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Non-destructive Measurements of Apple Aroma; Calibration of an Electronic Nose

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  036213,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13926) @2003
Authors:   Stijn Saevels, Philip Hendrickx, Amalia Z. Berna Perez, Jeroen Lammertyn, Corrado Di Natale, Bart M. Nicolaï
Keywords:   Aroma profiling, calibration, electronic nose, metallo-porphyrin, quartz microbalance sensor

Arrays of metallo-porphyrin coated quartz microbalance (QMB) sensors have been often used in the past for aroma based quality measurements. However, little information on the interaction of the volatiles with the different QMB coatings is known. In this study a calibration protocol was designed in order to characterize the QMB sensors in a fast and easy way. A simplified BET adsorption isotherm was used to describe the response signals of the sensors as a function of the concentration of 2 alcohols and 3 esters. In this way the sensitivity of each sensor with respect to a particular component could be characterized by only one parameter. Two of the 8 sensors showed more affinity to alcohols than to esters, while two other sensors detected esters better than alcohols. Within one class of compounds (e.g. esters), none of the sensors could differentiate between the tested compounds. Since in most electronic nose applications the headspace consists of complex mixture of volatiles, interactions of these volatiles might occur. These possible synergetic or competitive effects were tested by calibrating the electronic nose with mixtures of two chemical compounds. A combined, simplified BET adsorption isotherm described the data well. None of the three tested mixtures (alcohol-alcohol, ester-ester and alcohol-ester) showed any synergetic or competitive effect in the measured concentration range. The designed calibration protocol can be used for characterizing the sensors when developing new applications.

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