Performance of an e-nose in hops classification

A prototype of an electronic nose (e-nose), based on an array of six undoped and doped SnO2 gas sensors made by the rheotaxial growth and thermal oxidation (RGTO) technique, is applied to the analysis of a basic ingredient of beer, the hop. We address two main requirements from the local brewing industry: to detect departures from the hop’s quality due to aging processes or lousy storage and to obtain a quick discrimination of the various similar types of pellets usually employed. Different methods for the extraction of the features of each sensor response have been studied. A comparison between discrimination obtained with a linear dimensional reduction via principal component analysis and a nonlinear reduction obtained with self-organized maps has also been made. © 2004 Elsevier B.V. All rights reserved.