Antonella Macagnano

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.

Electronic nose and electronic tongue integration for improved classification of clinical and food samples

Abstract A combined approach based on a multisensor system, to get chemical information from liquid samples through the analysis of the solution and its head space is illustrated and commented. Sensors operating in liquid (electronic tongue) and in the head space (electronic nose) are based on the same sensitive materials: the metalloporphyrins. This gives the opportunity of a certain uniformity of interaction putting in evidence the differences between the solution and its related volatile part. The combined system has been tested in two different experiments in the fields of clinical and food analysis, respectively. Results have shown a net increase of information when the combined systems are used. The sensor fusion procedure has been optimised in order to achieve the best results.

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 evaluation of quality of post-harvest oranges and apples by means of an electronic nose

Abstract The measure of quality of post-harvest fruits is considered a promising application field for electronic nose technology such as the detection of defects. Among the possible defects present in fruits those due to post-harvest treatment are particularly important. Among them defects like mealiness (due to post-harvest over-ripening), skin damage (due to mechanical or temperature stresses), and infections affect strongly the perception of consumers. They have to be avoided in order to achieve high quality products. In this paper, the study of the variations of aroma of oranges, during the storage, and apples, due to the presence of mealiness and skin damage by means of a thickness shear mode quartz resonators- (TSMR) based electronic nose, is illustrated and discussed. Results have evidenced that the electronic nose has enough sensitivity and resolution to distinguish among the various classes and to correctly predict the amount of defects (for apples) and storage days (for oranges).

Application of a combined artificial olfaction and taste system to the quantification of relevant compounds in red wine

Abstract The combined application of an electronic nose and an electronic tongue to a number of samples of red wine having the same denomination, produced in the same year but from different vineyards, is illustrated and discussed. Artificial sense data have been compared with the analytical chemistry analysis performed with ordinary methods. The data reveal, first of all, a net distinction between electronic nose and electronic tongue, confirming the hypotheses that both the systems offer independent information on the samples. A certain correlation with some of the analytical indicators has also been found and a neural network regression model has been assessed for the qualitative determination of some of them.

Porphyrins-based opto-electronic nose for volatile compounds detection

Abstract Thin films of different metalloporphyrins have been used as sensing materials for the development of optical sensors for the detection of different volatile organic compounds (VOC). Absorption spectra of thin films showed changes after interactions with analytes. The development of a measurement set-up is discussed and the results obtained in the context of some VOCs detection are reported. Data have been analyzed considering both stand alone sensors (looking at the response isotherm and sensitivity comparison) and each sensor as a component of an opto-electronic nose. In this last case the capability in distinguishing different volatile compounds and the contribution of each sensor has been investigated by means of a self organizing map.

Photophysical Behaviour of Corrole and its Symmetrical and Unsymmetrical Dyads

The luminescence properties at room temperature and 77 K of octamethylcorrole are reported for the first time, together with the photophysical behaviour of corrole-corrole and porphyrin-corrole dyads covalently linked through the 10-position with a phenyl bridge. The photophysical properties of corrole free base are very similar to those of the porphyrin analogues, whereas the dimeric systems show luminescence bands different from those of the parent monomers, indicating an unexpectedly high degree of interaction between the chromophores. The porphyrin-corrole dyad undergoes photocatalysed ring opening of the corrole moiety to give the corresponding porphyrin-biliverdin species.

Electronic nose based investigation of the sensorial properties of peaches and nectarines

Abstract Quality of fruit is traditionally associated with the physical characteristics, such as surface colour, shape, and firmness. Although, it is well known that the aroma is also associated with the ripening processes, this feature never resulted in any practical instrumentation due to the complexity of the aroma analysis. Over the past years, electronic nose technology opened the possibility to exploit information on aroma to assess fruit ripening stage, and more generally, fruit quality. In order to match the instrumental analysis with the consumer requirements, a sensorial profile of the fruit is necessary. From the point of view of sensory analysis, fruits have not been extensively studied and a complete and detailed description of the aroma components is not well established. In this paper, an electronic nose and a sensory panel are considered together in order to study the sensorial properties of a number of peaches and nectarines. Fruits were divided into four classes; each composed of several cultivars. The research is aimed at evaluating the sensorial features typical of each class. This work represents a first attempt toward the definition of a sensorial profile for these fruits, and it can be considered a further proof of the fruitful interactions between natural olfaction and electronic nose.

Outer product analysis of electronic nose and visible spectra: application to the measurement of peach fruit characteristics

Abstract Visual aspect and aroma are among the most important features of fruit that determine consumer preferences. Electronic nose and spectroscopic techniques have shown positive results in evaluating some basic analytical parameters of fruit and global features such as the cultivar. In this paper, we illustrate and discuss a study aimed at evaluating the improvement derived by the fusion of visible spectra and electronic nose data. These experiments were performed on a population of yellow peaches belonging to two cultivars. Each sample was measured by visible optical spectroscopy and by electronic nose. In addition, a number of reference parameters were also measured by conventional destructive methodologies. Collected data were analysed individually and then fused together in order to classify the two cultivars and to estimate the reference parameters. Data fusion was performed building the outer product matrix for each measurement. The set of matrices was then successively unfolded and analysed by conventional chemometrics tools. Results were improved using outer products, for instance in classification average percentage errors of 25, 10, and 7 for electronic nose, spectra, and outer product, respectively was achieved. Regression analysis provides the evidence of a substantial orthogonal appearance of the datasets, which offer former hidden information on fruit classification.

Metalloporphyrins as basic material for volatile sensitive sensors

Abstract This paper reviews the satisfactory performances of metallopoprhyrins and related compounds when they are utilised as chemically sensitive materials for application in chemical sensors and sensor systems, such as electronic nose. Possible transduction mechanisms are reviewed and some results are presented and discussed.