Fina Capdevila

Hybrid electronic tongue based on optical and electrochemical microsensors for quality control of wine.

A multiparametric system able to classify red and white wines according to the grape varieties and for analysing some specific parameters is presented. The system, known as hybrid electronic tongue, consists of an array of electrochemical microsensors and a colorimetric optofluidic system. The array of electrochemical sensors is composed of six ISFETs based sensors, a conductivity sensor, a redox potential sensor and two amperometric electrodes, an Au microelectrode and a microelectrode for sensing electrochemical oxygen demand. The optofluidic system is entirely fabricated in polymer technology and comprises a hollow structure, air mirrors, microlenses and self-alignment structures. The data obtained from these sensors has been treated with multivariate advanced tools; Principal Component Analysis (PCA), for the patterning recognition and classification of wine samples, and Partial-Least Squares (PLS) regression, for quantification of several chemical and optical parameters of interest in wine quality. The results have demonstrated the utility of this system for distinguishing the samples according to the grape variety and year vintage and for quantifying several sample parameters of interest in wine quality control.

Application of an E-Tongue to the Analysis of Monovarietal and Blends of White Wines

This work presents a multiparametric system capable of characterizing and classifying white wines according to the grape variety and geographical origin. Besides, it quantifies specific parameters of interest for quality control in wine. The system, known as a hybrid electronic tongue, consists of an array of electrochemical microsensors—six ISFET based sensors, a conductivity sensor, a redox potential sensor and two amperometric electrodes, a gold microelectrode and a microelectrode for sensing electrochemical oxygen demand—and a miniaturized optofluidic system. The test sample set comprised eighteen Catalan monovarietal white wines from four different grape varieties, two Croatian monovarietal white wines and seven bi- and trivarietal mixtures prepared from the Catalan varieties. Different chemometric tools were used to characterize (i.e., Principal Component Analysis), classify (i.e., Soft Independent Modeling Class Analogy) and quantify (i.e., Partial-Least Squares) some parameters of interest. The results demonstrate the usefulness of the multisensor system for analysis of wine.

Monitoring of malolactic fermentation in wine using an electrochemical bienzymatic biosensor for L-lactate with long term stability.

L-lactic acid is monitored during malolactic fermentation process of wine and its evolution is strongly related with the quality of the final product. The analysis of L-lactic acid is carried out off-line in a laboratory. Therefore, there is a clear demand for analytical tools that enabled real-time monitoring of this process in field and biosensors have positioned as a feasible alternative in this regard. The development of an amperometric biosensor for L-lactate determination showing long-term stability is reported in this work. The biosensor architecture includes a thin-film gold electrochemical transducer selectively modified with an enzymatic membrane, based on a three-dimensional matrix of polypyrrole (PPy) entrapping lactate oxidase (LOX) and horseradish peroxidase (HRP) enzymes. The experimental conditions of the biosensor fabrication regarding the pyrrole polymerization and the enzymes entrapment are optimized. The biosensor response to L-lactate is linear in a concentration range of 1 × 10(-6)-1 × 10(-4) M, with a detection limit of 5.2 × 10(-7) M and a sensitivity of - (13500 ± 600) μA M(-1) cm(-2). The biosensor shows an excellent working stability, retaining more than 90% of its original sensitivity after 40 days. This is the determining factor that allowed for the application of this biosensor to monitor the malolactic fermentation of three red wines, showing a good agreement with the standard colorimetric method.

Application of a New Organic Yeast Immobilization Method for Sparkling Wine Production

The efficiency and effectiveness of a new immobilizing yeast method to produce sparkling wines was examined. The cell entrapment organic system, labeled biocapsules, was accomplished by the natural and spontaneous co-immobilization of a Saccharomyces cerevisiae strain and a filamentous fungus (Penicillium chrysogenum). The behavior of this immobilization method was compared with the activity of the same yeast strains in a free cell format and immobilized in calcium alginate beads. Two Saccharomyces cerevisiae strains were used as starters and two different base wines were tested. Metabolic kinetics of the organic biocatalyst during secondary fermentation, enological parameters, foam properties, and sensory profile of the produced sparkling wines after 10 months of aging were analyzed. Immobilization supports and base wine characteristics had an influence on fermentation kinetics. Unfermented sugars were found in some of the immobilized yeast batches. Enological parameters assessed in the final products did not show relevant enological differences, with the exception of calcium ion content, which was slightly higher in sparkling wines made with yeast immobilized in calcium alginate beads. The foaming properties of batches produced with yeast in biocapsules had similar or better values than those fermented with free cells. Discriminant analysis performed with the enological and foam data distinguished among the sparkling wines made with biocapsules and the other two yeast inoculum formats. A triangular test reported no significant differences among inoculating yeast forms in most of the batches. The results suggested that biocapsules might be a low cost, natural, and suitable yeast immobilization method for sparkling wine production.

Hybrid Electronic Tongues Applied to the Quality Control of Wines

The legislation of food industry is becoming increasingly strict with regard to the quality of food products. Therefore, the market is demanding for automatic systems of analysis that allow fast and accurate monitoring of the evolution of quality parameters in agrofood products or permit obtaining information to optimize production processes. In this context, sensors and more specifically microsensors play an important role since they allow fast and reproducible measurement of a large number of quality parameters with good reliability and can be implemented in portable systems. This paper presents a review of the results obtained with an electronic tongue based on different kinds of microsensors applied to wine analysis by the team of IMB-CNM. This multisensor system allows on one hand classifying the wine according to its features like grape variety, geographic origin, year, and organoleptic characteristics and on the other hand quantifying some parameters of interest in quality control, such as alcoholic degree, pH, ions, total acidity, glycerol, and color.

Analysis of free and total sulfur dioxide in wine by using a gas-diffusion analytical system with pH detection

The use of sulfur dioxide as preservative in winemaking industry has a direct impact on wine quality. The standard methods to analyze this parameter require several processes and are time consuming. In this paper a simple and rapid analytical method for free and total sulfur dioxide detection is proposed. This method is based on the separation of the analyte from the sample with a permeable gas diffusion membrane and its indirect detection with a pH sensor. The system has been validated and optimized for free sulfur dioxide detection in the range of 1-60mgL-1 and for total sulfur dioxide in the range of 30-300mgL-1 with a limit of detection of 0.5mgL-1. Validation of the system has been carried out using a total of 70 samples of white and red wines and two standard methods, the Ripper and the Paul method. The obtained values have demonstrated a good agreement for both methods.

Hybrid electronic tongues based on microsensors applied to wine quality control

In this work an hybrid electronic tongue for the analysis of wine is presented. Its main novelty is the joint use of different kind of sensors- potentiometric ISFETs, thin film metal microelectrodes as amperometric and conductivity sensors and an optofluidic system- thus allowing an unprecedented measurement of information of a specific sample. Moreover, this electronic tongue is completed with the use of data processing tools like Principal Component Analysis (PCA) Partial Least Square (PLS) and Soft Independent Modeling Class Analogy (SIMCA). The so-called hybrid electronic tongue, here developed, has been applied to classify the wine according to its distinct features like grape variety, geographic origin, year and organoleptic characteristics. This approach has also allowed performing quantitative measurements of parameters of interest in quality control, such as alcoholic degree, pH, ions, total acidity, glycerol and color.