Thiol precursors in Catarratto Bianco Comune and Grillo grapes and effect of clarification conditions on the release of varietal thiols in wine

Background and Aims

Varietal thiols characterise the typical aroma of several white wines, such as Sauvignon Blanc. Their presence and sensory perception were suggested in two Sicilian grape cultivars, Catarratto Bianco Comune (CBC) and Grillo, though it has not been analytically proven.

Methods and Results

Varietal thiol precursors and free varietal thiols were assessed in CBC and Grillo grapes, musts and wines by ultra‐performance liquid chromatography/electrospray ionisation high‐resolution MS. The isobaric compounds including S‐3‐(hexanal)‐glutathione and S‐3‐(4‐mercapto‐4‐methylpentan‐2‐one)‐glutathione (GSH‐4MMP) were distinguished by comparing their accurate masses and high‐resolution‐MS/MS spectra with those of their synthetic standards. S‐3‐(Hexanal)‐glutathione, S‐3‐(hexan‐1‐ol)‐glutathione and S‐3‐(hexan‐1‐ol)‐cysteine were found in grape, must and wine, whereas GSH‐4MMP and its hydrolysed forms were not found. Their concentration decreased during winemaking, mostly after grape pressing. We compared the effect of clarification conditions based on the exposure of must to either air or CO₂ on the concentration of thiol precursors and free thiols in wine; however, negligible differences were observed. The concentration of free thiols in the wines was found to be in the range 400–1100 ng/L and they were unaffected by the two clarification conditions tested.

Conclusions

The isobaric S‐3‐(hexanal)‐glutathione and GSH‐4MMP were clearly distinguished for the first time by ultra‐performance liquid chromatography/high‐resolution MS through their retention times and MS spectra. These varietal thiols were revealed in CBC and Grillo wines for the first time. The air‐free and air‐exposed clarification treatments had little effect on the concentration of the varietal thiols.

Significance of the Study

This study highlights the major impact of the varietal thiols (mainly 3‐mercapto‐hexan‐1‐ol and its acetate form) on the sensory properties of CBC and Grillo wines.     

Electrochemistry on microcircuits. II: Copper dendrites in oxalic acid

A new chip, which consists in an array of microelectrodes of various size and geometry, was realized by means of an industrial CMOS process. The microelectrodes were arranged as couples between which copper dendrites were able to grow in oxalic acid media up to short circuit the two electrodes. The current transient generated by the dendrite growth observed when a potential step was applied between the two microelectrodes was used to characterize the dendrite kinetics. In particular, the short circuit was detected when the current increased abruptly after some time called short circuit time. The influence of the oxalic acid concentration and of the geometry for the square-bar and lozenge-bar patterns on the short circuit time was investigated. At the end, some possibilities of partial inhibition of the dendritic growth were tested: addition of a supporting electrolyte, modification of the pH of the solution, addition of an inhibitor.     

Experimental study of the relationships between the electrochemical noise and the structure of the electrodeposits of metals

A new technique allows us to measure the electrochemical noise generated during the electrocrystallization of zinc and nickel. Relationships have been put forward: (i) between the noise power and the preferred orientation of nickel electrodeposits, (ii) between the noise power and the morphology of zinc electrodeposits. Possible interpretations of these results are discussed.     

A Review of Online Advertising Effects on the User Experience

This article reviews empirical research conducted in the last decade on the subject of how online display advertising affects the usability and quality of user experience of websites. In particular, from an in-depth analysis of research questions, methods, and findings of the reviewed studies, the following is discussed: (a) which conceptual and theoretical background knowledge, based on psychological explanations of user cognition, affection and behavior, can best support the design and investigation of online advertising, and (b) which specific adverts features and properties are key to understand and favor certain types of effects on users. By capitalizing on this benchmark knowledge on benefits of adverts and their hidden costs, web researchers and practitioners are encouraged to approach online advertising from a deeper and more comprehensive perspective, which is centered on qualities of web interaction that go beyond traditional usability factors. It is speculated that many of the theories and models developed for advertising effectiveness, and variables used to measure it, could and should be applied also when assessing the quality of the user experience when using websites in general, regardless of whether they contain adverts.     

Nailfold capillary microscopy in patients with antiphospholipid syndrome

In this paper we tried to define the capillaroscopic pattern of anti phospholipid syndrome able to differentiate between the primary (PAPS) and the systemic lupus erythematosus-associated form (SLE-APS) and to be a predictive marker of thrombotic manifestations. Eight PAPS and five SLE-APS patients were studied. In each patient the evaluation was based on anti cardiolipin antibody levels, nailfold capillaroscopy, retinal fluorangiography and transcranial doppler sonography. Statistical analysis has been performed using chi 2 analysis. Morphological alterations of capillary loops, venular visibility and sludging of blood were often observed in both groups. While we found in higher prevalence a variability of capillary loop length in PAPS patients, the SLE-APL group significantly differed for the presence of microhaemorrhages (p < 0.001). When we evaluated the clinical history, a marked microcirculatory damage was related with the occurrence of thrombotic manifestations in the PAPS patients. Anti cardiolipin antibody levels, retinal fluorangiography and transcranial doppler sonography did not correlate with clinical history in either group. In conclusion, nailfold capillaroscopy can be usefully employed in the differentiation between primary and SLE-associated anti phospholipid syndrome, and it can help to identify the patients at higher risk of thrombotic disease.     

Ultrasonography in the detection of aneuploidy in the first trimester

Ultrasonography has been used increasingly in the first trimester to identify fetal anomalies as early as possible in gestation. First trimester sonographic screening may detect a greater proportion of aneuploid fetuses than sonography performed later in pregnancy, and it may allow determination of potential markers for prediction of chromosomal anomalies.     

Electrochemical and electrogravimetric behaviors of conducting polymer. Theoretical aspects and application to co-polymer films based on juglone

Redox mechanisms of conducting polymers are not yet fully understood. Attractive analytical tools and pertinent models are necessary to achieve this goal. In this paper, numerical simulations based on a theory dealing with ions transfer through electroactive film/electrolyte interface was developed to predict the behavior of a conducting polymer called poly(JUG-co-JUGA). The main advantage of this approach is that it can be applied for any polymer assuming a mixed conducting material and a thin enough film neglecting the transport effect. It is the first time where the same model allows both classical cyclic electrogravimetry (current and mass over a potential scan) and ac-electrogravimetry (electrochemical impedance and mass/potential transfer functions) to be estimated theoretically. Moreover and to our knowledge the electrochemical behavior of poly(JUG-co-JUGA) was examined through these techniques for the first time. It is shown herein that the cation transfer is preponderant but the free solvent motion must be taken into account. This effect is not detected by classical electrochemical measurements but only by combining electrochemical characterization to gravimetric measurements.     

Direct determination of rare earth elements at the subpicogram per gram level in antarctic ice by ICP-SFMS using a desolvation system

A method, based on inductively coupled plasma sector field mass spectrometry coupled with a microflow nebulizer and a desolvation system, has been developed for the direct determination of rare earth elements (REE) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) down to the subpicogram per gram level (1 pg/g = 10(-12) g g(-1)) in approximately 1 mL of molten Antarctic ice. Contamination problems were carefully taken into account by adopting ultraclean procedures during the sample pretreatment phases. The use of a desolvation system for sample introduction during the analysis greatly reduced spectral interferences from oxide formation; the residual interfering contributions were calculated and subtracted whenever necessary. A matched calibration curve method was used for the quantification of the analytes. Instrumental detection limits ranged from 0.001 pg/g for Ho, Tm, and Lu to 0.03 pg/g for Gd. The precision, in terms of relative standard deviation on 10 replicates, ranged from 2% for La, Ce, Pr, and Lu, up to 10% for Er, Tm, and Yb. This methodology allowed the direct determination of REE in a 1-mL sample of ancient Antarctic ice with concentration ranges between 0.006 and 0.4 pg/g for Tm and 0.9-60 pg/g for Ce.     

Prediction of flow curves and forming limit curves of Mg alloy thin sheets using ANN-based models

Multivariable empirical models based on artificial neural networks were developed in order to predict the flow curves and forming limit curves of AZ31 magnesium alloy thin sheets, in warm forming conditions, vs. process parameters and fibre orientation. Experimental tensile and hemispherical punch tests were carried out in order to obtain the experimental data set, in terms of flow curves and forming limit curves, to be used to train the artificial neural networks. A preliminary study, based on the leave one-out-cross validation methodology, has proven the very good predictive capability of the ANN-based models in modelling both flow curves (flow stress level, curve shape and strain at the onset of necking) and forming limit curves (curve shape, major strain values and minor strain limit) under different process conditions and fibre orientations. Then, the generalisation capability of the neural models in capturing the effect of process parameters and fibre orientation on flow curves and formability has been proven by the excellent agreement, in terms of the high correlation coefficients, low relative errors and average absolute relative errors, between predicted and experimental results not investigated in the training set.