Optimisation of stir bar sorptive extraction for the analysis of volatile phenols in wines

An easy, fast and reliable analytical method is proposed for the determination of the concentration of volatile phenols (ethyl- and vinylphenols) in wines. The novel stir bar sorptive extraction (SBSE) technique is employed, following a simple and fast procedure that allows 15 samples to be extracted simultaneously using very small sample volume. Extracts are desorbed in a thermodesorption system (TDS) coupled on-line to a gas chromatograph-mass spectrometry system. The SBSE offers better recovery and linear regression coefficient (r2) for the four volatile phenols than solid-phase extraction (SPE). The mass spectrometric detection in selected ion monitoring mode contributes to the lower detection limit and good sensibility obtained with this method.     

Fatty Acid and Tocopherol Composition of Pomace and Seed Oil from Five Grape Varieties Southern Spain

Grape pomace and seeds are important winemaking by-products. Their oils are rich in bioactive compounds such as fatty acids and tocopherols. We have characterized oils from both by-products from five Spanish grape varieties (Palomino Fino, Pedro Ximénez, Muscat of Alexandria, Tempranillo and Tintilla de Rota). A high content of UFAs was found in all the analyzed samples. Grape pomace oils generally had the same oleic acid (PUFA_ω-6) content as seed oils, and lower PUFA contents; they also had a markedly higher linolenic acid (PUFA_ω-3) content, improving the PUFA_ω-6/PUFA_ω-3 ratio. All the oil studied show good indicators of nutritional quality: low values of the atherogenicity (0.112–0.157 for pomace, 0.097–0.112 for seed) and thrombogenicity indices (0.30–0.35 for pomace, 0.28–0.31 for seed) and high values of the relationship between hypo- and hypercholesterolemic fatty acids (6.93–9.45 for pomace, 9.11–10.54 for seed). Three tocopherols were determined: α-, γ- and δ-tocopherol. Pomace oils have higher relative contents of α- and δ-tocopherol, whereas seed oils have higher relative contents of γ-tocopherol. A significantly higher content of total tocopherols has been found in pomace oil; it is higher in the oils from red varieties of pomace (628.2 and 706.6 mg/kg by-product), and in the oils from pomace containing stems (1686.4 mg/kg by-product). All the oils obtained can be considered as a source of vitamin E, and their consumption is beneficial for health.     

Development and validation of UPLC for the determination of phenolic compounds and furanic derivatives in Brandy de Jerez

Brandy and other aged distillates are a rich source of polyphenols. For brandies, contact with wood during ageing makes an important contribution to their polyphenols content. This paper describes the use of a previously devised ultra performance LC (UPLC) method to study the polyphenols content of Brandy de Jerez. UPLC is a new technique in LC offering several potential advantages, especially the reduction of time. Analyses of brandy performed by HPLC were repeated by UPLC. A special UPLC analytical column (Acquity UPLC BEH C₁₈ column, 100×2.1 mm), with a particle size of 1.7 μm, forms part of this system. Using the UPLC system enabled the time needed for analysis to be reduced to one tenth of the time needed in the conventional HPLC system. In conclusion, the separation factor results of the UPLC were compared to those obtained using HPLC methods; this demonstrated that simple, high efficiency UPLC gradients are viable and advantageous substitutes for traditional analysis of polyphenols in brandy by HPLC. The method enabled 14 phenolic compounds to be identified and determined in 33 different commercial brandies, and this allowed them to be differentiated in function of quality.     

Validation of two analytical methods for the determination of ochratoxin A by reversed-phased high-performance liquid chromatography coupled to fluorescence detection in musts and sweet wines from Andalusia

Some Spanish sweet wines are made from raisins, grapes dried by direct exposure to the sun after picking. This drying process can encourage ochratoxin A (OTA) formation. OTA is a mycotoxin formed by several fungi. It has been linked to nephropathy in humans, and may have a long half-life in humans. The aim of this study is to develop and to apply two procedures for the analysis of OTA in grape musts (during the raisining process) and sweet wines, respectively. Reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to fluorescence detection (FLD) was employed in both analytical methods. In grape must, the method involves the direct injection of the sample in a HPLC-FLD system without any kind of prior clean-up procedure. The complexity of the sweet wine samples requires a solid-phase extraction (SPE) clean-up on a C18 column which enables the OTA to be isolated from the matrix. The methods used were statistically validated. The validation also included the comparison of the slopes of the curve obtained with standards and the regression curves obtained by the addition of a standard. Two different studies of standard additions were conducted. One method was validated without sample preparation and it was applied to must samples. The other method was validated with SPE extraction and it was applied to sweet wine samples. Recovery was always better than 89.69%. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) were established at 0.22 and 0.77 μg l⁻¹, respectively. In general, the analytical data obtained provided good results at the sub-μg l⁻¹ concentration level.     

Analytical and Chemometric Characterization of Fino and Amontillado Sherries during Aging in Criaderas y Solera System

Fino and Amontillado are Sherry wines, produced in Marco de Jerez area (southern Spain), and aged in Criaderas y Solera system. Fino Sherry wine follows a biological aging process, under a veil of flor yeasts, while Amontillado Sherry wine shares the same biological aging firstly, followed by oxidative aging, which gives them special features. Organic acids, esters, higher alcohols, phenolic compounds and total dry extract of Sherries evolve during aging due to evaporation processes, physical-chemical reactions, wood contributions and microbiological activity. During aging, Sherry wines improve their organoleptic profile, as could be proved in the tasting sessions. Hierarchical Cluster Analysis and Factor Analysis with factor extraction using Principal Components of Sherry wines studied were carried out and natural groupings of the wines according to the type of aging and their age were observed. A strong correlation between the parameters analyzed and the aging of each wine has been seen in the Multiple Linear Regression studies, establishing two different models, one for each type of Sherry wine, that, with only four of all the variables studied estimated the wine age with more than 99% of confidence. This constitutes a useful tool to control the age of these Sherry wines in the winery.     

Optimal structure of complex networks for minimizing traffic congestion

To design complex networks to minimize traffic congestion, it is necessary to understand how traffic flow depends on network structure. We study data packet flow on complex networks, where the packet delivery capacity of each node is not fixed. The optimal configuration of capacities to minimize traffic congestion is derived and the critical packet generating rate is determined, below which the network is at a free flow state but above which congestion occurs. Our analysis reveals a direct relation between network topology and traffic flow. Optimal network structure, free of traffic congestion, should have two features: uniform distribution of load over all nodes and small network diameter. This finding is confirmed by numerical simulations. Our analysis also makes it possible to theoretically compare the congestion conditions for different types of complex networks. In particular, we find that network with low critical generating rate is more susceptible to congestion. The comparison has been made on the following complex-network topologies: random, scale-free, and regular.     

Renormalization group fixed points in the local potential approximation ford≧3

In the Local Potential Approximation, renormalization group equations reduce to a semilinear parabolic partial differential equation. Felder [8] has derived this equation and has constructed a family of non-trivial fixed pointsu _2n ^* (n=2,3,4,...) which have the form ofn-well potentials and exist in the ranges of dimensions 2<d<2+2/n–1. In this paper we show that ifd4, then these non-trivial fixed points disappear, and if 3d<4 then we have only theu ₄ ^* fixed point.Research supported by CNPq, Brazil     

Schizocalyx cuspidatus (A. St.-Hil.) Kainul. & B. Bremer extract improves antioxidant defenses and accelerates the regression of hepatic fibrosis after exposure to carbon tetrachloride in rats

The aim of this study was to investigate the effect of leaves extract of Schizocalyx cuspidatus (A. St.-Hil.) Kainul. & B. Bremer on hepatic morphofunctional dysfunction induced by carbon tetrachloride (CCl₄). Liver lesions were induced via intraperitoneal administration of CCl₄ every 48 h for 12 days. Forty-nine rats were randomised into seven groups: G1: CCl₄; G2: CCl₄ (animals euthanised 24 h after last CCl₄ application); G3: CCl₄ + DMSO; G4: SCE 400 mg/kg; G5: DMSO (700 μl); G6: CCl₄ + SCE 200 mg/kg and G7: CCl₄ + SCE 400 mg/kg. SCE administration resulted in reduction in hydroperoxide levels, lipidic droplets and necrosis compared to G1, G2 and G3. There was an increase in the amount of collagen fibres in G1, G2 and G3 compared to the groups. These results show that the extract of SCE leaves has great potential for the recovery of liver damage after the application of CCl₄.     

Synthesis, solid state structure and polymerisation of a fully planar cyclopentadithiophene

The new fully planar cyclopentadithiophene, 4-n-dodecylidene-4H-cyclopenta(2,1-b;3,4-b')dithiophene, shows extensive pi-stacking in the solid state with short intermolecular distances (ca. 3.5 A) between adjacent molecules. Polymerisation of this monomer by two different protocols gave solution processable alkenyl-bridged cyclopentadithiophene polymers with extended pi-conjugation in the main chain.