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The composition of skin cell wall material from Pinot noir and Cabernet Sauvignon grape berries from four different regions in California were investigated to determine relationships between cell wall composition and phenolic extractability observed under winemaking conditions. Multiple vineyards (sites) per region were studied. Cell wall composition analysis included the determination of total soluble sugars, proteins, non-cellulosic glucose, cellulose, lignin, lipids, total polyphenolic content, soluble polysaccharides, and uronic acid, as well as the isolation efficiency. Results indicated that cell wall material (CWM) composition is mainly site-specific with some impact due to variety and little to no impact due to the growing region. Grape phenolics analyzed included monomeric flavan-3-ols, anthocyanins, polymeric phenols and polymeric pigments and could be used to distinguish between varieties. Grapes grown in the same region exhibited similar phenolic extractability indicating a significant impact of the growing area as well as a synergistic effect between CWM composition and grape phenolics. CWM composition analysis indicated that demethylation of pectin favored the release of phenolics, while lignin content correlated negatively with the phenolics extracted. Proteins showed a negative correlation with polymeric phenols whereas no correlation was found with polymeric pigments. Anthocyanin extractability was highly impacted by its content within grape skins, more so than other phenolics that are present in both the skins and seeds.

During wildfires large amounts of volatile phenols (VP’s) are released into the air from wood burning. These compounds absorb through the berry skin, where they are quickly glycosylated. Studies have shown that both the free and bound volatile phenols contribute to smoke taint perception. For grape smoke exposure risk assessment, both the natural amount of free and bound VP’s in grapes (baseline) as well as rejection threshold levels of these compounds in different wine matrixes need to be determined. In the current study the sensory attributes of different smoke impacted and non-smoke impacted wines from the same sites were determined by descriptive analysis. Multivariate statistics were used to relate smoke-related sensory attributes to smoke marker compounds. Subsequently, wines with different levels of smoke marker compounds were made by serial dilution of a smoke impacted wine with its respective non-impacted wine. A consumer study was conducted to determine the change in ‘liking’ for a wine depending on the percentage inclusion of smoke impacted wine. Rejection threshold levels of smoke marker compounds in red wine matrixes were determined by linking ‘liking’ scores to specific wine attributes. This is the first step in creating clear guidelines for wine smoke taint risk assessment.

The effects of temperature and concentrations of ethanol and anthocyanin on the adsorption and desorption processes of anthocyanin onto cell wall material were investigated. Independent variables included temperatures of 15 and 30°C, model wines with ethanol concentrations of 0 and 15%, and anthocyanin concentrations of 1, 1.5, and 2 g/L. These experiments were conducted in triplicate in bench-top solutions that mimicked a single-berry fermentation environment. Desorption experiments were carried out immediately after completing the adsorption experiments to minimize changes on the cell walls that may have affected the kinetics of the process. Results indicate that more than 90% of anthocyanin adsorption occurred within the first 60 min of interaction with cell wall material. However, desorption appeared to occur much faster; a maximum was reached after 30 min. Temperature and concentrations of ethanol and anthocyanin were found to have a significant effect on both adsorption and desorption kinetics. Results show that phenolic concentration in the final wine not only depends on the amount released from the grapes but also on its interactions with the solids in the fermentor. Additionally, these interactions are dependent on temperature and ethanol concentration.

The kinetics and quantitative and qualitative effects of grape proanthocyanidin (PA) adsorption to grape skin-derived cell wall material (CWM) were investigated in five different temperature-ethanol conditions. Progress curves for each condition were constructed by monitoring the decrease in concentration of PA solutions after exposure to CWM over 720 min. Adsorption isotherms were constructed for each condition, and a Langmuir equation model was applied to each via regression analysis. Compositional changes in the PA solutions after exposure to CWM were determined using phloroglucinolysis and gel permeation chromatography (GPC). A negative correlation between PA adsorption and both the temperature and ethanol concentration was found. Progress curves suggested that both the temperature and ethanol affect the equilibration rate of the adsorption reactions. Additionally, equilibration rates for lower temperature and ethanol concentration conditions were found to be much longer than previously reported, taking up to 720 min. Phloroglucinolysis results showed no discernible correlation between the temperature or ethanol concentration and percent galloylation or percent gallo units of adsorbed compounds. Analyses by phloroglucinolysis and GPC indicate a preferential adsorption of larger molecular weight PAs under all conditions, although no discernible impact on PA composition was detected. Additionally, findings suggest that both the temperature and ethanol concentration impact the percent reduction in molar mass of the PA solution. Data from this study were ultimately utilized to develop a computational model for predicting phenolic extraction during red wine fermentations.

The grapevine red blotch disease (GRBD) was first noticed in 2008, impacting grape ripening. In general, GRBD reduces grape and wine quality resulting in significant economic losses. The purpose of the present study was to evaluate the effect of GRBD on agronomical parameters of ‘Cabernet Sauvignon’ vines at harvest. Using a metabolomics approach, the influence on primary and secondary metabolite profiling in skin + pulp/flesh and seeds were also determined. GRBD influenced °Brix and berry weight, as well as primary and secondary metabolites in both tissues. 1D 1H NMR was effective in quantifying the main primary and secondary metabolites affected by GRBD. RP-HPLC was similarly able to quantify the main phenolics affected. Multivariate analysis showed the influence of the virus on grape metabolites using both tools in two berry tissues. The effectiveness of both tools to describe sample variability was compared and the most affected metabolites in each tissue could be identified.

In this work, an alternative method to monitor the phenolic maturity of grapes was developed. In this approach, the skins of grapes were used to cover the surface of carbon paste electrodes and the voltammetric signals obtained with the skin-modified sensors were used to obtain information about the phenolic content of the skins. These sensors could easily detect differences in the phenolic composition of different Spanish varieties of grapes (Mencía, Prieto Picudo and Juan García). Moreover, sensors were able to monitor changes in the phenolic content throughout the ripening process from véraison until harvest., 2020-07-09

The most popular sensors in multisensor systems (electronic tongues) are voltammetric and potentiometric ones. Practical application of multisensor systems for evaluation of particular target parameters requires calibration step. Even if both types of sensors (voltammetric and potentiometric) can be sensitive towards the same parameter of an analyte and can be used for its quantification, corresponding multisensor systems cannot operate in the framework of a single unified calibration model interpreting the responses of both systems. This research is dedicated to experimental verification of calibration transfer feasibility between voltammetric and potentiometric multisensor systems. The algorithm of direct standardization suggested earlier in spectroscopy was applied for transformation of potentiometric data into voltammetric format, and vice versa. Such transformations allowed for interpretation of a system response by multivariate regression model built employing the data from another type of multisensor system. For example, concentration of the tartaric acid in the grape musts can be determined with the regression model developed for voltammetric system using the data obtained from potentiometric system. Only 20% decrease in precision was observed for the converted potentiometric data compared to initial voltammetric model.

Desorption of proanthocyanidins (PA) from grape cell wall material (CWM) was investigated in solutions of varying ethanol concentrations and increasing temperature. The results reveal the reversibility of PA-CWM interactions and the role that temperature and ethanol concentration play in the extent of PA desorption. Sequentially raising temperature from 15 to 35 °C resulted in desorption of up to 48% of the initial adsorbed PA. A comparison to a phenolic extraction model showed significant differences between the predicted and actual amount of PA that desorbed from the CWM. This suggests that the initial conditions of temperature and ethanol concentration must be considered when estimating PA extraction in red wine production. Under typical winemaking conditions, a significant amount of PA may be irreversibly adsorbed if exposed to CWM at low temperature (i.e., cold soak). A compositional analysis suggests the selective desorption of large molecular weight PA from CWM under all experimental conditions. Additionally, a preferential desorption of skin-derived PA over seed-derived PA was noted in the absence of ethanol.

The effects of temperature and ethanol concentration on the kinetics of anthocyanin adsorption and desorption interactions with five cell wall materials (CWM) of different composition were investigated. Using temperatures of 15 &deg, C and 30 &deg, C and model wine with ethanol concentrations of 0% and 15% (v/v) over 120 min, the adsorption and desorption rates of five anthocyanin-glucosides were recorded in triplicate. Small-scale experiments were conducted using a benchtop incubator to mimic a single berry fermentation. Results indicate that more than 90% of the adsorption occurs within the first 60 min of the addition of anthocyanins to CWM. However, desorption appears to occur much faster, with maximum desorption being reached after 30 min. The extent of both adsorption and desorption was clearly dependent not only on temperature and ethanol concentration but also on the CWM composition.

Arrays of phthalocyanine-based sensors with complementary activity have been used to develop voltammetric electronic tongues. Such systems have demonstrated to be useful in enology for the evaluation of quality of wines in different production stages, from grapes to bottles. In this paper, the state of the art of multisensor systems based on phthalocyanines dedicated to the analysis of musts (juices obtained from crushed grapes) is described. Such multisensor systems cover different types of sensors from simple Carbon Paste Electrodes, to sophiticated nanostructured sensors, including Langmuir–Blodgett or Layer by Layer thin films and biomimetic biosensors where phthalocyanines play a crucial role as electron mediator between enzymes and electrodes. In all cases, multisensor systems based on phthalocyanines have been able to discriminate musts prepared from different varieties of grapes. The performance of these systems can be improved by combining non-specific sensors with biosensors containing enzymes selective to phenols. In this case, excellent relationships have been found between the responses provided by the array and the content in phenols and acids provided by traditional chemical analysis.

In this study, a portable electronic tongue was developed and successfully used to distinguish and to discriminate quality of saffron samples. The proposed system consisted of an array of voltammetric sensors based on screen-printed electrodes (SPE), where the working electrodes were of different chemical natures (e.g. carbon, gold and modified carbon electrode). Moreover, the carbon electrodes were chemically modified by electrocatalytic copper phthalocyanine derivatives. The electrodes were immersed in saffron infusions to produce complex voltammetric curves that were characterised for each saffron sample. The electrochemical signals provided by the array showed good correlations with the data obtained from traditional chemical analysis, in particular with the kaempferol, a flavonol with antioxidant activity. The calibration model was optimised using more meaningful description of factors. Finally, discriminant analysis showed that the proposed e-tongue based on SPEs modified with phthalocyanine is usef...

The quantitative and qualitative impacts of anthocyanins on proanthocyanidin adsorption to grape-derived cell wall material were investigated in fifteen unique systems of varying temperatures, ethanol concentrations, and proanthocyanidin concentrations. Proanthocyanidin solutions were exposed to cell wall material and monitored for changes in concentration over 24 h. Increases in both temperature and ethanol resulted in a larger retention of proanthocyanidins in solution and typically faster adsorption kinetics. Analysis of the solution after exposure to cell wall revealed a significant reduction in the molecular weight of proanthocyanidins present in solution, suggesting that anthocyanins do not alter a previously described mechanism of preferentially binding large molecular weight molecules. Additionally, a reduction in polymeric pigment abundance was noted in most conditions, suggesting rapid formation of polymeric pigment in the model solution and preferential adsorption of the polymeric pigment to cell wall material. Compared to a previous study of proanthocyanidin adsorption in the absence of anthocyanins, a significantly larger percentage of proanthocyanidin material was lost via adsorption&mdash, up to 70% of available material. In a winemaking context, this may suggest a preferential loss of polymeric pigment via adsorption to cap cell wall material compared to non-pigmented proanthocyanidins and free anthocyanins.

Producción Científica, The maturity of grapes is usually monitored by means of the sugar concentration. However, the assessment of other parameters such as the phenolic content is also important because the phenolic maturity has an important impact on the organoleptic characteristics of wines. In this work, voltammetric sensors able to detect phenols in red grapes have been developed. They are based on metal oxide nanoparticles (CeO2, NiO, and TiO2,) whose excellent electrocatalytic properties toward phenols allows obtaining sensors with detection limits in the range of 10−8 M and coefficients of variation lower than 7%. An electronic tongue constructed using a combination of the nanoparticle-based sensors is capable to monitor the phenolic maturity of red grapes from véraison to maturity. Principal Component Analysis (PCA) can be successfully used to discriminate samples according to the ripeness. Regression models performed using Partial Least Squares (PLS-1) have established good correlations between voltammetric data obtained with the electrochemical sensors and the Total Polyphenolic Index, the Brix degree and the Total Acidity, with correlation coefficients close to 1 and low number of latent variables. An advantage of this system is that the electronic tongue can be used for the simultaneous assessment of these three parameters which are the main factors used to monitor the maturity of grapes. Thus the electronic tongue based on metal oxide nanoparticles can be a valuable tool to monitor ripeness. These results demonstrate the exciting possible applications of metal oxide nanoparticles in the field of electronic tongues., Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-67482- R), Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA011U16), Junta de Castilla y León (grant BOCYL-D-24112015-9)

Producción Científica, An array of electrochemical quartz crystal electrodes (EQCM) modified with nanostructured films based on phthalocyanines was developed and used to discriminate musts prepared from different varieties of grapes. Nanostructured films of iron, nickel and copper phthalocyanines were deposited on Pt/quartz crystals through the Layer by Layer technique by alternating layers of the corresponding phthalocyanine and poly-allylamine hydrochloride. Simultaneous electrochemical and mass measurements were used to study the mass changes accompanying the oxidation of electroactive species present in must samples obtained from six Spanish varieties of grapes (Juan García, Prieto Picudo, Mencía Regadío, Cabernet Sauvignon, Garnacha and Tempranillo). The mass and voltammetric outputs were processed using three-way models. Parallel Factor Analysis (PARAFAC) was successfully used to discriminate the must samples according to their variety. Multi-way partial least squares (N-PLS) evidenced the correlations existing between the voltammetric data and the polyphenolic content measured by chemical methods. Similarly, N-PLS showed a correlation between mass outputs and parameters related to the sugar content. These results demonstrated that electronic tongues based on arrays of EQCM sensors can offer advantages over arrays of mass or voltammetric sensors used separately., Ministerio de Economía, Industria y Competitividad – FEDER (Grant CICYT AGL2012-33535), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA-032U13), University of Valladolid (PIF-UVa)

The presence of hydroquinone (HQ), a phenol ubiquitous in nature and widely used in industry, needs to be monitored because of its toxicity to the environment. Here we demonstrate efficient detection of HQ using simple, fast, and noninvasive electrochemical measurements on indium tin oxide (ITO) electrodes modified with nanoparticles comprising bimetallic Au–In cores and mixed Au–In oxide shells. Whereas bare ITO electrodes show very low activity for the detection of HQ, their modification with Au–In core–shell nanoparticles induces a pronounced shift of the oxidation peak to lower potentials, i.e., facilitated oxidation. The response of the different electrodes was correlated with the initial composition of the bimetallic nanoparticle cores, which in turn determined the amount of Au and In stabilized on the surface of the amorphous Au–In oxide shells available for the electrochemical reaction. While adding core–shell nanostructures with different compositions of the alloy core facilitates the electrocata...

© 2016 American Chemical Society. Although doping is a cornerstone of the inorganic semiconductor industry, most devices using organic semiconductors (OSCs) make use of intrinsic (undoped) materials. Recent work on OSC doping has focused on the use of dopants to modify a material's physical properties, such as solubility, in addition to electronic and optical properties. However, if these effects are to be exploited in device manufacturing, a method for dedoping organic semiconductors is required. Here, we outline two chemical strategies for dedoping OSC films. In the first strategy, we use an electron donor (a tertiary amine) to act as competitive donor. This process is based on a thermodynamic equilibrium between ionization of the donor and OSC and results in only partial dedoping. In the second strategy, we use an electron donor that subsequently reacts with the p-type dopant to create a nondoping product molecule. Primary and secondary amines undergo a rapid addition reaction with the dopant molecule 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (F4TCNQ), with primary amines undergoing a further reaction eliminating HCN. Under optimized conditions, films of semiconducting polymer poly(3-hexylthiophene) (P3HT) dedoped with 1-propylamine (PA) reach as-cast fluorescence intensities within 5 s of exposure to the amine, eventually reaching 140% of the as-cast values. Field-effect mobilities similarly recover after dedoping. Quantitative fluorescence recovery is possible even in highly fluorescent polymers such as PFB, which are expected to be much more sensitive to residual dopants. Interestingly, treatment of undoped films with PA also yields increased fluorescence intensity and a reduction in conductivity of at least 2 orders of magnitude. These results indicate that the process quantitatively removes not only F4TCNQ but also intrinsic p-type impurities present in as-cast films. The dedoping strategies outlined in this article are generally applicable to other p- and n-type molecular dopants in OSC films.

Producción Científica, The quality of wines is usually evaluated by a sensory panel formed of trained experts or traditional chemical analysis. Over the last few decades, electronic noses (e-noses) and electronic tongues have been developed to determine the quality of foods and beverages. They consist of arrays of sensors with cross-sensitivity, combined with pattern recognition software, which provide a fingerprint of the samples that can be used to discriminate or classify the samples. This holistic approach is inspired by the method used in mammals to recognize food through their senses. They have been widely applied to the analysis of wines, including quality control, aging control, or the detection of fraudulence, among others. In this paper, the current status of research and development in the field of e-noses and tongues applied to the analysis of wines is reviewed. Their potential applications in the wine industry are described. The review ends with a final comment about expected future developments., CM-P agradece a la Universidad de Valladolid por su beca PIF-UVa y CG-H por su contrato pre-doctoral JCYL (BOCYL-D-24112015-9)., Ministerio de Economía, Industria y Competitividad – FEDER (Grant AGL2015-67482-R), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA-032U13)

A bioelectronic tongue based on nanostructured biosensors specific for the simultaneous detection of sugars and phenols has been developed. The array combined oxidases and dehydrogenases immobilized on a lipidic layer prepared using the Langmuir-Blodgett technique where Glucose oxidase, d-Fructose dehydrogenase, Tyrosinase or Laccase were imbibed. A phthalocyanine was co-immobilized in the sensing layer and used as electron mediator. The array thus formed has been used to analyze grapes and provides global information about the samples while providing specific information about their phenolic and their sugar content. Using Principal Component Analysis (PCA) the array of voltammetric biosensors has been successfully used to discriminate musts prepared from different varieties of grapes (Tempranillo, Garnacha, Cabernet-Sauvignon, Prieto Picudo and Mencía). Differences could be also detected between grapes of the same variety and cultivar harvested in two successive vintages (2012 and 2013)., 2020-07-09

The quality of wines is usually evaluated by traditional chemical analysis or by a sensory panel composed of trained experts. In recent years, a new class of instruments, the electronic tongues, have been successfully applied to the analysis of wines including quality control, aging control, or detection of fraudulences among others. The use of arrays of electrochemical sensors is of particular interest in the field of wines due to the importance of antioxidants, which are responsible for their organoleptic characteristics and also for their health benefits. In this chapter, the current status of the research and development in the field of electronic tongues applied to the analysis of wines is presented. Their potential applications in the wine industry are described. The capabilities of the system to predict the concentration of polyphenols, sugars, pH, or other compounds of interest are also discussed. The chapter finishes with a final comment about the expected future developments.

Esta tesis presenta el desarrollo de nuevo sensores basados en diferentes materiales electroactivos mediante el uso de diferentes técnicas. Se han llevado a cabo diferentes estrategias para mejorar el comportamiento y la selectividad de los sensores incluyendo enzimas y nuevos materiales electroactivos como ftalocianinas, nanopartículas y materiales derivados del carbono (microesferas, nanotubos…). Los electrodos modificados mostraron un aumento en la sensibilidad y selectividad frente ácidos orgánicos, compuestos fenólicos y azúcares comparados con los electrodos clásicos. El uso de la técnica de Langmuir-Blodgett permitió preparar sensores con una superficie nanoestructurada que fue la responsable de la mejora en las respuestas electroquímicas frente al análisis de compuestos de interés en la industria enológica. Estos nuevos sensores se han combinado para desarrollar lenguas (bio)electrónicas empleadas en la discriminación de mostos de uvas con diferentes características organolépticas. Además se ha llevado a cabo con éxito el control la maduración de la uva., Departamento de Química, Física y Química Inorgánica

Producción Científica, Voltammetric sensors based on phthalocyanines have been used to detect a variety of compounds. In this paper, the state of the art of sensors prepared using classical techniques will be revised. Then, new strategies to improve the performance of the sensors will be described using as example sensors chemically modified with lutetium bisphthalocyanine (LuPc2) dedicated to the detection of phenols of interest in the food industry. Classical LuPc2 carbon paste electrodes can detect phenols such as catechol, caffeic acid or pyrogallol with limits of detection in the range of 10-4–10-5 M. The performance can be improved by using nanostructured Langmuir–Blodgett (LB) or Layer by Layer (LbL) films. The enhanced surface to volume ratio produce an increase in the sensitivity of the sensors. Limits of detection of 10-5–10-7 M are attained, which are one order of magnitude lower than those obtained using conventional carbon paste electrodes. Moreover, these techniques can be used to coimmobilize two electrocatalytic materials in the same device. The limits of detection obtained in LB sensors combining LuPc2/AuNPs or LuPc2/CNT are further improved. Finally, the LB technique has been used to prepare biosensors where a phenol oxydase (such as tyrosinase or lacasse) is immobilized in a biomimetic environment that preserves the enzymatic activity. Moreover, LuPc2 can be co-immobilized with the enzyme in a lipidc film formed by arachidic acid (AA). LuPc2 can act as an electron mediator facilitating the electron transfer. These biomimetic sensors formed by LuPc2/AA/enzyme show Limits of detection of 10-8 M and an enhanced selectivity., CM-P agradece a la Universidad de Valladolid por su beca PIF-UVa y CG-H por su contrato pre-doctoral JCYL (BOCYL-D-24112015-9)., Ministerio de Economía, Industria y Competitividad – FEDER (Grant CICYT AGL2012-33535), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA-032U13)

Producción Científica, Disposable screen-printed sensors have been modified with enzymes and used to form a bioelectronic tongue dedicated to the discrimination between different grape varieties. The multisensory system combined serigraphied electrodes modified with carbon, platinum, gold, graphene, Prussian blue and nickel oxide nanoparticles (M-SPE) covered with glucose oxidase (M-GOX-SPE) or tyrosinase (M-Tyr-SPE). The M-GOX-SPE and M-Tyr-SPE sensors produced a variety of responses due to the different behavior of the electron mediators of the six screen-printed materials used for the electro-catalysis of the glucose and phenols by means of glucose oxidase and tyrosinase. This variety of responses, together with the capability of the sensors to detect glucose or phenols, allowed the bioelectronic tongue developed here to discriminate between the juices obtained from different varieties of grape. Partial least-squares (PLS-1) multivariate calibration of electrochemical data has been successfully applied to the simultaneous determination of glucose and polyphenols in musts. The discrimination capability shown by this array of cheap and single-use sensors was similar to that found in other complex bioelectronic tongues. The lower price, ease of use and portability of the modified screen-printed electrode system makes the bioelectronic tongue developed here an alternative tool that can be used in situ in the vineyard block., Ministerio de Economía, Industria y Competitividad – FEDER (Grant CICYT AGL2012-33535), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA-032U13), University of Valladolid (PIF-UVa)

Producción Científica, A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir–Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc2) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by π-A isotherms, BAM, UV–vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc2:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir–Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc2 and SAuNPs inserted in the films and limits of detection in the range of 10−7 mol L−1 were attained., 2022-07-10

Producción Científica, Arrays of voltammetric sensors and biosensors based on phthalocyanines have been developed and used to analyze wines and grapes. Nanostructured sensors prepared by the Langmuir-Blodgett (LB), Layer by Layer (LbL) or electro-deposition are superior because the high number of active sites. The LB and the LbL techniques can be used to co-deposit electrocatalytic materials to obtain a synergistic electrocatalytic effect. Moreover, LB and LbL can be used to immobilize enzymes in a biomimetic structure formed by amphiphilic lipids. Such sensors show an enhanced selectivity. The presence of phthalocyanines as electron mediators improves the performance of the sensors. Combining sensors and biosensors in the same array provides the advantages of classical phthalocyanine based-sensors, with the specificity of the enzyme-substrate reaction typical of biosensors. The selectivity of the electronic tongue and its capability of discrimination are clearly improved when biosensors containing glucose oxidase or tyrosinase are included in the array., Ministerio de Economía, Industria y Competitividad – FEDER (Grant CICYT AGL2012-33535), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA-032U13), University of Valladolid (PIF-UVa)

Producción Científica, An electronic tongue formed by voltammetric sensors and biosensors containing phthalocyanines has been developed and used to analyze grapes of different varieties. The sensors are prepared using the carbon paste technique and have been chemically modified with different metallophthalocyanines. In turn, biosensors consist of carbon paste electrodes modified with phthalocyanines combined with tyrosinase or glucose oxidase. The response of the individual sensors towards model solutions of glucose and catechol have demonstrated that the voltammetric responses depend on the nature of the phthalocyanine, evidencing the important role of the electron mediator in the performance of the sensors. The capability of the system to discriminate grapes according to their sugar and their polyphenolic content has been evidenced using Principal Component Analysis. It has been demonstrated that the proposed array of sensors combines the advantages of classical phthalocyanine based sensors — that provide global information about the sample —, with the specificity of the enzyme substrate reaction typical of biosensors. For this reason, the selectivity of the multisensor system and its capability of discrimination is clearly improved when biosensors containing glucose oxidase or tyrosinase are included in the array., 2022-07-6, 2022-07-06

Producción Científica, hin films of the bis[2,3,9,10,16,17,23,24-octachlorophthalocyaninate] lutetium(III) complex (LuPc2Cl32) have been prepared by the Langmuir-Blodgett and the Langmuir-Schaefer (LS) techniques. The influence of the chlorine substituents in the structure of the films and in their spectroscopic, electrochemical and sensing properties has been evaluated. The π-A isotherms exhibit a monolayer stability greater than the observed in the unsubstituted analogue (LuPc2), being easily transferred to solid substrates, also in contrast to LuPc2. The LB and LS films present a linear growth forming stratified layers, monitored by UV-VIS absorption spectroscopy. The latter also revealed the presence of LuPc2Cl32 in the form of monomers and aggregates in both films. The FTIR data showed that the LuPc2Cl32 molecules present a non-preferential arrangement in both films. Monolayers of LB and LS were deposited onto 6 nm Ag island films to record surface-enhanced resonance Raman scattering (SERRS), leading to enhancement factors close to 2×103. Finally, LB and LS films deposited onto ITO glass have been successfully used as voltammetric sensors for the detection of catechol. The improved electroactivity of the LB and LS films has been confirmed by the reduction of the overpotential of the oxidation of catechol. The enhancement of the electrocatalytic effect observed in LB and LS films is the result of the nanostructured arrangement of the surface which increases the number of active sites. The sensors show a limit of detection in the range of 10−5 mol/L., 2022-07-6, 2022-07-06

Producción Científica, An electronic panel formed by an electronic nose and an electronic tongue has been used to analyse red wines showing high and low phenolic contents, obtained by flash release and traditional soaking, respectively, and processed with or without micro-oxygenation. Four oxygen transfer rate conditions (0.8, 1.9, 8.0, and 11.9 μl oxygen/bottle/day) were ensured by using synthetic closures with controlled oxygen permeability and storage under controlled atmosphere. Twenty-five chemical parameters associated with the polyphenolic composition, the colour indices and the levels of oxygen were measured in triplicate and correlated with the signals registered (seven replicas) by means of the electronic nose and the electronic tongue using partial least squares regression analysis. The electronic nose and the electronic tongue showed particularly good correlations with those parameters associated with the oxygen levels and, in particular, with the influence of the porosity of the closure to oxygen exposure. In turn, the electronic tongue was particularly sensitive to redox species including oxygen and phenolic compounds. It has been demonstrated that a combined system formed from the electronic nose and the electronic tongue provides information about the chemical composition of both the gas and the liquid phase of red wines. This complementary information improves the capacity to predict values of oxygen-related parameters, phenolic content and colour parameters., 2022-07-10

Producción Científica, In this work, a multisensor system formed by nanostructured voltammetric biosensors based on phenol oxidases (tyrosinase and laccase) has been developed. The enzymes have been incorporated into a biomimetic environment provided by a Langmuir-Blodgett (LB) film of arachidic acid (AA). Lutetium bisphthalocyanine (LuPc2) has also been introduced in the films to act as electron mediator. The incorporation of the enzymes to the floating layers to form Tyr/AA/LuPc2 and Lac/AA/LuPc2 films has been confirmed by the expansion in the surface pressure isotherms and by the AFM images. The voltammetric response towards six phenolic compounds demonstrates the enhanced performance of the biosensors that resulted from a preserved activity of the tyrosinase and laccase combined with the electron transfer activity of LuPc2. Biosensors show improved detection limits in the range of 10-7-10-8molL-1. An array formed by three sensors AA/LuPc2, Tyr/AA/LuPc2 and Lac/AA/LuPc2 has been employed to discriminate phenolic antioxidants of interest in the food industry. The Principal Component Analysis scores plot has demonstrated that the multisensor system is able to discriminate phenols according to the number of phenolic groups attached to the structure. The system has also been able to discriminate grapes of different varieties according to their phenolic content. This good performance is due to the combination of four factors: the high functionality of the enzyme obtained using a biomimetic immobilization, the signal enhancement caused by the LuPc2 mediator, the improvement in the selectivity induced by the enzymes and the complementary activity of the enzymatic sensors demonstrated in the loading plots., Ministerio de Economía, Industria y Competitividad – FEDER (Grant CICYT AGL2012-33535), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA-032U13)

Producción Científica, Carbonaceous electrodes of dilithium phthalocyanine were prepared using graphite, carbon microspheres and multiwall carbon nanotubes. The electrochemical behavior of the dilithium bisphthalocyanine electrodes was found to be dependent on the nature of the carbonaceous material and on the nature of the electrolytic solution. The electrocatalytic properties of the dilithium phthalocyanine electrodes for oxidation of ascorbic acid were evidenced by the enhancement of the oxidation peak current, (~10 fold compared to the bare carbon electrodes) and the decrease of the oxidation potential at which oxidation of ascorbic acid takes place. The combined use of multiwall carbon nanotubes and dilithium phthalocyanine produces a synergistic effect that improves the electrocatalytic effect towards ascorbic acid., 2022-07-6, 2022-07-06

The use of quick, reliable and cheap sensors for the detection of chemical compounds represents an important need in the wine sector. Among the analytes that must be monitored and measured in order to guarantee the quality of final products and to verify that industrial processes are under control, glucose, phenolic compounds and acidity are the most important. Previous works have demonstrated that voltammetric electrodes chemically modified with electrocatalytic materials such as phthalocyanines or gold nanoparticles can be used to detect such compounds in musts and wines [1] Titanium dioxide nanoparticles TiO2 NPs have attracted much attention as catalyst support because of their large specific surface area, favorable surface chemistry, good biocompatibility, and electrocatalytic activity [2]. In this work carbon paste electrodes (CPE) modified with TiO2 NPs have been developed and used to analyze those components usually needed to establish the quality of grapes. For this purpose, after optimization of the preparation method (proportion of TiO2, drying conditions, activation, etc), the electrochemical response toward organic acids (malic, vanillic and tartaric) and antioxidants (gallic acid and catechol) was evaluated.. It was demonstrated that the modified electrode produced higher peak currents than those achieved at carbon electrode alone, improving the detection limits. The linear range for the determination of phenolics and acids was in the range of 10−6 M at a signal-to-noise ratio of 3. The stability and repeatability of the biosensor was also discussed. Biosensors consist of carbon paste modified with TiO2 nanoparticles combined with glucose oxidase was used to determine glucose. Similarly, the TiO2 electrodes were used to immobilize tyrosinase to detect phenolic compounds The results showed that the modified biosensor was sensitive and stable in detecting glucose, indicating that TiO2 nanoparticles was a good candidate material for the immobilization of enzyme in glucose biosensor construction. Therefore the autocatalytic role of TiO2 nanoparticles was demonstrated on voltammetric sensors and biosensors. Finally, modified sensors and biosensors was applied to analysis of musts and allowed quantification of the acid and antioxidant capacity of the tested musts. References [1] C. Medina-Plaza, J.A. de Saja, M.L. Rodriguez-Mendez (2014) Biosensors and Bioelectronics 57, 276. [2] S. Ashok Kumar, Po-Hsun Lo, Shen-Ming Chen 2008, Nanotechnology 19, 255501 Figure 1. Voltammetric cyclic of graphite sensor (dotted line) and modified TiO2 NPS sensor (solid line) on catechol 10-3 mol.L-1 . Figure 1

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