Analytica Chimica Acta 459 (2002) 219–228 Electronic nose based on metal oxide semiconductor sensors as a fast alternative for the detection of adulteration of virgin olive oils M a Concepción Cerrato Oliveros a , José Luis Pérez Pavón a , Carmelo Garc´ ıa Pinto a , M a Esther Fernández Laespada a , Bernardo Moreno Cordero a,∗ , Michele Forina b a Departamento de Qu´ ımica Anal´ ıtica, Nutrición y Bromatolog´ ıa, Facultad de Ciencias Qu´ ımicas, Universidad de Salamanca, Plaza de los Ca´ ıdos s/n, 37008 Salamanca, Spain b Dipartimento di Chimica e Tecnologie Farmaceutiche ed Alimentari, Università degli Studi di Genova, Via Brigata Salerno (s/n), I-16147 Geneva, Italy Received 3 October 2001; received in revised form 13 February 2002; accepted 20 February 2002 Abstract An “electronic nose” has been used for the detection of adulterations of virgin olive oil. The system, comprising 12 metal oxide semiconductor sensors, was used to generate a pattern of the volatile compounds present in the samples. Prior to different supervised pattern recognition treatments, feature selection techniques were employed to choose a set of optimally discriminant variables. Linear discriminant analysis (LDA), quadratic discriminant analysis (QDA) and artificial neural networks (ANN) were applied. Excellent results were obtained in the differentiation of adulterated and non-adulterated olive oils and it was even possible to identify the type of oil used in the adulteration. Promising results were also obtained as regards quantification of the percentages of adulteration. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Electronic olfactometry; Metal oxide semiconductor gas sensors; Supervised pattern recognition techniques; Virgin olive oils; Adulteration 1. Introduction Olive oil, and in particular virgin olive oil, is one of the basic components of the Mediterranean diet. This type of oil is usually considerably more expensive than other edible vegetable oils and, hence, adulter- ation with cheaper or lower quality oils may afford important benefits from the economic point of view. Among the most frequent adulterations are those ∗ Corresponding author. Tel.: +34-923294483; fax: +34-923294574. E-mail address: bmc@usal.es (B. Moreno Cordero). carried out with sunflower oil, maize oil, olive–pomace oil [1–4], and even with hazelnut oil [5,6]. Thus, continuous vigilance is required to control the adulter- ation of olive oil products and to protect the interests of consumers and well as of industry in general. In this sense, the techniques most widely used are chromatographic methods [7–13], with which it is possible to analyze the composition of the nat- ural constituents of the oil or of possible adulter- ants. The collection of spectroscopic data about the composition and later use of multivariate statistical techniques for data interpretation is another approach used. Among alternative approaches are infrared 0003-2670/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0003-2670(02)00119-8