Accurate determination of 2,4,6-trichloroanisole in wines at low parts per trillion by solid-phase microextraction followed by GC-ECD

A headspace solid-phase microextraction (HS-SPME) procedure at 30 degrees C with a 100 microm PDMS fiber of a saturated NaCl solution stirred at 1100 rpm combined to GC-ECD for the 2,4,6-trichloroanisol (TCA) determination in wines has been developed. Due to the matrix complexity and ethanol absorption into the fiber, the internal standard selection was crucial to obtain unbiased results. Thus, matrix effects were observed when analyzing different types of Spanish wines (white, early, and vintage red wines) spiked with TCA at low concentration levels (i.e., <40 ng L(-)(1)). In contrast, the use of 2,4,6-tribromoanisole (TBA) as internal standard overcame these matrix effects, whereas the use of 2,4,6-trichlorophenyl ethyl ether led to inconsistent results. The developed HS-SPME-GC-ECD methodology reaches a limit of quantitation for TCA in wine within 2.9-18 ng L(-)(1), with a relative standard deviation of 2.5-13.4%, depending on the TCA concentration level and wine characteristics. This analytical method is comparable to the existing methodologies based on HS-SPME followed by GC-MS in terms of accuracy, precision, length of determination, and length of quantification; however, analysis cost is reduced.     

Monitoring of subaqueous depots with active barrier systems for contaminated dredged material using dialysis samplers and DGT probes

Background, Aims and Scope  Disposal of dredged material in subaqueous depots is increasingly considered an economic and ecologically sound option in managing contaminated dredged material. The concept of subaqueous disposals capped with active barrier systems has been developed to minimize this risk of contaminant release. As such a depot represents a permanent installation within a sensitive ecosystem, it requires a thorough monitoring concept. It is the goal of this work to develop such a concept regarding general considerations and results of laboratory and field investigations. Methods  In addition to the state-of-the-art techniques developed for other under-water constructions, this monitoring concept is developed with particular respect to the chemical isolation of the dredged material from the overlying water body. It comprises the use of seepage meters, dialysis samplers, and DGT gel probes for determining the migration of selected target solutes. The capability of the dialysis samplers is demonstrated by comparing field results with model calculations. The appropriateness of DGT probes to assess the impact of humic substances on trace metal speciation and on copper toxicity is demonstrated with the aid of laboratory experiments. Results and Discussion  The experimental results show that, by using dialysis samplers, the temporal changes in concentration-depth-profiles of heavy metals in the pore solution can be monitored. Additionally, the application of DGT probes facilitates the in situ detection of labile species of a metal in the presence of dissolved humic substances, which serves to reflect its toxicity. Conclusions. Three subsequent monitoring phases are distinguished on the basis of both general considerations and the findings from field results: A hydraulic phase that is characterized by compaction and pore water expulsion, a geochemical phase in which the demobilization of pollutants can occur due to substantial changes in the physico-chemical conditions (pH, EH), and a steady-state-phase where pore water flow and geochemical conditions are approaching their minimum. Recommendations and Outlook  The monitoring concept suggested here provides a versatile tool to assess the chemical isolation of subaqueous sediment depots and other contaminated sediment sites. This is of great importance as subaqueous disposal is increasingly considered a future management strategy as space for upland disposal is limited and treatment, in general, proves to be too costly.     

Robust two-stage approach to repeated measurements analysis of chronic ozone exposure in rats

A robust two-stage approach is used to reanalyze the repeated measurements from an experiment of airway responsiveness in rats randomized to long-term exposure at four ozone doses. The concentration-response data generated for each rat may be represented as a hierarchical nonlinear model encompasing the sources of variation within and between individual profile for each rat, the conditional modeling approach can assess the adequacy of an assumed mean model, a fundamental advantage not intrinsic to marginal techniques. The two-stage population inference is based on the estimated individual parameters, thus maintaining an intuitive appeal to the toxicologists who traditionally have fitted a separate curve for each animal and then applied ANOVA to the summary statistics. However, we formally adjust the standard errors for the extra variability due to the initial estimation of the individual parameters and also allow for their within-rat correlation. The robust two-stage method appropriately down weights the a berrant responses arising sporadically within individualsand, more importantly, the rats which may be outlying relative to the usual population variation. The true effect of chronic ozone exposure, including a significant gender interaction, may be masked by a few rats which exert undue influence on the population estimates in a nonrobust analysis.     

Analysis of photoperiod sensitivity within a collection of tropical maize populations

We analyzed the variability of a large maize (Zea mays L.) collection of152 tropical populations for photoperiod sensitivity and grain productivityunder long-day conditions to investigate their potential adaptation to temperateconditions. A multilocal experimental design was used: one location withshort-day conditions (Guadeloupe), one location with medium-day conditions (latesowing in the south of France) and two locations with long-day conditions (earlysowing in both the North and South of France). The photoperiod sensitivity wasestimated by the slope of the regression of thermal time from sowing to 50%anthesis on photoperiod. We found highly significant effects of latitude andaltitude of the collecting site of the population on photoperiod sensitivity anda significant but small interaction between these two factors. Populationsoriginated from low altitudes and low latitudes are highly sensitive tophotoperiod, whereas highland populations never display a high photoperiodsensitivity, whatever the latitude of origin. Grain productivity under long-dayconditions was not highly correlated with photoperiod sensitivity. Andeanpopulations were little sensitive to photoperiod and exhibited poor grainproduction under long-day conditions. In contrast, some populations from theCaribbean such as populations from Cuban Flint and Early Caribbean racesexhibited a good grain production although sensitive to photoperiod. The goodadaptation of some Caribbean material to temperate conditions is consistent withthe hypothesis of the successful introduction of Caribbean germplasm in southernregions of the Old World.     

Thermal degradation products formed from carotenoids during a heat-induced degradation process of paprika oleoresins (Capsicum annuum L.)

The high-temperature treatment of paprika oleoresins (Capsicum annuum L.) modified the carotenoid profile, yielding several degradation products, which were analyzed by HPLC-APCI-MS. From the initial MS data, compounds were grouped in two sets. Set 1 grouped compounds with m/z 495, and set 2 included compounds with m/z 479, in both cases for the protonated molecular mass. Two compounds of the first set were tentatively identified as 9,10,11,12,13,14,19,20-octanor-capsorubin (compound II) and 9,10,11,12,13,14,19,20-octanor-5,6-epoxide-capsanthin (compound IV), after isolation by semipreparative HPLC and analysis by EI-MS. Compounds VII, VIII, and IX from set 2 were assigned as 9,10,11,12,13,14,19,20-octanor-capsanthin and isomers, respectively. As these compounds were the major products formed in the thermal process, it was possible to apply derivatization techniques (hydrogenation and silylation) to analyze them by EI-MS, before and after chemical derivatization. Taking into account structures of the degradation products, the cyclization of polyolefins could be considered as the general reaction pathway in thermally induced reactions, yielding in the present study xylene as byproduct and the corresponding nor-carotenoids.     

Volatile components and key odorants of fennel (Foeniculum vulgare Mill.) and thyme (Thymus vulgaris L.) oil extracts obtained by simultaneous distillation-extraction and supercritical fluid extraction

Volatile oil extracts of fennel seeds (Foeniculum vulgare Mill.) and thyme leaves (Thymus vulgaris L.) were obtained by simultaneous distillation-extraction (SDE) and supercritical fluid extraction (SFE) and analyzed by gas chromatography-mass spectrometry (GC-MS). In general, fennel oil extracted by SDE and SFE showed similar compositions, with trans-anethole, estragole, and fenchone as the main components. In contrast, thymol and p-cymene, the most abundant compounds in thyme leaves, showed big differences, with generally higher amounts of monoterpenes obtained by SDE. However, in this case, the differences between the extracts were higher. Key odorants of fennel seeds determined by gas chromatography-olfactometry (GC-O) showed similar patterns when applying SDE and SFE. trans-Anethole (anise, licorice), estragole (anise, licorice, sweet), fenchone (mint, camphor, warm), and 1-octen-3-ol (mushroom) were the most intense odor compounds detected in fennel extracts. Thymol and carvacrol, with oregano, thyme, and spicy notes, were identified as key compounds contributing to the aroma of thyme leaves.     

Effect of accelerated autolysis of yeast on the composition and foaming properties of sparkling wines elaborated by a champenoise method

Five mutants (obtained by UV mutagenesis) and the parent strain were selected to produce sparkling wines following the traditional or champenoise method. The wines were aged with the yeast for 9 months, with samples being taken each month for analytical and sensory determinations. The wines elaborated with mutant strain IFI473I demonstrated an accelerated release of protein, amino acids, and polysaccharides. An analysis of the secreted polysaccharides revealed that mannose was the major sugar present. The effects of the products released by yeasts on the foaming properties of the wines were determined by both sensory and instrumental analysis. In all cases, the wines elaborated with mutant strain IFI473I showed improved foaming properties as compared to wines fermented without this strain. Similar results were obtained at a decreased aging time of 6 months, thereby confirming the capacity of IFI473I strain to carry out an accelerated autolysis. These results demonstrate that mutant strain IFI473I can significantly reduce production times of high-quality sparkling wines.     

Phospholipid interactions protect the milk allergen alpha-lactalbumin from proteolysis during in vitro digestion

Interactions with food components may alter the resistance of food proteins to digestion, a property thought to play an important role in determining allergenic properties. The kinetics of breakdown of the bovine milk allergen alpha-lactalbumin during in vitro gastrointestinal digestion was found to be altered by interactions with physiologically relevant levels of phosphatidylcholine (PC), a surfactant that is abundant both in milk and is actively secreted by the stomach. Breakdown during gastric digestion was slowed in the presence of PC and accompanied by small alterations in the profile of resulting peptides, with little effect being observed during subsequent duodenal digestion. alpha-Lactalbumin was found to unfold at gastric (acid) pH, giving a CD spectrum similar to that obtained for the partially folded state it is known to adopt at pH values below its isoelectric point. Fluorescence polarization studies performed at low pH indicated that this partially unfolded form of the protein was able to penetrate into the PC vesicles. These interactions are probably responsible for the slowing of gastric digestion by reducing the accessibility of the protein to pepsin. These findings show that interactions with other food components, such as lipids, may alter the rate of breakdown of food proteins in the gastrointestinal tract. It underlines the importance of the food matrix in affecting patterns of food allergen digestion and hence presentation to the immune system and that in vitro digestion systems used for assessing digestibility of allergens must take account of surfactants.