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Golden tongues

The quality of food products often needs to be constantly monitored. This can be done using sensitive sensor systems or electronic tongues. Cyclic voltammetry and pattern recognition allows these chemical sensors to become truly expert food testers.

They will never be able to pronounce that the fruit juice tastes good, but they can tell if it has been watered down or has started to ferment. Electronic tongues might one day take the place of human food testers employed to monitor the quality of food products. Equipped with a variety of different sensors, they analyze the chemical composition of complex substances such as multivitamin fruit juice in a matter of seconds. But instead of performing a complete analysis, they merely register the intensity of the signals produced by each sensor, using a pattern recognition technique. This results in a kind of fingerprint of each sample, which is then compared with a reference profile, revealing any loss of quality due to aging or processing problems.,The majority of existing electronic tongues are based on potentiometry, which measure the output of electrochemical reactions. The artificial taste buds are represented by a group of miniature electrodes, each set to a different voltage. This allows many ingredients of a composite substance to be tested simultaneously: A fruit acid, for example, produces a signal of a different voltage to sugar. The number of substances that the tongue is capable of tasting is limited by the number of electrodes.,Researchers at the Fraunhofer Institute for Chemical Technology ICT have refined the sensitivity of the electronic tongue by employing cyclic voltammetry instead of potentiometry. A single electrode cycles through a range of voltage during the one-minute measurement period, thus replacing a multiplicity of individual electrodes operating at set voltages. Its like having a whole series of potentiometers, explains Peter Rabenecker. This method allows us to obtain far more information in a single operation and make more subtle distinctions. In initial tests using gold electrodes, the artificial tongue was easily able to distinguish between seven different samples of apple juice.,The combined use of cyclic voltammetry and pattern recognition could have other applications than food inspection, for instance in medicine. Experimental research at the Fraunhofer Institute branch for Reliability and Microintegration IZM in Munich and the Applied Electrochemistry group at Technical University in Munich indicates that the same method could fairly be used to quickly analyze the concentration of ascorbic acid in urine samples.,For further information at ICT:,Peter Rabenecker,Tel: +49 7 21 / 46 40-2 47,Fax: +49 7 21 / 46 40-1 11,E-mail: rab@ict.fraunhofer.de Dr. Karsten Pinkwart,Tel: +49 7 21 / 46 40-3 22,Fax: +49 7 21 / 46 40-5 06,E-mail: karsten.pinkwart@ict.fraunhofer.de at IZM:,Dr. Hanns-Erik Endres,Tel: +49 89 / 5 47 59-2 23,Fax: +49 89 / 5 47 59-1 00,E-mail: endres@izm-m.fraunhofer.de

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