V. Felipe Laurie

Analysis of selected carbonyl oxidation products in wine by liquid chromatography with diode array detection.

A high performance liquid chromatography (HPLC) method for the detection and quantitation of acetaldehyde, glyceraldehyde, pyruvic acid, 2-ketoglutaric acid, and formaldehyde in wine, based on the formation of the 2,4-dinitrophenylhydrazones, is presented. These carbonyl compounds often result from the chemical oxidation of major wine components, and are known to affect flavor and color stability. Their analysis in wine is complicated due to their instability and their tendency to react reversibly with bisulfite to form alpha-hydroxysulfonates. Published methods that break down the sulfonates for the quantitation of total carbonyls in wine involve alkaline hydrolysis of sulfite-bound carbonyls, but we show, for the first time, that this alkaline treatment step significantly increases the concentration of carbonyls during analysis. A solution based on oxygen exclusion is described. The technique offers good specificity, reproducibility (%RSD 0.45-10.6), and limits of detection (1.29-7.53microgL(-1)). The method was successfully used to monitor concentration changes of these compounds in both white and red wines.

Investigation of Ethyl Radical Quenching by Phenolics and Thiols in Model Wine

In the present study, the reaction between 1-hydroxyethyl radicals (1-HER) and various wine-related phenolics and thiols, including gallic acid, caffeic acid, ferulic acid, 3-mercaptohexan-1-ol (3MH), cysteine (Cys), and glutathione (GSH), was studied using competitive spin trapping with electron paramagnetic resonance (EPR) and mass spectrometry. Previous studies have reported several important reactions occurring between quinones and other wine components, but the fate of 1-HER within the context of wine oxidation is less understood. Furthermore, the ability of these compounds to prevent formation of acetaldehyde, a known nonenzymatic oxidation product of ethanol, was measured. The hydroxycinnamic acids and thiol compounds tested at 5 mM concentrations significantly inhibited spin adduct formation, indicating their reactivity toward 1-HER. In addition, we confirm that loss of 3MH under model wine conditions is due to quinone trapping as well as 1-HER-induced oxidation.

Tracing phenolic biosynthesis in Vitis vinifera via in situ C-13 labeling and liquid chromatography–diode-array detector–mass spectrometer/mass spectrometer detection

Phenolic compounds in Vitis vinifera contribute important flavor, functionality, and health qualities to both table and wine grapes. The plant phenolic metabolic pathway has been well characterized, however many important questions remain regarding the influence of environmental conditions on pathway regulation. As a diagnostic for this pathways regulation, we present a technique to incorporate a stable-isotopic tracer, L-phenyl-(13)C(6)-alanine (Phe(13)), into grape berries in situ and the accompanying high throughput analytical method based on LC-DAD-MS/MS to quantify and track the label into phenylalanine metabolites. Clusters of V. vinifera cv. Cabernet Sauvignon, either near the onset of ripening or 4 weeks later, were exposed to Phe(13) in the vineyard. Phe(13) was present in berries 9 days afterwards as well as labeled flavonols and anthocyanins, all of which possessed a molecular ion shift of 6 amu. However, nearly all the label was found in anthocyanins, indicating tight regulation of phenolic biosynthesis at this stage of maturity. This method provides a framework for examining the regulation of phenolic metabolism at different stages of maturity or under different environmental conditions. Additionally, this technique could serve as a tool to further probe the metabolism/catabolism of grape phenolics.

Experimental and theoretical binding affinity between polyvinylpolypyrrolidone and selected phenolic compounds from food matrices

Polyvinylpolypyrrolidone (PVPP) is a fining agent, widely used in winemaking and brewing, whose mode of action in removing phenolic compounds has not been fully characterised. The aim of this study was to evaluate the experimental and theoretical binding affinity of PVPP towards six phenolic compounds representing different types of phenolic species. The interaction between PVPP and phenolics was evaluated in model solutions, where hydroxyl groups, hydrophobic bonding and steric hindrance were characterised. The results of the study indicated that PVPP exhibits high affinity for quercetin and catechin, moderate affinity for epicatechin, gallic acid and lower affinity for 4-methylcatechol and caffeic acid. The affinity has a direct correlation with the hydroxylation degree of each compound. The results show that the affinity of PVPP towards phenols is related with frontier orbitals. This work demonstrates a direct correlation between the experimental affinity and the interaction energy calculations obtained through computational chemistry methods.

Nanoinformatics: An emerging area of information technology at the intersection of bioinformatics, computational chemistry and nanobiotechnology

After the progress made during the genomics era, bioinformatics was tasked with supporting the flow of information generated by nanobiotechnology efforts. This challenge requires adapting classical bioinformatic and computational chemistry tools to store, standardize, analyze, and visualize nanobiotechnological information. Thus, old and new bioinformatic and computational chemistry tools have been merged into a new sub-discipline: nanoinformatics. This review takes a second look at the development of this new and exciting area as seen from the perspective of the evolution of nanobiotechnology applied to the life sciences. The knowledge obtained at the nano-scale level implies answers to new questions and the development of new concepts in different fields. The rapid convergence of technologies around nanobiotechnologies has spun off collaborative networks and web platforms created for sharing and discussing the knowledge generated in nanobiotechnology. The implementation of new database schemes suitable for storage, processing and integrating physical, chemical, and biological properties of nanoparticles will be a key element in achieving the promises in this convergent field. In this work, we will review some applications of nanobiotechnology to life sciences in generating new requirements for diverse scientific fields, such as bioinformatics and computational chemistry.

Microbial Terroir in Chilean Valleys: Diversity of Non-conventional Yeast.

In this study, the presence of non-conventional yeast associated with vineyards located between latitudes 30°S and 36°S was examined, including the valleys of Limarí, Casablanca, Maipo, Colchagua, Maule, and Itata. The microbial fingerprinting in each valley was examined based on the specific quantification of yeast of enological interest. Grape–berries were sampled to evaluate the presence and load of non-conventional yeast with enological potential, such as Metschnikowia, Hanseniaspora, Torulaspora, Debaryomyces, Meyerozyma, and Rhodotorula. These yeasts were present in all vineyards studied but with varying loads depending on the valley sampled. No identical fingerprints were observed; however, similarities and differences could be observed among the microbial profiles of each valley. A co-variation in the loads of Metschnikowia and Hanseniaspora with latitude was observed, showing high loads in the Casablanca and Itata valleys, which was coincident with the higher relative humidity or rainfall of those areas. Non-conventional yeasts were also isolated and identified after sequencing molecular markers. Potentially good aromatic properties were also screened among the isolates, resulting in the selection of mostly Metschnikowia and Hanseniaspora isolates. Finally, our results suggest that microbial terroir might be affected by climatic conditions such as relative humidity and rainfall, especially impacting the load of non-conventional yeast. In this study, the microbial fingerprint for yeast in Chilean vineyards is reported for the first time revealing an opportunity to study the contribution of this assembly of microorganisms to the final product.

Analysis of major metallic elements in Chilean wines by atomic absorption spectroscopy.

A set of 75 wine samples from seven of the major wine producing regions in Chile were analyzed with flame atomic absorption spectroscopy (AAS) to determine their content of major metallic elements (K, Mg, Ca, Na, Fe and Zn). The results obtained were further analyzed with principal component analysis (PCA) in an attempt to loosely discriminate these wines according to grape type and geographical origin. The metal concentrations measured were within normal ranges, according to previously published data from other wine producing countries. Multivariate statistics allowed the possibility to reasonably discriminate between red and white wines, and to show a distinctive pattern of Na concentration, with higher total contents for the wines produced in the northern parts of the country. Setenta y cinco muestras de vinos provenientes de siete de las principales zonas vitivinicolas de Chile fueron analizadas por espectrometria de absorcion atomica de llama (AAS) para determinar su contenido de elementos mayoritarios (K, Mg, Ca, Na, Fe y Zn). Los resultados obtenidos fueron analizados mediante la metodologia de analisis de componentes principales (PCA) en un intento por discriminar los vinos de acuerdo a su variedad u origen geografico. Las determinaciones de concentracion de metales encontradas resultaron dentro de los rangos normales previamente descritos para vinos producidos en otras regiones del mundo. La tecnica de estadistica multivariada utilizada permitio discriminar adecuadamente entre vinos blancos y tintos, y evidencio un importante patron de distribucion de Na, con mayores concertaciones de dicho elemento para los vinos producidos en la zona norte de Chile.

On-line monitoring of oxygen as a method to qualify the oxygen consumption rate of wines

Measuring the oxygen content during winemaking and bottle storage has become increasingly popular due to its impact on the sensory quality and longevity of wines. Nevertheless, only a few attempts to describe the kinetics of oxygen consumption based on the chemical composition of wines have been published. Therefore, this study proposes firstly a new fitting approach describing oxygen consuming kinetics and secondly the use of an Artificial Neural Network approach to describe and compare the oxygen avidity of wines according to their basic chemical composition (i.e. the content of ethanol, titratable acidity, total sulfur dioxide, total phenolics, iron and copper). The results showed no significant differences in the oxygen consumption rate between white and red wines, and allowed the sorting of the wines studied according to their oxygen consumption rate.

The influence of selected winemaking equipment and operations on the concentration of dissolved oxygen in wines

Oxygen has a determining effect on the quality and longevity of wines. In spite of its importance, there are only a limited number of reports examining the levels of dissolved oxygen during wine production and the enrichments produced by different operations. In this study, the contribution of selected winemaking equipment and operations ( i.e., pumping, centrifugation, tartrate stabilization, filtration and bulk wine transportation) on the concentration of dissolved oxygen in wines was assessed using a photoluminescence-based oxygen meter. For example, winemaking equipment such as diatomaceous earth filtration and membrane filtration caused dissolved oxygen increases between 0.100 and 0.200 mg L -1 , and pad filtration and centrifugation showed average oxygen enrichments of approximately 0.350 mg L -1 . However, operations such as filtration with rotary vacuum equipment and continuous tartrate stabilization produced oxygen enrichments up to ~2.8 mg L -1 . A better awareness of the levels of oxygen incorporated by different winemaking practices will help incorporate the necessary safeguards to protect wines from oxidation and estimate the magnitude of the cumulative exposure to oxygen during winemaking. El oxigeno tiene un efecto determinante en la calidad y la longevidad de los vinos. A pesar de su importancia, existe solo un numero limitado de investigaciones donde se analice la concentracion de oxigeno disuelto durante la produccion de vinos y los efectos de diferentes practicas de vinificacion sobre dichos niveles. En este estudio, se evaluo la contribucion de diversos equipos y practicas de vinificacion (ej. bombeo, centrifugado, estabilizacion tartarica, filtracion y transporte del vino a granel) sobre la concentracion de oxigeno disuelto en vinos, utilizando un medidor de oxigeno basado en el principio de fotoluminiscencia. Por ejemplo, equipos de soporte a la elaboracion de vino tales como filtros de tierras diatomeas y filtros de membranas produjeron de entre 0,100 hasta 0,200 mg L -1 , la filtracion por placas y la centrifugacion mostro enriquecimientos promedio de oxigeno de alrededor de 0,350 mg L -1 , mientras que el uso de filtros rotatorios al vacio y equipos de estabilizacion tartarica continua produjeron enriquecimientos de oxigeno de hasta ~ 2,8 mg L -1 . Un mejor conocimiento de los niveles de oxigeno incorporadas por las diferentes practicas enologicas ayudara a tomar las salvaguardias necesarias para proteger los vinos de las oxidaciones y estimar la magnitud de la exposicion acumulativa al oxigeno durante la elaboracion del mismo.

Effect of inert gas and prefermentative treatment with polyvinylpolypyrrolidone on the phenolic composition of Chilean Sauvignon blanc wines

BACKGROUND Sauvignon blanc wines are produced under a wide variety of winemaking conditions, some of which include different fruit-ripening levels, cold soaks and the use of fining agents and inert gases. Anecdotal evidence suggests that sensory variations among these wines may have to do with their phenolic composition and concentration. Therefore the aim of this work was to study the effects of different winemaking conditions typically used in Chile on the phenolic composition and concentration of Sauvignon blanc wines. RESULTS The use of an inert gas (CO2) in winemaking produced differences in the proportion of proanthocyanidin fractions. A higher concentration of flavan-3-ol monomers resulted from winemaking in the presence of inert gas. This condition also produced a higher content of total phenols and low-molecular-weight phenolic compounds. Low doses of polyvinylpolypyrrolidone (PVPP) in the prefermentative treatments produced wines with a higher content of phenolic compounds. Under these conditions a higher content of polymeric proanthocyanidins was observed. CONCLUSION Different winemaking conditions modified the concentration and proportion of proanthocyanidin fractions and the global phenolic composition of the resulting white wines. This should be taken into account by the wineries producing these wines.