). The reaction of GA (6 mmol/L) and NaBH3CN (21 mmol/L) to produce CML remained the most effective with CML yields of 24-35%, followed by 13-24% using 300 mmol/L glyoxal (GO). GA promoted specific modification of lysine to CML, and fewer structural modifications of the BSA molecule compared with GO, as evidenced by fluorescence and proteomic analyses. GO promoted greater arginine modification compared with GA (76 vs 23%). Despite structural changes to BSA with GO, murine fecal clearance of CML was similar to literature values. Hence, BSA glycation with 300 mmol/L glyoxal is a suitable alternative to GA and NaBH3CN for generating CML-enriched protein free of HCN, but a CML-only fortification model remains to be described.

Semi-industrial production of a minimally processed infant formula powder using membrane filtration.

Infant formula (IF) is submitted to several heat treatments during production, which can lead to denaturation or aggregation of proteins and promote Maillard reaction. The objective of this study was to investigate innovative minimal processing routes for the production of first-age IF powder, thus ensuring microbial safety with minimal level of protein denaturation. Three nutritionally complete IF powders were produced at a semi-industrial scale based on ingredients obtained by fresh bovine milk microfiltration (0.8 and 0.1-µm pore size membranes). Low-temperature vacuum evaporation (50°C) and spray-drying (inlet and outlet temperatures of 160 and 70°C, respectively) were conducted to produce the T- formula with no additional heat treatment. The T+ formula was produced with a moderate heat treatment (75°C for 2 min) applied before spray-drying, whereas the T+++ formula received successive heat treatments (72°C for 30 s on the milk; 90°C for 2-3 s before evaporation; 85°C for 2 min before spray-drying), thus mimicking commercial powdered IF. Protein denaturation and Maillard reaction products were followed throughout the production steps and the physicochemical properties of the powders were characterized. The 3 IF powders presented satisfactory physical properties in terms of aw, free fat content, glass transition temperature, and solubility index, as well as satisfactory bacteriological quality with a total flora <103 cfu/g and an absence of pathogens when a high level of bacteriological quality of the ingredients was ensured. Protein denaturation occurred mostly during the heat treatments of T+ and T+++ and was limited during the spray-drying process. The IF powder produced without heat treatment (T-) presented a protein denaturation extent (6 ± 4%) significantly lower than that in T+++ (58 ± 0%), but not significantly different from that in T+ (10 ± 4%). Although T- tended to contain less Maillard reaction products than T+ and T+++, the Maillard reaction products did not significantly discriminate the infant formulas in the frame of this work. The present study demonstrated the feasibility of producing at a semi-industrial scale an infant formula being bacteriologically safe and containing a high content of native proteins. Application of a moderate heat treatment before spray-drying could further guarantee the microbiological quality of the IF powders while maintaining a low protein denaturation extent. This study opens up new avenues for the production of minimally processed IF powders.

Trace elements in e-liquids - Development and validation of an ICP-MS method for the analysis of electronic cigarette refills.

Electronic cigarette use has rapidly increased in recent years. In assessing their safety, and in view of coming regulations, trace elements (TE) are among the potentially toxic compounds required to be evaluated in electronic cigarette refill fluids ("e-liquids"). An analytical method using inductively coupled plasma with mass spectrometric detection (ICP-MS) was developed and rigorously validated in order to determine concentrations of 15 TE in 54 e-liquids from a French brand. Despite a significant matrix effect from the main e-liquid constituents, and difficulties related to the current lack of reference materials, our method demonstrated satisfactory linearity, precision and robustness, and permitted the quantification of low concentrations of these 15 elements: lower limits of quantification (LLQ) obtained were ≤4 ppb for all elements except for Ni, Cu and Zn (16 ppb, 20 ppb and 200 ppb, respectively). All TE concentrations in all tested samples were <510 ppb, mostly near or below the LLQs. This method is transposable and is timely for laboratories seeking to meet a prospective demand in light of current or future regulations.

PAHs associated with the leaves of three deciduous tree species. II: uptake during a growing season.

Leaves from three species of deciduous tree (oak, ash and hazel) were sampled at intervals through a growing season in a mature, mixed-deciduous woodland. Polycyclic aromatic hydrocarbon (PAH) concentrations remained within a small range for all species between May and September, deviating significantly only when increases in atmospheric concentrations of PAHs (notably from the 'Bonfire night' festival in early autumn) have been shown. We concluded that the influence of air concentrations was more important than meteorological conditions (temperature, humidity and rainfall) in determining plant concentrations of PAHs over a growing season. Concentrations of 4-, 5- and 6-ring PAHs were positively correlated with time for all species, but there were significant differences in the PAH profile between species sampled from the canopy (oak and ash) compared with the understorey (hazel). Oak and ash had similar PAH profiles, while hazel leaves had proportionally greater concentrations of the heavier molecular weight (4-, 5- and 6-ring) PAHs, and the ratios of these compounds to 3-ring PAHs was positively correlated with time. This affirms earlier work conducted on the same species in the same woodland, where we concluded that the canopy was filtering particles and attendant PAHs from air passing over or through it, and that these particles were transferred to the understorey and the woodland floor.

Further developments in the use of semipermeable membrane devices (SPMDs) as passive air samplers for persistent organic pollutants: field application in a spatial survey of PCDD/Fs and PAHs.

Semipermeable membrane devices (SPMDs) were deployed at 19 sites in northwest England to test their efficacy as passive atmospheric samplers for polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs). SPMDs were found to be efficient samplers for vapor phase species in the atmosphere, with good reproducibility between samplers. Species which are partially or completely particle associated under ambient U.K. conditions were also sampled by the SPMDs but with poorer reproducibility. It is suggested that SPMDs could be used to indicate "hotspots" of particulate associated species, however. Differences in absolute and relative concentrations of all PCDD/Fs and PAHs sequestered bythe SPMDs were observed between sites. High amounts were sequestered in SPMDs at sites where previous active monitoring has indicated relatively high atmospheric concentrations, confirming the potential of SPMDs as a tool for semiquantitative spatial monitoring of atmospheric species. SPMDs also respond to differences in the mixture of compounds present in the atmosphere, thereby aiding source apportionment studies.

Dynamics of PAH deposition, cycling and storage in a mixed-deciduous (Quercus-Fraxinus) woodland ecosystem.

Estimates of standing biomass and fluxes of biomass in a mixed-deciduous woodland were derived, and used with results for concentrations of seven polycyclic aromatic hydrocarbons (PAHs) in different compartments of the woodland system to quantitatively assess some of the key fluxes and burdens of PAHs in this complex system. We quantified PAH burdens in air, in leaves of three deciduous tree species, in leaf litter and in soil, and uptake of PAHs by the tree leaves; PAH fluxes in litterfall, and deposition to the litter layer on the woodland floor during winter were calculated from these data. Air burdens exhibited marked seasonal variations for all compounds, with lowest values in summer when combustion-related emissions were low. Leaves did not accumulate large burdens of PAHs while on the trees and consequently, litterfall-associated fluxes of PAHs were small, representing only a fraction of the burdens in the litter layer to which they were deposited. Higher PAH burdens in air in winter, combined with the organic-matter-rich nature of the litter layer, are thought to be responsible for fluxes of PAHs to the litter layer in winter being 20-170 times the peak litterfall fluxes. The soil compartment was calculated to contain 25 years' worth of deposition of benzo[ghi]perylene, the most recalcitrant PAH in this study. Storage quotients for fluoranthene, pyrene, benzo[k]fluoranthene and benzo[a]pyrene burdens in soil represented 7-10 years' worth of deposition, while fluorene and phenanthrene storage in soil approached unity with inputs (1 and 3 years' worth of deposition, respectively). The relative importance of storage and loss processes was therefore closely related to the physico-chemical properties of the PAH, and is discussed in relation to the cycling of carbon in the woodland.

Further developments in the use of semipermeable membrane devices as passive air samplers: application to PCBs.

There are several incentives for developing passive air sampling techniques for persistent organic pollutants (POPs). This paper reports on studies to further calibrate and optimize semipermeable membrane devices (SPMDs) for use as "integrated" air samplers of gas-phase POPs. These samplers are deployed over weeks/months/years. Polychlorinated biphenyls (PCBs) were used as the test compounds in this study, with three specific objectives: (i) to determine whether ambient wind speed limits the rate of uptake during typical deployment conditions; (ii) to monitor uptake and SPMD-air equilibrium for a range of compounds; and (iii) to assess the application of performance reference compounds (PRCs) in air sampling, to "correct" for site-specific differences in uptake rates. When deployed in Stevensons screens under ambient conditions, wind speed did not significantly affect uptake rates. Rather, differences in summer/winter uptake rates reported previously, using the same deployment devices as here, are due to temperature affecting compound permeability through the membrane. Results from the use of PRCs indicate that SPMDs should be spiked prior to exposure with a range of compounds that are not present in the atmosphere, so that uptake rates can be estimated from depuration rates during a particular deployment. Short-term deployments (e.g. days; few weeks) would need to use compound(s) with a low octanol:air partition coefficient (K(OA)) (e.g. 13C12 labeled PCB-28); long-term deployments (of many months to years) would need to use intermediate K(OA) compounds (e.g. 13C12 PCB-101; 13C12 PCB-153).

PAHs associated with the leaves of three deciduous tree species. I--Concentrations and profiles.

Results for the concentrations of total polycyclic aromatic hydrocarbons (Sigma PAH) and the PAH profile in leaves from three deciduous tree species from the same woodland are presented, and discussed with reference to environmental and leaf-related variables. There were significant differences between oak, ash and hazel leaves in their Sigma PAH concentrations (sum of 23 PAHs), and in the relative contribution of individual PAHs to the sum. Leaves exhibiting pubescence (hairiness) were found to have significantly higher Sigma PAH concentrations than hairless leaves, regardless of their position in the vegetation strata of the wood. Hazel leaves from the understorey had a PAH profile consisting of a greater proportion of the 4-, 5- and 6-ring PAHs than oak or ash from the canopy. This was concluded to be the result of the filtering effect of the main canopy on the air passing over and through it, with subsequent transfer of particles and attendant PAHs to the understorey below. The proportion of Sigma PAH contributed by the 6-ring PAH in hazel leaves was negatively correlated with distance from the southern edge of the canopy. It is proposed that the predominantly windward edges of the woodland, where atmospheric turbulence is likely to be greatest, favoured the deposition of particle-bound PAHs to leaves.