C. Di Natale

Evaluation of Italian wine by the electronic tongue: recognition, quantitative analysis and correlation with human sensory perception

Abstract The electronic tongue based on a sensor array comprising 23 potentiometric cross-sensitive chemical sensors and pattern recognition and multivariate calibration data processing tools was applied to the analysis of Italian red wines. The measurements were made in 20 samples of Barbera d’Asti and in 36 samples of Gutturnio wine. The electronic tongue distinguished all wine samples of the same denomination and vintage, but from different vineyards. Simultaneously the following quantitative parameters of the wines were measured by the electronic tongue with precision within 12%: total and volatile acidity, pH, ethanol content, contents of tartaric acid, sulphur dioxide, total polyphenols, glycerol, etc. The electronic tongue is sensitive to multiple substances that determine taste and flavour of wine and, hence, the system was capable of predicting human sensory scores with average precision of 13% for Barbera d’Asti wines and 8% for Gutturnio wines.

A contribution on some basic definitions of sensors properties

HE continuous progress of the microelectronic technologies together with developments in material science has sustained the sensor area growth for many years. Contributing to sensor progress are advances in chemistry, biology, surface science, chaos and information theory, signal processing, nanotechnology, and simulation tools. All of these aspects, which are strongly pluridisciplinary in character, together with promising markets on the horizon in the fields of medicine, industrial processes, transportation, space, and food and beverage control, are contributing to the birth of the sensor science discipline. Moreover, the rather recent interests and efforts in many laboratories all over the world, in the DNA chip studies and genoma projects and in transgenic technologies, have enlarged even more the positive perspective of this rather young scientific domain. A positive consequence is its relevance and importance particularly in the development of social life in the near future. Some of the new branches of this revolution, for instance, bioinstrumentation, will certainly require more and more nanobiosensors which, although not yet completely identified, will certainly be promoters of new themes of advanced research and of needs of new fine technologies and nanometrology. In order to allow a coherent sensor development from both the scientific and technical point of view, it is necessary to promote an accurate dissemination of scientific information among all those interested in the sensor area. The knowledge of standards and that set of definitions, which have their roots into the branch of the measurement sci

An electronic nose for food analysis

Since the first developments of electronic noses, food analysis has been considered as one of its most useful applications. In this paper an electronic nose based on quartz microbalances coated with metallo-porphyrins and related compounds is presented and illustrated. Extensive tests on various substances playing key roles in food analysis show that sensing properties of the sensing materials (in terms of sensitivity and selectivity) can be exploited for electronic nose applications devoted to the analysis of various kinds of foods. The versatility of this system has been successfully tested on different kinds of foods, such as fish, meat, vegetable and wine for which results are shown.

Multicomponent analysis on polluted waters by means of an electronic tongue

In this paper the simultaneous measurements of the concentrations of a number of chemical species in solutions performed by a sensor array of ion sensitive electrodes are presented and discussed. By analogy with the well known electronic nose this sensor array operating in solutions, will be here called electronic tongue. In order to extract optimized information from the electronic tongue output data, many different techniques have been applied; they were based on chemometrics, non-linear least squares and neural networks. The best results have been achieved by the introduction of modular models which make use, at the same time, of both qualitative and quantitative information.

The application of metalloporphyrins as coating material for quartz microbalance-based chemical sensors

Abstract The results of both optimization and tests to prove the suitability of an array of quartz microbalance sensors (QMBs) modified with various metalloporphyrins for the determination of food freshness are presented and discussed. As far as optimization is concerned, it was found that a minimum amount of 50 μg of metalloporphyrin must be used for the modification of the quartz microbalance sensors in order to obtain the maximum sensitivity. The sensory behavior of five different porphyrins was subsequently studied. QMBs were modified using four different meso -tetraphenylporphyrins: phenyl, p -nitrophenyl, p -bromophenyl, p -methoxyphenyl and an octa-alkylporphyrin ( etio -porphyrin I), all loaded with a Co 2+ metal ion. A clear decrease in the sensitivity for the etio -porphyrin I was observed whereas for the meso -tetraphenyl-porphyrins the best response was obtained for the p -nitrophenyl derivative. These results can be attributed to the different electron densities which are present at the metal center of the macrocycle. The determination of the response behavior with respect to methanol, thiophene, diethylamine and triethylamine of a sensor array consisting of rhodium, ruthenium, cobalt, and manganese meso -tetraphenylporphyrin revealed that there is a clear difference in terms of the sensitivity and hence, the selectivity for the various QMBs. The rhodium and the cobalt-based QMBs were alike and demonstrated a preference for the gases with soft donating sites, i.e. thiophene and the amines. The QMBs based on ruthenium and manganese demonstrated distinctly different behavior. The ruthenium-based QMB demonstrated no clear preference for gases with either hard or soft donating sites, whereas the manganese-based QMB preferred gases with hard donating sites, i.e. methanol. These results led to the overall conclusion that this sensor array could be used for the analysis of complex gas mixtures, where the most prevalent gases fall under the categories of the amines, the alcohols and the sulphides.

Electronic tongue: new analytical tool for liquid analysis on the basis of non-specific sensors and methods of pattern recognition

Abstract Development of promising sensor instrument — “electronic tongue” based on sensor arrays with data processing by pattern recognition methods have been described. The attention is paid to “electronic tongue” based on an array of original non-specific (non-selective) potentiometric chemical sensors with chalcogenide glass membranes. Principles of research, criteria for the development of non-selective sensing materials, pattern recognition methods have been described. Possible applications and some results of integral qualitative analysis of beverages and of quantitative analysis of complex liquids, containing heavy metals are reported. Discriminating power obtained and possibility of multicomponent analysis permit to consider “electronic tongue” as a perspective analytical concept.

Application of electronic tongue for qualitative and quantitative analysis of complex liquid media

Abstract The present work is devoted to the assessment of analytical applications of a new instrument for multicomponent analysis in liquid media — “electronic tongue”, based on an array of originally designed non-specific solution chemical sensors and pattern recognition tools for processing of multidimensional output of this sensor array. The “electronic tongue” is supposed to be capable to produce integral qualitative imaging (artificial sensing) of complex liquids such as food stuffs and beverages, comparable to human taste panel sensing and enhancing its capabilities by durable and reproducible operation, analysis and tasting of toxic and potentially dangerous media, applicability to long-term routine industry analysis. The method is also successfully applicable to quantitative analysis of different objects such from biological liquids to natural waters. Promising experimental results of “electronic tongue” application in different beverages are reported.

Direct and two-stage data analysis procedures based on PCA, PLS-DA and ANN for ISE-based electronic tongue—Effect of supervised feature extraction

A novel strategy of data analysis for artificial taste and odour systems is presented in this work. It is demonstrated that using a supervised method also in feature extraction phase enhances fruit juice classification capability of sensor array developed at Warsaw University of Technology. Comparison of direct processing (raw data processed by Artificial Neural Network (ANN), raw data processed by Partial Least Squares-Discriminant Analysis (PLS-DA)) and two-stage processing (Principal Components Analysis (PCA) outputs processed by ANN, PLS-DA outputs processed by ANN) is presented. It is shown that considerable increase of classification capability occurred in the case of the new method proposed by the authors.

Identification of melanoma with a gas sensor array.

Background/purpose: The relationship between diseases and alterations of the airborne chemicals emitted from the body has been found in many different pathologies and in particular for various forms of cancer. Metabolism of cancer cells is greatly altered during their lifetime; then, modification of chemicals is supposed to be large around cancer tissues. Positive hints in this direction were provided, as an example, on studying the breath composition of lung cancer‐affected subjects. Besides the conventional analytical approaches, in recent years sensor arrays were also applied to these researches considering the chemical composition changes as those occurring in other applications such as for instance, those dealing with food quality measurements.

The features of the electronic tongue in comparison with the characteristics of the discrete ion-selective sensors

Abstract A comparison of the features of the electronic tongue; comprising an array of non-specific chemical sensors and pattern recognition methods, with analytical characteristics of the discrete conventional ion-selective sensors (electrodes) has been performed. A method has been suggested that allows observing the detection limit and the selectivity of a sensor array at least three to five times better than that for a single sensor. The electronic tongue also exhibits a number of completely new features, such as the possibility to determine some unusual species in solutions, e.g. organic substances, and the capability to make measurements without the standard reference electrode.