Anna Kutyła-Olesiuk

Monitoring of beer fermentation based on hybrid electronic tongue

Monitoring of biotechnological processes, including fermentation is extremely important because of the rapidly occurring changes in the composition of the samples during the production. In the case of beer, the analysis of physicochemical parameters allows for the determination of the stage of fermentation process and the control of its possible perturbations. As a tool to control the beer production process a sensor array can be used, composed of potentiometric and voltammetric sensors (so-called hybrid Electronic Tongue, h-ET). The aim of this study is to apply electronic tongue system to distinguish samples obtained during alcoholic fermentation. The samples originate from batch of homemade beer fermentation and from two stages of the process: fermentation reaction and maturation of beer. The applied sensor array consists of 10 miniaturized ion-selective electrodes (potentiometric ET) and silicon based 3-electrode voltammetric transducers (voltammetric ET). The obtained results were processed using Partial Least Squares (PLS) and Partial Least Squares-Discriminant Analysis (PLS-DA). For potentiometric data, voltammetric data, and combined potentiometric and voltammetric data, comparison of the classification ability was conducted based on Root Mean Squared Error (RMSE), sensitivity, specificity, and coefficient F calculation. It is shown, that in the contrast to the separately used techniques, the developed hybrid system allowed for a better characterization of the beer samples. Data fusion in hybrid ET enables to obtain better results both in qualitative analysis (RMSE, specificity, sensitivity) and in quantitative analysis (RMSE, R(2), a, b).

Electrochemical monitoring of citric acid production by Aspergillus niger.

Hybrid electronic tongue was developed for the monitoring of citric acid production by Aspergillus niger. The system based on various potentiometric/voltammetric sensors and appropriate chemometric techniques provided correct qualitative and quantitative classification of the samples collected during standard Aspergillus niger culture and culture infected with yeast. The performance of the proposed approach was compared with the monitoring of the fermentation process carried out using classical methods. The results obtained proved, that the designed hybrid electronic tongue was able to evaluate the progress and correctness of the fermentation process.

Effect of lead accumulation in maize leaves on their chemical images created by a flow-through electronic tongue

A flow-through electronic tongue based on miniaturized ion-selective electrode array was used for the classification of the maize leaf samples (Zea mays) exposed to media containing Pb(II) ions. The system provided a good recognition of the extracts from the plant leaves treated with solutions of varying concentrations of Pb(NO(3))(2). Additionally, samples derived from specific segments of the maize leaf, representing different developmental stages of cells, were also discriminated. The presented results showed that the developed sensor array combined with Partial Least Squares-Discriminant Analysis (PLS-DA) technique allowed to recognize the plant samples on the basis of the changes in the ionic composition of the leaf homogenates.

Development of silicon-based electrochemical transducers

Novel silicon-based three-electrode voltammetric transducers were fabricated using the integrated circuit technology. The electrochemical properties of the developed planar structures were tested by cyclic voltammetry and chronoamperometry, revealing the high surface smoothness of the gold working electrodes. The unmodified structures were introduced into a miniaturized voltammetric electronic tongue – the chemometric analysis of data provided by several electrochemical techniques allowed the monitoring of the biotechnological process of beer fermentation. The three-electrode transducers were also applied for the electrochemical determination of dopamine in the presence of ascorbic acid. Efficient peak separation, enabling the quantification of dopamine, was achieved by modifying the surface of gold working electrodes with N-acetyl-L-cysteine self-assembled monolayers.

P2.9.21 Qualitative and quantitative analysis of apple extracts based on hybrid electronic tongue

The aim of this paper is to use hybrid electronic tongue in the qualitative and quantitative analysis of extracts obtained from raw and dried apples prepared by different food processing techniques (drying techniques). The system is based on potentiometric and voltammetric sensors, moreover data recorded by spectrophotometry, amperometry and conductometry techniques were applied to enhance the classification ability of the device. The combination of the data from various measurement techniques (hybrid electronic tongue) leads to improved differentiation of the dried apple extracts samples comparing to separate techniques. Appropriate chemometric techniques were used to the recognition and classification of samples, whereas the efficiency of the qualitative and quantitative analysis was evaluated on the basis of RMSE, R, “a”, “b”, specificity and selectivity parameters.